Re: [Elecraft] Balun Designs 1:1 FCP Isolation Transformer - SOLD

[James Bennett via Elecraft]

The Balun is sold.


Jim Bennett
Folsom, CA

K7TXA (ex W6JHB as of 1/22/2021)

Being retired doesn't mean I'm not part of the work force - just that I'm not 
forced to work!



> On Jan 30, 2021, at 11:12 AM, James Bennett via Elecraft 
>  wrote:
> 
> Continuing my downsizing in preparation for a move. I’m selling a Balun 
> Designs 1:1 FCP (Folded CounterPoise) Isolation Transformer, model 1142s. 
> This is the 2kW model designed for 160 meter operation.
> 
> I used it for several years connected on one end to my K3/KPA500/KAT500 for 
> accomplishing Worked All States on 160 meters from a small city lot. The 
> antenna was an FCP designed by W0UCE (sk) and K2AV. It did it’s job but I’ve 
> taken down the antenna and most likely will not have a 160 meter antenna at 
> my new QTH - lack of trees. Thus, I’ve no need for this unit. A new one from 
> Balun Designs will run you $92 plus shipping and maybe tax. I’ll let this one 
> go for $50, shipped FREE via USPS Priority Mail - USA only.
> 
> It is in good condition with only two issues: two of the four plastic 
> mounting tabs have broken off, and there is some liquid electrical tape 
> residue at the junction of the box and the SO-239 antenna port. Photos 
> available upon request. Contact me off-list if you are interested.
> 
> As a side note, if you are thinking you’d like to get on 160 meters but don’t 
> have room for miles of radials or a 250+ foot span for a dipole, consider 
> what I used: a very modest Inverted L and one of these FCP systems under it. 
> Check out the K2AV.com  web site for information on this 
> antenna. Guy has instructions for winding and building your own FCP. I did 
> that when I put up my first Inverted L, for 80 meters. It was a learning 
> experience. However, when I decided to put up a 160 meter Inverted L, I opted 
> for a commercial version - the one I’m selling. :-)
> 
> 
> Jim Bennett
> Folsom, CA
> 
> K7TXA (ex W6JHB as of 1/22/2021)
> 
> Being retired doesn't mean I'm not part of the work force - just that I'm not 
> forced to work!
> 
> 
> 
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Re: [Elecraft] Balun Designs Model 4114T Current Balun 5K SOLD

[James Bennett via Elecraft]

The balun has been sold - thanks for your interest!

> On Jan 2, 2021, at 1:13 PM, James Bennett via Elecraft 
>  wrote:
> 
> Doing some major antenna work here. For the past 10 years I’ve been using a 
> 92 foot long doublet, up 45 feet, fed with home brew 600-ohm ladder line. 
> From the back of my K-Line / KX3 / KX2 I ran about 10 feet of Belden 9913 
> coax out the window to this balun, under the eves. From there, 110 feet of 
> that ladder line to the antenna. Worked really well but my radiation lobes 
> were not going where I wanted them and I had limited support structures. So, 
> the doublet came down this weekend and was replaced with a 40 / 30 meter 
> Skeleton-sleeve dipole.
> 
> That means this balun is excess to my needs. It is a Balun Designs model 
> 4114T 4:1 dual-core current balun; rated at 5kW - I’ve never used more than 
> 500 watts. It has an SO-239 coax connection on the unbalanced input and two 
> studs with wing nuts on the output balanced side. It’s been mounted under the 
> house eves all this time and has had very, very minimal exposure to rain. 
> Some fading can be seen on the outside of the plastic housing, and a little 
> black “gunk” from liquid electrical tape got on a small part of it - all 
> cosmetic. It is in excellent condition - I’ve never had a problem with it. 
> Photos available upon request.
> 
> If you are looking for a great, high power 4:1 current balun for your antenna 
> farm - this one would be your choice. Take a look at the BalunDesigns.com 
>  web site for this model and it’s specs. You’ll see 
> that it sells for $89.95 new plus shipping (and maybe tax).
> 
> I’ll sell this one for $55 - free shipping to any USA address - Priority Mail.
> 
> Contact me off-list if you have questions.
> 
> Payment can be PayPal (w6...@mac.com ), cash, or 
> personal check (one week to clear, please)
> 
> Tnx & 73, 
> 
> Jim Bennett / W6JHB
> Folsom, CA 
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Re: [Elecraft] Balun BL2

[Ron D'Eau Claire]

Keep in mind that the only source of the heating in the core is the RF power 
applied. Every watt used to make heat is a watt never radiated. 

A hot core will eventually reach its Curie temperature that causes the 
inductance to drop to a very low level. At that point it is no longer 
functioning as a balun, transformer or whatever.

73, Ron AC7AC



-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Walter 
Underwood
Sent: Thursday, May 26, 2016 8:46 PM
To: Elecraft List
Subject: Re: [Elecraft] Balun BL2

You might look at the “QRP” baluns from Balun Designs. They are designed for 
250 W and cost about $50. Excellent design and construction.

http://www.balundesigns.com/low-power-qrp-baluns/ 
<http://www.balundesigns.com/low-power-qrp-baluns/>

wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)

> On May 26, 2016, at 6:04 PM, jso...@comcast.net wrote:
> 
> Hello,
> I'm contemplating buying the BL2 balun. 
> It would be connected to 450-ohm transmission-line, which would go to a 
> version of W1AB's "killer-antenna", sized for 20m on a 31' jackite-pole. 
> 
> A reviewer of the BL2, on eham five years ago, commented about heat and 
> signal-loss. 
> The heat and signal-loss concern me, not at the QRP-level but higher wattage. 
> I realize it is spec'd at 250 W but how hot does it get? 
> 
> I've looked for data about insertion-loss for the BL2 and came up short 
> there. 
> Hopefully someone has measured the insertion-loss and could share that data. 
> 
> The "elecraft BL2 assembly and operating manual" has the cores as ferrite 
> material. 
> But ferrites exhibit non-linear properties, so the loss may be a function, 
> not only of frequency, but also drive-level. 
> Insertion-loss shows up as heat and that heat affects the properties of the 
> ferrite. 
> 
> As I wrote above, I'm not concerned about QRP operation. 
> If I put it into operation on FD and but take my KX3 home for the day, what 
> happens if a club-member connects his 100+ W rig to the antenna-system to 
> operate thru the night? 
> TIA for any reply. 
> 
> 73 Jerry KM3K
> KX3 #6088
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Re: [Elecraft] Balun BL2

[Vic Rosenthal 4X6GP/K2VCO]

How hot it gets is determined by 1) the SWR and 2) the configuration of 
the antenna/feedline -- how much common mode power it has to dissipate.


I have a DX Engineering balun rated 5 kW continuous and 10 kW 
intermittent which /overheated/ on some bands when running 1 kW -- until 
I added capacitance or inductance on the antenna side of the balun to 
cancel out the reactance and at the same time detune the feedline for 
common mode current. Now it stays cold.


73,
Vic, 4X6GP/K2VCO
Rehovot, Israel
http://www.qsl.net/k2vco/

On 27 May 2016 04:04, jso...@comcast.net wrote:

Hello,
I'm contemplating buying the BL2 balun.
It would be connected to 450-ohm transmission-line, which would go to a version of W1AB's 
"killer-antenna", sized for 20m on a 31' jackite-pole.

A reviewer of the BL2, on eham five years ago, commented about heat and 
signal-loss.
The heat and signal-loss concern me, not at the QRP-level but higher wattage.
I realize it is spec'd at 250 W but how hot does it get?

I've looked for data about insertion-loss for the BL2 and came up short there.
Hopefully someone has measured the insertion-loss and could share that data.

The "elecraft BL2 assembly and operating manual" has the cores as ferrite 
material.
But ferrites exhibit non-linear properties, so the loss may be a function, not 
only of frequency, but also drive-level.
Insertion-loss shows up as heat and that heat affects the properties of the 
ferrite.

As I wrote above, I'm not concerned about QRP operation.
If I put it into operation on FD and but take my KX3 home for the day, what 
happens if a club-member connects his 100+ W rig to the antenna-system to 
operate thru the night?
TIA for any reply.

73 Jerry KM3K
KX3 #6088

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Re: [Elecraft] Balun BL2

[Walter Underwood]

You might look at the “QRP” baluns from Balun Designs. They are designed for 
250 W and cost about $50. Excellent design and construction.

http://www.balundesigns.com/low-power-qrp-baluns/ 


wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)

> On May 26, 2016, at 6:04 PM, jso...@comcast.net wrote:
> 
> Hello, 
> I'm contemplating buying the BL2 balun. 
> It would be connected to 450-ohm transmission-line, which would go to a 
> version of W1AB's "killer-antenna", sized for 20m on a 31' jackite-pole. 
> 
> A reviewer of the BL2, on eham five years ago, commented about heat and 
> signal-loss. 
> The heat and signal-loss concern me, not at the QRP-level but higher wattage. 
> I realize it is spec'd at 250 W but how hot does it get? 
> 
> I've looked for data about insertion-loss for the BL2 and came up short 
> there. 
> Hopefully someone has measured the insertion-loss and could share that data. 
> 
> The "elecraft BL2 assembly and operating manual" has the cores as ferrite 
> material. 
> But ferrites exhibit non-linear properties, so the loss may be a function, 
> not only of frequency, but also drive-level. 
> Insertion-loss shows up as heat and that heat affects the properties of the 
> ferrite. 
> 
> As I wrote above, I'm not concerned about QRP operation. 
> If I put it into operation on FD and but take my KX3 home for the day, what 
> happens if a club-member connects his 100+ W rig to the antenna-system to 
> operate thru the night? 
> TIA for any reply. 
> 
> 73 Jerry KM3K 
> KX3 #6088 
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Re: [Elecraft] Balun Questions

[Bob McGraw K4TAX]

Yes, insulation does in effect cause the electrical length to change.

Case and point, construct a 1/2 wave antenna using insulated wire, put 
it up and determine the resonant frequency or point where the SWR is 
1:1.   Then take it down, carefully strip off the insulation and put it 
back in the same place.  Make the same measurements to determine 
resonant frequency or point where the SWR is 1:1.  You'll find it 
changed due to the K factor contributed by the insulation.


73
Bob, K4TAX



On 2/9/2016 1:46 PM, Dave Cole wrote:

Hi Jim,

I have been reading about your exploits with THHN, and the 100 to 50
ohm change caused by the insulation...

I am going to pick some up today and wind a choke using it, (as opposed
to enameled 14 GA copper), to see just how close to 50 ohms it will
come...  Any last minute tips?

BTW, thanks again for publishing all of your work!




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Re: [Elecraft] Balun Questions

[Dave Cole]

Hi Jim,

I have been reading about your exploits with THHN, and the 100 to 50
ohm change caused by the insulation... 

I am going to pick some up today and wind a choke using it, (as opposed
to enameled 14 GA copper), to see just how close to 50 ohms it will
come...  Any last minute tips? 

BTW, thanks again for publishing all of your work!

-- 
73's, and thanks,
Dave

For software/hardware reviews see:
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On Tue, 2016-02-09 at 10:10 -0800, Jim Brown wrote:
> I have addressed this by showing photographs of winding techniques
> for 
> coax normally used for transmitting, and for short lengths of 
> transmission line formed by taping together a pair of 4-6 ft of #12 
> THHN. There's also text that goes with it, noting that winding
> radius 
> should follow mfr recommendations for bending radius, that close
> spacing 
> should be used to lower the resonant frequency and wider spacing to 
> raise it.
> 
> Note also that the dielectric constant of outer jacket material can
> have 
> a quite significant effect on the bandwidth of ferrite chokes. For 
> example, the bandwidth of those THHN chokes is MUCH greater than
> chokes 
> would with typical RG8, RG213, RG11. Years ago, someone sent me a
> length 
> of one of the teflon coaxes and I measured some chokes. As I recall, 
> their bandwidth was lower than those wound with conventional coax.
> 
> 73, Jim K9YC
> 
> 73, Jim K9YC
> 
> On Tue,2/9/2016 7:45 AM, James Robbins wrote:
> > 
> > Good morning Jim,
> > 
> > I am wondering if you could opine about how “tightly” coax needs to
> > be 
> > wound around a torroid for balun use (or other uses, for that
> > matter)?
> > 
> > In other words, while there have been so many Elecraft postings
> > about 
> > the bending  radii of various types of coax, there is no
> > information 
> > posted about how tightly (closely) the coax needs to be wound
> > around 
> > the edge of the toroid.  (When I have wound small torroids with
> > magnet 
> > wire, the winding is tight against the core.  I’m not sure this is 
> > even possible, let alone needed, for a balun.)
> > 
> > If this is in one of your “papers”, please just refer me to the
> > paper 
> > and I’ll dig it out.
> > 
> > 73,
> > 
> > Jim Robbins
> > 
> > N1JR
> > 
> 
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Re: [Elecraft] Balun Questions

[Robert Nobis]

Hi Bob McGraw,

I agree, except on one point: I’s say 90%, rather than 75%, of the stuff we use 
and methods employed would put most of the station stuff in the trash.

73,


Bob Nobis - N7RJN
n7...@nobis.net


> On Feb 9, 2016, at 08:01, Bob McGraw K4TAX  wrote:
> 
> I'm one of the other Bob's or Robert's
> 
> Since the assembly of coax wound around a toroid doughnut style bobbin is 
> typically not exposed to vibration, such as might exist in an airplane, boat 
> or space vehicle, the use of a solid conductor coax such as RG-303 would not 
> seem to be of concern.  The more important point and my experience and as 
> related by others, the use of coax which has foam dielectric in a tight 
> radius bend has been proven or shown to be problematic.As to if the 
> manufactures bending radius dimension is being violated, I find to be of 
> little concern.
> 
> After all, as a rule, hams are noted for pushing things to the limit and then 
> some and getting buy with it.  If hams choose to "stick to the rules 100% in 
> all aspects of their stations"I'd say 75% of the stuff we use and 
> methods employed would put most of the station stuff in the trash.
> 
> 73
> Bob, K4TAX
> 
> 
> 
> 
> 
> On 2/9/2016 8:45 AM, Guy Olinger K2AV wrote:
>> Hi Bob, et al,
>> 
>> Thank you all for your careful attention.
>> 
>> I read it wrong, as several have pointed out overnight. I transposed that
>> to a percentage in my memory after reading it. One of the reasons for
>> referring people to the original material in these cases. Someone will get
>> it right.
>> 
>> That makes it two and a half hairs :>)  Doesn't appear to change the
>> argument. To me anyway the method is still a crude measurement instead of
>> watching a wide frequency scan while bending the cable along with other
>> performance specific measurements.
>> 
>> I still would not use the solid center conductor versions (RG142/303) on a
>> winding.
>> 
>> 73, Guy K2AV
>> 
>> On Tuesday, February 9, 2016, Robert Nobis  wrote:
>> 
>>> Hi Guy,
>>> 
>>> I am not sure how you arrived at the “2/1000 of an inch” figure from the
>>> ANSI spec? The spec actually says “A change in ovality from a given
>>> sample’s initial measured value of 0.010 inches or more (> 0.010)
>>> represents the point of non-acceptable bending performance.”
>>> 
>>> 
>>> 73,
>>> 
>>> 
>>> Bob Nobis - N7RJN
>>> n7...@nobis.net 
>>> 
>>> 
>>> On Feb 8, 2016, at 18:01, Guy Olinger K2AV >> > wrote:
>>> 
>>> 
>>> I also suggest that everyone carefully study the ANSI standard until it is
>>> clear what they are doing mechanically and see what they are actually
>>> measuring:
>>> 
>>> http://www.scte.org/documents/pdf/standards/ANSI_SCTE%2039%202007.pdf
>>> 
>>> The method of measuring is in section 4. They are looking for a limit of
>>> 1% surface deformity when bending.
>>> 
>>> In the case of RG400 with .195 inch OD, that would be 2/1000 of an inch
>>> (yes, that's three zeros, two one thousandths of an inch) bending deformity
>>> at the surface of the teflon jacket, or half the thickness of an average
>>> human hair.
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
> 
> 
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Re: [Elecraft] Balun Questions

[Guy Olinger K2AV]

Hi Bob, et al,

Thank you all for your careful attention.

I read it wrong, as several have pointed out overnight. I transposed that
to a percentage in my memory after reading it. One of the reasons for
referring people to the original material in these cases. Someone will get
it right.

That makes it two and a half hairs :>)  Doesn't appear to change the
argument. To me anyway the method is still a crude measurement instead of
watching a wide frequency scan while bending the cable along with other
performance specific measurements.

I still would not use the solid center conductor versions (RG142/303) on a
winding.

73, Guy K2AV

On Tuesday, February 9, 2016, Robert Nobis  wrote:

> Hi Guy,
>
> I am not sure how you arrived at the “2/1000 of an inch” figure from the
> ANSI spec? The spec actually says “A change in ovality from a given
> sample’s initial measured value of 0.010 inches or more (> 0.010)
> represents the point of non-acceptable bending performance.”
>
>
> 73,
>
>
> Bob Nobis - N7RJN
> n7...@nobis.net 
>
>
> On Feb 8, 2016, at 18:01, Guy Olinger K2AV  > wrote:
>
>
> I also suggest that everyone carefully study the ANSI standard until it is
> clear what they are doing mechanically and see what they are actually
> measuring:
>
> http://www.scte.org/documents/pdf/standards/ANSI_SCTE%2039%202007.pdf
>
> The method of measuring is in section 4. They are looking for a limit of
> 1% surface deformity when bending.
>
> In the case of RG400 with .195 inch OD, that would be 2/1000 of an inch
> (yes, that's three zeros, two one thousandths of an inch) bending deformity
> at the surface of the teflon jacket, or half the thickness of an average
> human hair.
>
>
>
>
>
>

-- 
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Re: [Elecraft] Balun Questions

[Bob McGraw K4TAX]

I'm one of the other Bob's or Robert's

Since the assembly of coax wound around a toroid doughnut style bobbin 
is typically not exposed to vibration, such as might exist in an 
airplane, boat or space vehicle, the use of a solid conductor coax such 
as RG-303 would not seem to be of concern.  The more important point and 
my experience and as related by others, the use of coax which has foam 
dielectric in a tight radius bend has been proven or shown to be 
problematic.As to if the manufactures bending radius dimension is 
being violated, I find to be of little concern.


After all, as a rule, hams are noted for pushing things to the limit and 
then some and getting buy with it.  If hams choose to "stick to the 
rules 100% in all aspects of their stations"I'd say 75% of 
the stuff we use and methods employed would put most of the station 
stuff in the trash.


73
Bob, K4TAX





On 2/9/2016 8:45 AM, Guy Olinger K2AV wrote:

Hi Bob, et al,

Thank you all for your careful attention.

I read it wrong, as several have pointed out overnight. I transposed that
to a percentage in my memory after reading it. One of the reasons for
referring people to the original material in these cases. Someone will get
it right.

That makes it two and a half hairs :>)  Doesn't appear to change the
argument. To me anyway the method is still a crude measurement instead of
watching a wide frequency scan while bending the cable along with other
performance specific measurements.

I still would not use the solid center conductor versions (RG142/303) on a
winding.

73, Guy K2AV

On Tuesday, February 9, 2016, Robert Nobis  wrote:


Hi Guy,

I am not sure how you arrived at the “2/1000 of an inch” figure from the
ANSI spec? The spec actually says “A change in ovality from a given
sample’s initial measured value of 0.010 inches or more (> 0.010)
represents the point of non-acceptable bending performance.”


73,


Bob Nobis - N7RJN
n7...@nobis.net 


On Feb 8, 2016, at 18:01, Guy Olinger K2AV > wrote:


I also suggest that everyone carefully study the ANSI standard until it is
clear what they are doing mechanically and see what they are actually
measuring:

http://www.scte.org/documents/pdf/standards/ANSI_SCTE%2039%202007.pdf

The method of measuring is in section 4. They are looking for a limit of
1% surface deformity when bending.

In the case of RG400 with .195 inch OD, that would be 2/1000 of an inch
(yes, that's three zeros, two one thousandths of an inch) bending deformity
at the surface of the teflon jacket, or half the thickness of an average
human hair.









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Re: [Elecraft] Balun Questions

[Dave Cole]

Hello Bob,

The coax could be exposed to heat when in service as a balun, so I
would respectfully disagree with you on this one point.

If you exceed the bending radius of your coax, you stand a higher
percentage chance of causing a shield to center connector short, (due
to center conductor migration), than if you don't exceed the bend
radius.  When running high power, you also stand a better chance of
heating up your core material, (and hence your coax), which makes it
easier for the center conductor to migrate, and if you have exceeded
the bend radius-- well--  we're pretty sure where it will migrate
too...

One has to pick one's fights so to speak, and I would not pick bending
radius as one of my fights...  

If you lose, it is never good when the center conductor shorts to the
shield at Kilowatt power levels.  Use loops large enough to stay within
the bending radius of your coax.  Now if this is QRP, you could
probably get away with it.

-- 
73's, and thanks,
Dave

For software/hardware reviews see:
http://www.nk7z.net

For MixW support see:
https://groups.yahoo.com/neo/groups/mixw/info

For SSTV help see:
http://groups.yahoo.com/neo/groups/MM-SSTV/info



On Tue, 2016-02-09 at 09:01 -0600, Bob McGraw K4TAX wrote:
> I'm one of the other Bob's or Robert's
> 
> Since the assembly of coax wound around a toroid doughnut style
> bobbin 
> is typically not exposed to vibration, such as might exist in an 
> airplane, boat or space vehicle, the use of a solid conductor coax
> such 
> as RG-303 would not seem to be of concern.  The more important point
> and 
> my experience and as related by others, the use of coax which has
> foam 
> dielectric in a tight radius bend has been proven or shown to be 
> problematic.As to if the manufactures bending radius dimension
> is 
> being violated, I find to be of little concern.
> 
> After all, as a rule, hams are noted for pushing things to the limit
> and 
> then some and getting buy with it.  If hams choose to "stick to the 
> rules 100% in all aspects of their stations"I'd say 75%
> of 
> the stuff we use and methods employed would put most of the station 
> stuff in the trash.
> 
> 73
> Bob, K4TAX
> 
> 
> 
> 
> 
> On 2/9/2016 8:45 AM, Guy Olinger K2AV wrote:
> > Hi Bob, et al,
> > 
> > Thank you all for your careful attention.
> > 
> > I read it wrong, as several have pointed out overnight. I
> > transposed that
> > to a percentage in my memory after reading it. One of the reasons
> > for
> > referring people to the original material in these cases. Someone
> > will get
> > it right.
> > 
> > That makes it two and a half hairs :>)  Doesn't appear to change
> > the
> > argument. To me anyway the method is still a crude measurement
> > instead of
> > watching a wide frequency scan while bending the cable along with
> > other
> > performance specific measurements.
> > 
> > I still would not use the solid center conductor versions
> > (RG142/303) on a
> > winding.
> > 
> > 73, Guy K2AV
> > 
> > On Tuesday, February 9, 2016, Robert Nobis  wrote:
> > 
> > > Hi Guy,
> > > 
> > > I am not sure how you arrived at the “2/1000 of an inch” figure
> > > from the
> > > ANSI spec? The spec actually says “A change in ovality from a
> > > given
> > > sample’s initial measured value of 0.010 inches or more (> 0.010)
> > > represents the point of non-acceptable bending performance.”
> > > 
> > > 
> > > 73,
> > > 
> > > 
> > > Bob Nobis - N7RJN
> > > n7...@nobis.net 
> > > 
> > > 
> > > On Feb 8, 2016, at 18:01, Guy Olinger K2AV  > > > wrote:
> > > 
> > > 
> > > I also suggest that everyone carefully study the ANSI standard
> > > until it is
> > > clear what they are doing mechanically and see what they are
> > > actually
> > > measuring:
> > > 
> > > http://www.scte.org/documents/pdf/standards/ANSI_SCTE%2039%202007
> > > .pdf
> > > 
> > > The method of measuring is in section 4. They are looking for a
> > > limit of
> > > 1% surface deformity when bending.
> > > 
> > > In the case of RG400 with .195 inch OD, that would be 2/1000 of
> > > an inch
> > > (yes, that's three zeros, two one thousandths of an inch) bending
> > > deformity
> > > at the surface of the teflon jacket, or half the thickness of an
> > > average
> > > human hair.
> > > 
> > > 
> > > 
> > > 
> > > 
> > > 
> 
> 
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Help: 

Re: [Elecraft] Balun Questions

[Bob McGraw K4TAX]

If one has heating issues to that magnitude, they have other more critical 
issues which should be addressed. 

Bob, K4TAX


Sent from my iPhone

> On Feb 9, 2016, at 9:24 AM, Dave Cole  wrote:
> 
> Hello Bob,
> 
> The coax could be exposed to heat when in service as a balun, so I
> would respectfully disagree with you on this one point.
> 
> If you exceed the bending radius of your coax, you stand a higher
> percentage chance of causing a shield to center connector short, (due
> to center conductor migration), than if you don't exceed the bend
> radius.  When running high power, you also stand a better chance of
> heating up your core material, (and hence your coax), which makes it
> easier for the center conductor to migrate, and if you have exceeded
> the bend radius-- well--  we're pretty sure where it will migrate
> too...
> 
> One has to pick one's fights so to speak, and I would not pick bending
> radius as one of my fights...  
> 
> If you lose, it is never good when the center conductor shorts to the
> shield at Kilowatt power levels.  Use loops large enough to stay within
> the bending radius of your coax.  Now if this is QRP, you could
> probably get away with it.
> 
> -- 
> 73's, and thanks,
> Dave
> 
> For software/hardware reviews see:
> http://www.nk7z.net
> 
> For MixW support see:
> https://groups.yahoo.com/neo/groups/mixw/info
> 
> For SSTV help see:
> http://groups.yahoo.com/neo/groups/MM-SSTV/info
> 
> 
> 
>> On Tue, 2016-02-09 at 09:01 -0600, Bob McGraw K4TAX wrote:
>> I'm one of the other Bob's or Robert's
>> 
>> Since the assembly of coax wound around a toroid doughnut style
>> bobbin 
>> is typically not exposed to vibration, such as might exist in an 
>> airplane, boat or space vehicle, the use of a solid conductor coax
>> such 
>> as RG-303 would not seem to be of concern.  The more important point
>> and 
>> my experience and as related by others, the use of coax which has
>> foam 
>> dielectric in a tight radius bend has been proven or shown to be 
>> problematic.As to if the manufactures bending radius dimension
>> is 
>> being violated, I find to be of little concern.
>> 
>> After all, as a rule, hams are noted for pushing things to the limit
>> and 
>> then some and getting buy with it.  If hams choose to "stick to the 
>> rules 100% in all aspects of their stations"I'd say 75%
>> of 
>> the stuff we use and methods employed would put most of the station 
>> stuff in the trash.
>> 
>> 73
>> Bob, K4TAX
>> 
>> 
>> 
>> 
>> 
>>> On 2/9/2016 8:45 AM, Guy Olinger K2AV wrote:
>>> Hi Bob, et al,
>>> 
>>> Thank you all for your careful attention.
>>> 
>>> I read it wrong, as several have pointed out overnight. I
>>> transposed that
>>> to a percentage in my memory after reading it. One of the reasons
>>> for
>>> referring people to the original material in these cases. Someone
>>> will get
>>> it right.
>>> 
>>> That makes it two and a half hairs :>)  Doesn't appear to change
>>> the
>>> argument. To me anyway the method is still a crude measurement
>>> instead of
>>> watching a wide frequency scan while bending the cable along with
>>> other
>>> performance specific measurements.
>>> 
>>> I still would not use the solid center conductor versions
>>> (RG142/303) on a
>>> winding.
>>> 
>>> 73, Guy K2AV
>>> 
 On Tuesday, February 9, 2016, Robert Nobis  wrote:
 
 Hi Guy,
 
 I am not sure how you arrived at the “2/1000 of an inch” figure
 from the
 ANSI spec? The spec actually says “A change in ovality from a
 given
 sample’s initial measured value of 0.010 inches or more (> 0.010)
 represents the point of non-acceptable bending performance.”
 
 
 73,
 
 
 Bob Nobis - N7RJN
 n7...@nobis.net 
 
 
 On Feb 8, 2016, at 18:01, Guy Olinger K2AV > wrote:
 
 
 I also suggest that everyone carefully study the ANSI standard
 until it is
 clear what they are doing mechanically and see what they are
 actually
 measuring:
 
 http://www.scte.org/documents/pdf/standards/ANSI_SCTE%2039%202007
 .pdf
 
 The method of measuring is in section 4. They are looking for a
 limit of
 1% surface deformity when bending.
 
 In the case of RG400 with .195 inch OD, that would be 2/1000 of
 an inch
 (yes, that's three zeros, two one thousandths of an inch) bending
 deformity
 at the surface of the teflon jacket, or half the thickness of an
 average
 human hair.
>> 
>> 
>> __
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>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Elecraft@mailman.qth.net
>> 
>> This list hosted by: http://www.qsl.net
>> Please help support this 

Re: [Elecraft] Balun suggestions

[Eric Swartz - WA6HHQ, Elecraft]

Guys - please take this off reflector until you are in agreement.

73

Eric
List Moderator
/elecraft.com/

On 2/5/2016 8:15 PM, Ron D'Eau Claire wrote:

Gee, Wes. It's only basic RF engineering.

If you'd care to be specific about any objection, please do so. I'll be glad
to get into details on or off the reflector.

73, Ron AC7AC

-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Wes
(N7WS)
Sent: Thursday, February 4, 2016 4:18 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] Balun suggestions

I just pinched myself; I'm not dreaming and it's not April 1st, so I guess
you're serious.

You are also so wrong on so many points, I'm not going to waste time trying
to refute or correct them.

Jim, please ignore everything said below.

Wes  N7WS



On 2/4/2016 3:05 PM, Ron D'Eau Claire wrote:

Your feed line will do the job by itself so no additional "balun" is

needed.

Keep in mind that a 1:1 balun is really just a length of feed line,
usually wound on a toroidal core to make the required length shorter
than if it was in open air. The "old-school" baluns were just a pair of

air wound coils.

If your balanced feed line is at least 1/4 wavelength long, the
currents will be "balanced" (equal and out of phase) at the antenna.
That assumes your antenna is perfectly balanced to provide a perfectly
balanced load, which "balanced" antennas almost never do. There are
just too many variables. So expect excellent results even with shorter
feed lines. The amount of radiation (or pickup) from the feed line
even at the rig end is small in any case.

Connect one side of the open wire feed line to the KAT100 SO-239
center pin and the other to the KAT100 ground terminal.

73, Ron AC7AC



-Original Message-
K2/100 and KAT100 here.

I am changing around my modest antenna configuration now.  I have been
using the K2/100 with my AH-4, and now wish to use the KAT100 with
balanced feedline antennas.

What balun, homebrew or commercial, if any, should I use?  I almost
always run 5 watts, all CW.

73 de W6OGC Jim Allen


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Re: [Elecraft] Balun suggestions

[Eric Swartz - WA6HHQ, Elecraft]

Ignore my last - I mistakenly replied to an old email.

Eric
/elecraft.com/

On 2/9/2016 1:04 PM, Eric Swartz - WA6HHQ, Elecraft wrote:

Guys - please take this off reflector until you are in agreement.

73

Eric
List Moderator
/elecraft.com/

On 2/5/2016 8:15 PM, Ron D'Eau Claire wrote:

Gee, Wes. It's only basic RF engineering.

If you'd care to be specific about any objection, please do so. I'll be glad
to get into details on or off the reflector.

73, Ron AC7AC

-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Wes
(N7WS)
Sent: Thursday, February 4, 2016 4:18 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] Balun suggestions

I just pinched myself; I'm not dreaming and it's not April 1st, so I guess
you're serious.

You are also so wrong on so many points, I'm not going to waste time trying
to refute or correct them.

Jim, please ignore everything said below.

Wes  N7WS



On 2/4/2016 3:05 PM, Ron D'Eau Claire wrote:

Your feed line will do the job by itself so no additional "balun" is

needed.

Keep in mind that a 1:1 balun is really just a length of feed line,
usually wound on a toroidal core to make the required length shorter
than if it was in open air. The "old-school" baluns were just a pair of

air wound coils.

If your balanced feed line is at least 1/4 wavelength long, the
currents will be "balanced" (equal and out of phase) at the antenna.
That assumes your antenna is perfectly balanced to provide a perfectly
balanced load, which "balanced" antennas almost never do. There are
just too many variables. So expect excellent results even with shorter
feed lines. The amount of radiation (or pickup) from the feed line
even at the rig end is small in any case.

Connect one side of the open wire feed line to the KAT100 SO-239
center pin and the other to the KAT100 ground terminal.

73, Ron AC7AC



-Original Message-
K2/100 and KAT100 here.

I am changing around my modest antenna configuration now.  I have been
using the K2/100 with my AH-4, and now wish to use the KAT100 with
balanced feedline antennas.

What balun, homebrew or commercial, if any, should I use?  I almost
always run 5 watts, all CW.

73 de W6OGC Jim Allen


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Re: [Elecraft] Balun Questions

[Jim Brown]

I have addressed this by showing photographs of winding techniques for 
coax normally used for transmitting, and for short lengths of 
transmission line formed by taping together a pair of 4-6 ft of #12 
THHN. There's also text that goes with it, noting that winding radius 
should follow mfr recommendations for bending radius, that close spacing 
should be used to lower the resonant frequency and wider spacing to 
raise it.


Note also that the dielectric constant of outer jacket material can have 
a quite significant effect on the bandwidth of ferrite chokes. For 
example, the bandwidth of those THHN chokes is MUCH greater than chokes 
would with typical RG8, RG213, RG11. Years ago, someone sent me a length 
of one of the teflon coaxes and I measured some chokes. As I recall, 
their bandwidth was lower than those wound with conventional coax.


73, Jim K9YC

73, Jim K9YC

On Tue,2/9/2016 7:45 AM, James Robbins wrote:


Good morning Jim,

I am wondering if you could opine about how “tightly” coax needs to be 
wound around a torroid for balun use (or other uses, for that matter)?


In other words, while there have been so many Elecraft postings about 
the bending  radii of various types of coax, there is no information 
posted about how tightly (closely) the coax needs to be wound around 
the edge of the toroid.  (When I have wound small torroids with magnet 
wire, the winding is tight against the core.  I’m not sure this is 
even possible, let alone needed, for a balun.)


If this is in one of your “papers”, please just refer me to the paper 
and I’ll dig it out.


73,

Jim Robbins

N1JR



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Re: [Elecraft] Balun Questions

[Dave Cole]

Thank you Bob...
-- 
73's, and thanks,
Dave

For software/hardware reviews see:
http://www.nk7z.net

For MixW support see:
https://groups.yahoo.com/neo/groups/mixw/info

For SSTV help see:
http://groups.yahoo.com/neo/groups/MM-SSTV/info



On Tue, 2016-02-09 at 14:28 -0600, Bob McGraw K4TAX wrote:
> Yes, insulation does in effect cause the electrical length to change.
> 
> Case and point, construct a 1/2 wave antenna using insulated wire,
> put 
> it up and determine the resonant frequency or point where the SWR is 
> 1:1.   Then take it down, carefully strip off the insulation and put
> it 
> back in the same place.  Make the same measurements to determine 
> resonant frequency or point where the SWR is 1:1.  You'll find it 
> changed due to the K factor contributed by the insulation.
> 
> 73
> Bob, K4TAX
> 
> 
> 
> On 2/9/2016 1:46 PM, Dave Cole wrote:
> > Hi Jim,
> > 
> > I have been reading about your exploits with THHN, and the 100 to
> > 50
> > ohm change caused by the insulation...
> > 
> > I am going to pick some up today and wind a choke using it, (as
> > opposed
> > to enameled 14 GA copper), to see just how close to 50 ohms it will
> > come...  Any last minute tips?
> > 
> > BTW, thanks again for publishing all of your work!
> > 
> 
> 
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Re: [Elecraft] Balun Questions

[Jim Brown]

On Tue,2/9/2016 11:46 AM, Dave Cole wrote:

Hi Jim,

I have been reading about your exploits with THHN, and the 100 to 50
ohm change caused by the insulation...


Note that my observations are confirming results published several 
decades ago by Jerry Sevick, W2FMI. My observations of Zo and Vf are on 
the basis of measurements using a VNA and exporting data to AC6LA's 
ZPlots Excel spreadsheet.  I consider my data good to about 15% for Zo 
and 10% for Vf.



I am going to pick some up today and wind a choke using it, (as opposed
to enameled 14 GA copper), to see just how close to 50 ohms it will
come...  Any last minute tips?


You may have been confused by my writing. Enameled wire tends close to 
50 ohms, THHN in the range of 85-100 ohms.


73, Jim
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Re: [Elecraft] Balun Questions.

[Dave B via Elecraft]

On 09/02/16 17:15, elecraft-requ...@mailman.qth.net wrote:



> If you lose, it is never good when the center conductor shorts to the
>shield at Kilowatt power levels.  Use loops large enough to stay within
>the bending radius of your coax.  Now if this is QRP, you could
>probably get away with it.


There are coax cables out there that can run safely too hot to handle.   
Teflon dielectric and FEP outer cover.


It's used in multi kW industrial amps and power combiners, wrapped 
around many ferrite cores, often with fan cooling, for the ferrite, not 
the cable!


Commercial (Broadcast) baluns too are sometimes immersed in oil, much 
like power transformers, for cooling.  That's at the 10's of kW power 
level.   But the coax is the high temperature stuff again.


Use suitable cable for the job, not cheap polyethylene stuff.

Dave G0WBX.

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Re: [Elecraft] Balun Questions.

[Dave Cole]

Hi Dave G0WBX,
I used to deal with some of those prior to retirement, worked in a
broadcast shop for about 40 years...  What a difference digital has
made to TV broadcast! :)
-- 
73's, and thanks,
Dave

For software/hardware reviews see:
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On Tue, 2016-02-09 at 17:54 +, Dave B via Elecraft wrote:
> On 09/02/16 17:15, elecraft-requ...@mailman.qth.net wrote:
> 
> 
> > > If you lose, it is never good when the center conductor shorts to
> > > the
> > > shield at Kilowatt power levels.  Use loops large enough to stay
> > > within
> > > the bending radius of your coax.  Now if this is QRP, you could
> > > probably get away with it.
> 
> There are coax cables out there that can run safely too hot to
> handle.   
> Teflon dielectric and FEP outer cover.
> 
> It's used in multi kW industrial amps and power combiners, wrapped 
> around many ferrite cores, often with fan cooling, for the ferrite,
> not 
> the cable!
> 
> Commercial (Broadcast) baluns too are sometimes immersed in oil,
> much 
> like power transformers, for cooling.  That's at the 10's of kW
> power 
> level.   But the coax is the high temperature stuff again.
> 
> Use suitable cable for the job, not cheap polyethylene stuff.
> 
> Dave G0WBX.
> 
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Re: [Elecraft] Balun Questions

[Wes (N7WS)]

Bob,

It appears that you're of a mind that the winding (coax) is tightly wound around 
the core.  That's not how some guys are doing it.  It's just loosely looped 
through the core. See fig. 36 in Jim's paper.


Wes


On 2/7/2016 10:03 PM, Bob McGraw K4TAX wrote:
I am speaking of the radius of the coax bend.   To have a coax bend radius of 
3" the torroid would be huge...the size of a large coffee can.  A 3" OD, x 
1.5" ID   torroid would typically have a winding radius of less than ~1", even 
with 2 stacked cores.For my "ugly balun" project I use 4" ID PVC which has 
an OD of ~4.5" and which provides a bend radius of 2.25".


73
Bob, K4TAX



On 2/7/2016 10:32 PM, Chuck Catledge wrote:
It’s quite practical to use 25 to 35 mm radius bends of RG400 for large 
ferrite cores including both the one-piece and the snap-on varieties.  RG400 
has the same diameter as RG-58, i.e. 0.195”.  See K9YC’s tutorial here:


http://audiosystemsgroup.com/RFI-Ham.pdf

All of the RF common mode chokes I have made using small cable (i.e. RG400 
through RG6) use radii of 1-3 inches with the RG6 tending toward 3” and 
greater due to the foam dielectric.


---

Chuck, AE4CW

From: Mel Farrer [mailto:farrerfo...@yahoo.com]

Subject: Re: [Elecraft] Balun Questions


SORRY, but the min static bending radius for RG-303 is 25 mm and RG-400 is 35 
mm.  For torroid wrap which is better?






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Re: [Elecraft] Balun Questions

[Jim Brown]

On Mon,2/8/2016 2:52 PM, Mel Farrer via Elecraft wrote:

Let's do some basic thinking.


Mel,

You need to study my tutorial. Common mode chokes are NOT inductors, 
they are parallel resonant circuits, and it is their resistive impedance 
at resonance that makes the choke effective.


73, Jim K9YC
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Re: [Elecraft] Balun Questions

[Robert Nobis]

Hi Guy,

Thank you.  It is interesting that the ANSI test is based on physical “outer 
surface" deformity, rather than electrical (rf) performance. Although there is 
probably a degree of correlation between physical deformity and electrical (rf) 
performance. I agree the ANSI spec outlines a rather crude test. 

The data I provided came from several manufacturers of coax. I just wanted to 
point out that the manufacturer’s specifications for both RG303 and RG400 are 
the same at a 1.0 inch static bending radius. They did not indicate how they 
came up with these specifications. I believe there is plenty of margin in these 
specified values that may be required for use in military applications, since 
both cables are MIL spec rated. However, for ham radio purposes, I believe 
these specs can be safely ignored, within reason. Although, I probably would 
not try to bend either RG303 or RG400 any tighter than maybe 0.40 to 0.45 
inches. 

I have used RG303/U because that is what I had. If I had RG400/U, I would have 
used that. In my case, I have seen no measurable performance issues with the 
tightly wound chokes that I have made with RG303/U.  If care is taken in 
winding the chokes, I feel either type of coax will do the job. Maybe if I find 
some RG400/U at the next hamfest I attend, I will buy some and try it. I could 
then compare results.

It would be interesting to do some actual tests of the electrical impact of 
bending coax at radii needed for 2.4 inch OD cores, either single or stacked.  
Possibly some type of TDR test could be done to see if any deformaty would 
impact performance of the coax used in chokes, over the HF ham bands.

Again, thanks for sharing your insight and experience.

73,

Bob Nobis - N7RJN
n7...@nobis.net


> On Feb 8, 2016, at 18:01, Guy Olinger K2AV  wrote:
> 
> Robert Nobis wrote:
> > After reviewing specs from several manufacturers, the “recommended” minimum 
> > bend radius for RG303 and RG400 is essentially the same at 1.0 inches.  
> 
> Hi Robert, 
> 
> I have wrapped RG400 on a two stack of FT240 form factor toroids with never 
> an issue, without any change in electrical characteristics I could measure. 
> These were a little less than a half inch radius, something I would never try 
> with 303 or 142. 
> 
> A one inch radius or two inch diameter winding, per the listings you have 
> quoted, would hang loose on most forms. In effect this specifies the 
> 303/142/400 cables useless for winding on toroid cores of any HF suitable 
> size in use by hams, including even the monumental T500A series toroids.
> 
> ***However,***
> 
> I respectfully suggest that the minimum bending radius that you see published 
> for RG400 can be ignored for ham purposes at HF and low VHF, and common sense 
> is better suited to the problem. IMHO the ANSI standard (ANSI/SCTE 39 2007) 
> uses a crude method better suited to measuring metallic sheathed cables, and 
> ignores testing the needed characteristics directly, simply to avoid testing 
> cost and complexity.  
> 
> I also suggest that everyone carefully study the ANSI standard until it is 
> clear what they are doing mechanically and see what they are actually 
> measuring:
> 
> http://www.scte.org/documents/pdf/standards/ANSI_SCTE%2039%202007.pdf 
> 
> 
> The method of measuring is in section 4. They are looking for a limit of 1% 
> surface deformity when bending. 
> 
> In the case of RG400 with .195 inch OD, that would be 2/1000 of an inch (yes, 
> that's three zeros, two one thousandths of an inch) bending deformity at the 
> surface of the teflon jacket, or half the thickness of an average human hair. 
> 
> Anyone who works with teflon knows that the teflon jacket on the outside of 
> the bend will stretch and the teflon on the inside of the bend will bunch, 
> due to the difference in the radius, and particularly due to it being a soft 
> material with no constraint to its outside surface. And there is the problem 
> of managing to measure the thickness of something soft like teflon so as not 
> to compress the teflon 2 mils during the measurement of something with a 
> curved surface. 
> 
> The teflon dielectric between the inside of the shield and the center 
> conductor, all we care about, is confined by the double shield, which opposes 
> the teflon's tendency to deform. Further, the difference in the radius is 
> smaller inside the shield, dividing down the differential measured at the 
> surface of the jacket.
> 
> The 19 strand center conductor in RG400 will easily follow the teflon in 
> multiple bendings. The solid center conductor versions (303,142) to a degree 
> will remember their first bend and will apply that deformity in the second 
> and later bends, accumulating deformity at that point in the cable unless the 
> second bend is identical to the first. That is why you see "once" or "bend 
> once" in some of the listings for 

Re: [Elecraft] Balun Questions

[Richard Fjeld]

This doesn't answer your details, but what I did to test the one I made 
was simply to compare it to the balun in my manual roller inductor 
tuner. I used a short coax jumper between the tuner and the homebrew balun.


Dick, n0ce

On 2/6/2016 12:06 PM, Jim Allen wrote:

Ok, so this morning, I went out to the shack and whipped up a balun, from a G3TXQ 
design I found on the website of W5DXP.com.  It is coax wrapped around a ferrite 
core, with appropriate connectors in a plastic weathertight box.  I used RG8X coax, 
a 2.4" core, not sure exactly what mix, and 11 turns.

How do I test this device to get its properties, impedance at various 
frequencies, etc?




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Re: [Elecraft] Balun Questions

[Mel Farrer via Elecraft]

Let's do some basic thinking. The balun you made with a ferrite torroid and a 
length of coax is a straight piece of coax with the two ends supposedly 
isolated for CMC common mode current., right?  How do you make a simple 
measurement on the lowest frequency?  Expensive equipment, right?  Well, what 
is the next best way to determine the isolation at RF, Hummm.  If I measure the 
inductance across the two ends of the balun that is shield to shied to make it 
easy,  the ferrite increases the inductance of the many turns through the core, 
right?   If you take the number in uH and put it into the: ( Xl= 
6.28*F(HZ)*inductance(H)), formula you get an equivalent reactance in ohms at 
the frequency of interest.  Yes, I know there are other factors, but it gives 
you a figure of merit against any other current choke baluns, or other designs 
you would like to try. Remember More is better.    Funn.
Mel, K6KBE


  From: Richard Fjeld <rpfj...@outlook.com>
 To: elecraft@mailman.qth.net 
 Sent: Monday, February 8, 2016 12:57 PM
 Subject: Re: [Elecraft] Balun Questions
   
This doesn't answer your details, but what I did to test the one I made 
was simply to compare it to the balun in my manual roller inductor 
tuner. I used a short coax jumper between the tuner and the homebrew balun.

Dick, n0ce

On 2/6/2016 12:06 PM, Jim Allen wrote:
> Ok, so this morning, I went out to the shack and whipped up a balun, from a 
> G3TXQ design I found on the website of W5DXP.com.  It is coax wrapped around 
> a ferrite core, with appropriate connectors in a plastic weathertight box.  I 
> used RG8X coax, a 2.4" core, not sure exactly what mix, and 11 turns.
>
> How do I test this device to get its properties, impedance at various 
> frequencies, etc?
>
>

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Re: [Elecraft] Balun Questions

[Guy Olinger K2AV]

Robert Nobis wrote:
> After reviewing specs from several manufacturers, the “recommended”
minimum bend radius for RG303 and RG400 is essentially the same at 1.0
inches.

Hi Robert,

I have wrapped RG400 on a two stack of FT240 form factor toroids with never
an issue, without any change in electrical characteristics I could measure.
These were a little less than a half inch radius, something I would never
try with 303 or 142.

A one inch radius or two inch diameter winding, per the listings you have
quoted, would hang loose on most forms. In effect this specifies the
303/142/400 cables useless for winding on toroid cores of any HF suitable
size in use by hams, including even the monumental T500A series toroids.

***However,***

I respectfully suggest that the minimum bending radius that you see
published for RG400 can be ignored for ham purposes at HF and low VHF, and
common sense is better suited to the problem. IMHO the ANSI standard
(ANSI/SCTE 39 2007) uses a crude method better suited to measuring metallic
sheathed cables, and ignores testing the needed characteristics directly,
simply to avoid testing cost and complexity.

I also suggest that everyone carefully study the ANSI standard until it is
clear what they are doing mechanically and see what they are actually
measuring:

http://www.scte.org/documents/pdf/standards/ANSI_SCTE%2039%202007.pdf

The method of measuring is in section 4. They are looking for a limit of 1%
surface deformity when bending.

In the case of RG400 with .195 inch OD, that would be 2/1000 of an inch
(yes, that's three zeros, two one thousandths of an inch) bending deformity
at the surface of the teflon jacket, or half the thickness of an average
human hair.

Anyone who works with teflon knows that the teflon jacket on the outside of
the bend will stretch and the teflon on the inside of the bend will bunch,
due to the difference in the radius, and particularly due to it being a
soft material with no constraint to its outside surface. And there is the
problem of managing to measure the thickness of something soft like teflon
so as not to compress the teflon 2 mils during the measurement of something
with a curved surface.

The teflon dielectric between the inside of the shield and the center
conductor, all we care about, is confined by the double shield, which
opposes the teflon's tendency to deform. Further, the difference in the
radius is smaller inside the shield, dividing down the differential
measured at the surface of the jacket.

The 19 strand center conductor in RG400 will easily follow the teflon in
multiple bendings. The solid center conductor versions (303,142) to a
degree will remember their first bend and will apply that deformity in the
second and later bends, accumulating deformity at that point in the cable
unless the second bend is identical to the first. That is why you see
"once" or "bend once" in some of the listings for RG303 and RG142. I have
no argument with the "bend once" specification in the 303 and 142 listings.
It's relates to the reason I use RG400.

RG400 is the only coax listed for certified aircraft installations in a lot
of aircraft service vendor's web pages. I find 142 mentioned a few times as
being easier to fit with connectors. I have not seen 303 mentioned on an
aircraft service vendor web page.

73, Guy K2AV
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Re: [Elecraft] Balun Questions

[Pete Michaelis - N8TR]

At 01:07 AM 2/7/2016, K2AV wrote:


I also came by bundles of miscellaneous 6 foot to 15 foot jumpers with
various connectors on end for similar ridiculous low prices per foot.


In the last few years I have found similar RG400 jumpers at the Dayton
Hamvention at quite reasonable prices.  Since I use RG400 exclusively
for making chokes, short lengths are fine.

73, Pete - N8TR

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Re: [Elecraft] Balun Questions

[Chuck Catledge]

At hamfests around the Southeast, surplus RG400 is often found in terminated 
cables (usually BNC or N) in lengths up to around 20 feet.  The price I've paid 
is always less than $1.00 per foot, sometimes much less.  I've used it to make 
dozens of RF chokes (1:1 baluns).  The small size of RG400 allows the use of a 
single medium to large clamp-on #31 ferrite that works effectively from 
10-160M, conditioned by the number of turns.  The large snap-on ferrite will 
accommodate 10-12 turns; the medium snap-on will handle 5-6 turns.  Jim, K9YC's 
tutorials are excellent.  Consult the Fair-Rite website for additional 
technical data.

BTW, the Teflon dielectric allows easy soldering in PL-259s with RG-58 reducers 
without any fear of melting the dielectric.
---
Chuck, AE4CW

-Original Message-
From: Guy Olinger K2AV [mailto:k2av@gmail.com] 
Sent: Sunday, February 07, 2016 01:08
To: Robert Nobis <n7...@nobis.net>
Cc: elecraft@mailman.qth.net; Ron D'Eau Claire <r...@cobi.biz>; Guy Olinger 
K2AV <k2av@gmail.com>
Subject: Re: [Elecraft] Balun Questions

RG303 is not rated for the tight bends.  RG400 with its fine stranded center 
conductor is rated for corner bends in aircraft wiring harnesses and will not 
deform the dielectric within the bends. I would not wind any solid center 
conductor coax on a toroid.

I would only buy cut lengths of RG400 after the lengths for a project are 
known. Some number of such suppliers on eBay. One currently listed at 1.98 per 
foot:
http://www.ebay.com/itm/RG400-Coaxial-Cable-Mil-spec-by-the-ft-US-supplier-/251260159394?hash=item3a8045c5a2:g:WpAAAOxy43FRafUe

True it ain't ham cheep. The good stuff that lasts and lasts almost never is. 
Back in the early days of eBay I came by a 142' length of RG400 for $25. That's 
$0.178  a foot  I also came by bundles of miscellaneous 6 foot to 15 foot 
jumpers with various connectors on end for similar ridiculous low prices per 
foot.

The silvered copper strands stand up to migration of dampness in a way not 
possible with same size copper strands minus the silvering. I have
*measured* the dry RF resistance at 1.83 MHz of a 67 foot length of corroded 
#14 stranded plain copper at 62 ohms. When new this wire had resistance at RF 
of less than an ohm. I have never found the silvered copper equivalent in 
anything remotely approaching that degraded state.

RG400 wound on the proper core for the job will last a lifetime.

73, Guy K2AV

On Saturday, February 6, 2016, Robert Nobis <n7...@nobis.net> wrote:

> I have used RG303/U for chokes.  A bit smaller diameter than RG400 
> (0.170 versus 0.195 inches). RG303/U has a solid copper center 
> conductor that is silver plated.  The shield for RG303 is also silver 
> plated copper. The jacket is Class 9 Teflon. Also the dielectric material is 
> teflon.
>
> 73,
>
>
> Bob Nobis - N7RJN
> n7...@nobis.net
>
>
> > On Feb 6, 2016, at 17:49, Guy Olinger K2AV <k2av@gmail.com> wrote:
> >
> > If one wants a small 50 ohm coax that will take QRO with a very 
> > large margin and was *designed* for bending and use in aircraft 
> > wiring
> harnesses
> > then use RG400 to wind around your core. RG400 uses a fine stranded 
> > silvered copper center conductor that is more flexible than its 
> > Teflon dielectric. It has a double shield made from silvered copper strands.
> >
>
>
>


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Re: [Elecraft] Balun Questions

[Robert Nobis]

Mel,

I have seen comparable specs on RG303 versus RG400, however, some cable 
manufacturers have specified a larger bending radius for both cables. Not sure 
why?

I wonder if anyone has actually run tests of coax showing the real impact of 
bending with a small radius, comparable to what one would see in a typical 
common mode choke?

73

Bob Nobis - N7RJN
n7...@nobis.net


> On Feb 7, 2016, at 15:53, Mel Farrer <farrerfo...@yahoo.com> wrote:
> 
> SORRY, but the min static bending radius for RG-303 is 25 mm and RG-400 is 35 
> mm.  For torroid wrap which is better?
> 
> Mel, K6KBE
> 
> 
> From: Chuck Catledge <ae...@att.net>
> To: 'Guy Olinger K2AV' <k2av@gmail.com>; 'Robert Nobis' <n7...@nobis.net> 
> Cc: elecraft@mailman.qth.net; 'Ron D'Eau Claire' <r...@cobi.biz>
> Sent: Sunday, February 7, 2016 2:31 PM
> Subject: Re: [Elecraft] Balun Questions
> 
> At hamfests around the Southeast, surplus RG400 is often found in terminated 
> cables (usually BNC or N) in lengths up to around 20 feet.  The price I've 
> paid is always less than $1.00 per foot, sometimes much less.  I've used it 
> to make dozens of RF chokes (1:1 baluns).  The small size of RG400 allows the 
> use of a single medium to large clamp-on #31 ferrite that works effectively 
> from 10-160M, conditioned by the number of turns.  The large snap-on ferrite 
> will accommodate 10-12 turns; the medium snap-on will handle 5-6 turns.  Jim, 
> K9YC's tutorials are excellent.  Consult the Fair-Rite website for additional 
> technical data.
> 
> BTW, the Teflon dielectric allows easy soldering in PL-259s with RG-58 
> reducers without any fear of melting the dielectric.
> ---
> Chuck, AE4CW
> 
> -Original Message-
> From: Guy Olinger K2AV [mailto:k2av@gmail.com 
> <mailto:k2av@gmail.com>] 
> Sent: Sunday, February 07, 2016 01:08
> To: Robert Nobis <n7...@nobis.net <mailto:n7...@nobis.net>>
> Cc: elecraft@mailman.qth.net <mailto:elecraft@mailman.qth.net>; Ron D'Eau 
> Claire <r...@cobi.biz <mailto:r...@cobi.biz>>; Guy Olinger K2AV 
> <k2av@gmail.com <mailto:k2av@gmail.com>>
> Subject: Re: [Elecraft] Balun Questions
> 
> RG303 is not rated for the tight bends.  RG400 with its fine stranded center 
> conductor is rated for corner bends in aircraft wiring harnesses and will not 
> deform the dielectric within the bends. I would not wind any solid center 
> conductor coax on a toroid.
> 
> I would only buy cut lengths of RG400 after the lengths for a project are 
> known. Some number of such suppliers on eBay. One currently listed at 1.98 
> per foot:
> http://www.ebay.com/itm/RG400-Coaxial-Cable-Mil-spec-by-the-ft-US-supplier-/251260159394?hash=item3a8045c5a2:g:WpAAAOxy43FRafUe
>  
> <http://www.ebay.com/itm/RG400-Coaxial-Cable-Mil-spec-by-the-ft-US-supplier-/251260159394?hash=item3a8045c5a2:g:WpAAAOxy43FRafUe>
> 
> True it ain't ham cheep. The good stuff that lasts and lasts almost never is. 
> Back in the early days of eBay I came by a 142' length of RG400 for $25. 
> That's $0.178  a foot  I also came by bundles of miscellaneous 6 foot to 15 
> foot jumpers with various connectors on end for similar ridiculous low prices 
> per foot.
> 
> The silvered copper strands stand up to migration of dampness in a way not 
> possible with same size copper strands minus the silvering. I have
> *measured* the dry RF resistance at 1.83 MHz of a 67 foot length of corroded 
> #14 stranded plain copper at 62 ohms. When new this wire had resistance at RF 
> of less than an ohm. I have never found the silvered copper equivalent in 
> anything remotely approaching that degraded state.
> 
> RG400 wound on the proper core for the job will last a lifetime.
> 
> 73, Guy K2AV
> 
> On Saturday, February 6, 2016, Robert Nobis <n7...@nobis.net 
> <mailto:n7...@nobis.net>> wrote:
> 
> > I have used RG303/U for chokes.  A bit smaller diameter than RG400 
> > (0.170 versus 0.195 inches). RG303/U has a solid copper center 
> > conductor that is silver plated.  The shield for RG303 is also silver 
> > plated copper. The jacket is Class 9 Teflon. Also the dielectric material 
> > is teflon.
> >
> > 73,
> >
> >
> > Bob Nobis - N7RJN
> > n7...@nobis.net <mailto:n7...@nobis.net>
> >
> >
> > > On Feb 6, 2016, at 17:49, Guy Olinger K2AV <k2av@gmail.com 
> > > <mailto:k2av@gmail.com>> wrote:
> > >
> > > If one wants a small 50 ohm coax that will take QRO with a very 
> > > large margin and was *designed* for bending and use in aircraft 
> > > wiring
> > harnesses
> > > then use R

Re: [Elecraft] Balun Questions

[Mel Farrer via Elecraft]

SORRY, but the min static bending radius for RG-303 is 25 mm and RG-400 is 35 
mm.  For torroid wrap which is better?
Mel, K6KBE


  From: Chuck Catledge <ae...@att.net>
 To: 'Guy Olinger K2AV' <k2av@gmail.com>; 'Robert Nobis' <n7...@nobis.net> 
Cc: elecraft@mailman.qth.net; 'Ron D'Eau Claire' <r...@cobi.biz>
 Sent: Sunday, February 7, 2016 2:31 PM
 Subject: Re: [Elecraft] Balun Questions
   
At hamfests around the Southeast, surplus RG400 is often found in terminated 
cables (usually BNC or N) in lengths up to around 20 feet.  The price I've paid 
is always less than $1.00 per foot, sometimes much less.  I've used it to make 
dozens of RF chokes (1:1 baluns).  The small size of RG400 allows the use of a 
single medium to large clamp-on #31 ferrite that works effectively from 
10-160M, conditioned by the number of turns.  The large snap-on ferrite will 
accommodate 10-12 turns; the medium snap-on will handle 5-6 turns.  Jim, K9YC's 
tutorials are excellent.  Consult the Fair-Rite website for additional 
technical data.

BTW, the Teflon dielectric allows easy soldering in PL-259s with RG-58 reducers 
without any fear of melting the dielectric.
---
Chuck, AE4CW

-Original Message-
From: Guy Olinger K2AV [mailto:k2av@gmail.com] 
Sent: Sunday, February 07, 2016 01:08
To: Robert Nobis <n7...@nobis.net>
Cc: elecraft@mailman.qth.net; Ron D'Eau Claire <r...@cobi.biz>; Guy Olinger 
K2AV <k2av....@gmail.com>
Subject: Re: [Elecraft] Balun Questions

RG303 is not rated for the tight bends.  RG400 with its fine stranded center 
conductor is rated for corner bends in aircraft wiring harnesses and will not 
deform the dielectric within the bends. I would not wind any solid center 
conductor coax on a toroid.

I would only buy cut lengths of RG400 after the lengths for a project are 
known. Some number of such suppliers on eBay. One currently listed at 1.98 per 
foot:
http://www.ebay.com/itm/RG400-Coaxial-Cable-Mil-spec-by-the-ft-US-supplier-/251260159394?hash=item3a8045c5a2:g:WpAAAOxy43FRafUe

True it ain't ham cheep. The good stuff that lasts and lasts almost never is. 
Back in the early days of eBay I came by a 142' length of RG400 for $25. That's 
$0.178  a foot  I also came by bundles of miscellaneous 6 foot to 15 foot 
jumpers with various connectors on end for similar ridiculous low prices per 
foot.

The silvered copper strands stand up to migration of dampness in a way not 
possible with same size copper strands minus the silvering. I have
*measured* the dry RF resistance at 1.83 MHz of a 67 foot length of corroded 
#14 stranded plain copper at 62 ohms. When new this wire had resistance at RF 
of less than an ohm. I have never found the silvered copper equivalent in 
anything remotely approaching that degraded state.

RG400 wound on the proper core for the job will last a lifetime.

73, Guy K2AV

On Saturday, February 6, 2016, Robert Nobis <n7...@nobis.net> wrote:

> I have used RG303/U for chokes.  A bit smaller diameter than RG400 
> (0.170 versus 0.195 inches). RG303/U has a solid copper center 
> conductor that is silver plated.  The shield for RG303 is also silver 
> plated copper. The jacket is Class 9 Teflon. Also the dielectric material is 
> teflon.
>
> 73,
>
>
> Bob Nobis - N7RJN
> n7...@nobis.net
>
>
> > On Feb 6, 2016, at 17:49, Guy Olinger K2AV <k2av@gmail.com> wrote:
> >
> > If one wants a small 50 ohm coax that will take QRO with a very 
> > large margin and was *designed* for bending and use in aircraft 
> > wiring
> harnesses
> > then use RG400 to wind around your core. RG400 uses a fine stranded 
> > silvered copper center conductor that is more flexible than its 
> > Teflon dielectric. It has a double shield made from silvered copper strands.
> >
>
>
>


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Re: [Elecraft] Balun Questions

[Chuck Catledge]

It’s quite practical to use 25 to 35 mm radius bends of RG400 for large ferrite 
cores including both the one-piece and the snap-on varieties.  RG400 has the 
same diameter as RG-58, i.e. 0.195”.  See K9YC’s tutorial here:

http://audiosystemsgroup.com/RFI-Ham.pdf

 

All of the RF common mode chokes I have made using small cable (i.e. RG400 
through RG6) use radii of 1-3 inches with the RG6 tending toward 3” and greater 
due to the foam dielectric.  

---

Chuck, AE4CW

From: Mel Farrer [mailto:farrerfo...@yahoo.com] 
Sent: Sunday, February 07, 2016 17:54
To: Chuck Catledge <ae...@att.net>; 'Guy Olinger K2AV' <k2av@gmail.com>; 
'Robert Nobis' <n7...@nobis.net>
Cc: elecraft@mailman.qth.net; 'Ron D'Eau Claire' <r...@cobi.biz>
Subject: Re: [Elecraft] Balun Questions

 

SORRY, but the min static bending radius for RG-303 is 25 mm and RG-400 is 35 
mm.  For torroid wrap which is better?

 

Mel, K6KBE

 

  _  

From: Chuck Catledge <ae...@att.net <mailto:ae...@att.net> >
To: 'Guy Olinger K2AV' <k2av@gmail.com <mailto:k2av@gmail.com> >; 
'Robert Nobis' <n7...@nobis.net <mailto:n7...@nobis.net> > 
Cc: elecraft@mailman.qth.net <mailto:elecraft@mailman.qth.net> ; 'Ron D'Eau 
Claire' <r...@cobi.biz <mailto:r...@cobi.biz> >
Sent: Sunday, February 7, 2016 2:31 PM
Subject: Re: [Elecraft] Balun Questions


At hamfests around the Southeast, surplus RG400 is often found in terminated 
cables (usually BNC or N) in lengths up to around 20 feet.  The price I've paid 
is always less than $1.00 per foot, sometimes much less.  I've used it to make 
dozens of RF chokes (1:1 baluns).  The small size of RG400 allows the use of a 
single medium to large clamp-on #31 ferrite that works effectively from 
10-160M, conditioned by the number of turns.  The large snap-on ferrite will 
accommodate 10-12 turns; the medium snap-on will handle 5-6 turns.  Jim, K9YC's 
tutorials are excellent.  Consult the Fair-Rite website for additional 
technical data.

BTW, the Teflon dielectric allows easy soldering in PL-259s with RG-58 reducers 
without any fear of melting the dielectric.
---
Chuck, AE4CW

-Original Message-
From: Guy Olinger K2AV [mailto:k2av@gmail.com <mailto:k2av@gmail.com> ] 
Sent: Sunday, February 07, 2016 01:08
To: Robert Nobis <n7...@nobis.net <mailto:n7...@nobis.net> >
Cc: elecraft@mailman.qth.net <mailto:elecraft@mailman.qth.net> ; Ron D'Eau 
Claire <r...@cobi.biz <mailto:r...@cobi.biz> >; Guy Olinger K2AV 
<k2av@gmail.com <mailto:k2av@gmail.com> >
Subject: Re: [Elecraft] Balun Questions

RG303 is not rated for the tight bends.  RG400 with its fine stranded center 
conductor is rated for corner bends in aircraft wiring harnesses and will not 
deform the dielectric within the bends. I would not wind any solid center 
conductor coax on a toroid.

I would only buy cut lengths of RG400 after the lengths for a project are 
known. Some number of such suppliers on eBay. One currently listed at 1.98 per 
foot:
http://www.ebay.com/itm/RG400-Coaxial-Cable-Mil-spec-by-the-ft-US-supplier-/251260159394?hash=item3a8045c5a2:g:WpAAAOxy43FRafUe

True it ain't ham cheep. The good stuff that lasts and lasts almost never is. 
Back in the early days of eBay I came by a 142' length of RG400 for $25. That's 
$0.178  a foot  I also came by bundles of miscellaneous 6 foot to 15 foot 
jumpers with various connectors on end for similar ridiculous low prices per 
foot.

The silvered copper strands stand up to migration of dampness in a way not 
possible with same size copper strands minus the silvering. I have
*measured* the dry RF resistance at 1.83 MHz of a 67 foot length of corroded 
#14 stranded plain copper at 62 ohms. When new this wire had resistance at RF 
of less than an ohm. I have never found the silvered copper equivalent in 
anything remotely approaching that degraded state.

RG400 wound on the proper core for the job will last a lifetime.

73, Guy K2AV

On Saturday, February 6, 2016, Robert Nobis <n7...@nobis.net 
<mailto:n7...@nobis.net> > wrote:

> I have used RG303/U for chokes.  A bit smaller diameter than RG400 
> (0.170 versus 0.195 inches). RG303/U has a solid copper center 
> conductor that is silver plated.  The shield for RG303 is also silver 
> plated copper. The jacket is Class 9 Teflon. Also the dielectric material is 
> teflon.
>
> 73,
>
>
> Bob Nobis - N7RJN
> n7...@nobis.net <mailto:n7...@nobis.net> 
>
>
> > On Feb 6, 2016, at 17:49, Guy Olinger K2AV <k2av@gmail.com 
> > <mailto:k2av@gmail.com> > wrote:
> >
> > If one wants a small 50 ohm coax that will take QRO with a very 
> > large margin and was *designed* for bending and use in aircraft 
> > wiring
> harnesses
> > then use RG400 to wind around your core. RG400 uses a fine str

Re: [Elecraft] Balun Questions

[Bob McGraw K4TAX]

I am speaking of the radius of the coax bend.   To have a coax bend 
radius of 3" the torroid would be huge...the size of a large coffee 
can.  A 3" OD, x 1.5" ID   torroid would typically have a winding radius 
of less than ~1", even with 2 stacked cores.For my "ugly balun" 
project I use 4" ID PVC which has an OD of ~4.5" and which provides a 
bend radius of 2.25".


73
Bob, K4TAX



On 2/7/2016 10:32 PM, Chuck Catledge wrote:

It’s quite practical to use 25 to 35 mm radius bends of RG400 for large ferrite 
cores including both the one-piece and the snap-on varieties.  RG400 has the 
same diameter as RG-58, i.e. 0.195”.  See K9YC’s tutorial here:

http://audiosystemsgroup.com/RFI-Ham.pdf

All of the RF common mode chokes I have made using small cable (i.e. RG400 
through RG6) use radii of 1-3 inches with the RG6 tending toward 3” and greater 
due to the foam dielectric.

---

Chuck, AE4CW

From: Mel Farrer [mailto:farrerfo...@yahoo.com]

Subject: Re: [Elecraft] Balun Questions

  


SORRY, but the min static bending radius for RG-303 is 25 mm and RG-400 is 35 
mm.  For torroid wrap which is better?





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Re: [Elecraft] Balun Questions

[Bill Frantz]

I just completed a 160/80M common mode choke made from 6 type 31 
cores. Each core is 1/2" inside diameter, 1" outside diameter, 
and 1" long. (12.5mm, 25mm, 25mm). There are four windings of 
RG58 and I think this design is in agreements with Jim Brown, 
K9YC's RFI-ham.pdf. The choke hangs just below the feed point of 
my 160M dipole/80M inverted V. The antennas are at 44' (12M). 
The choke appears to work well and seems to have knocked the 
noise levels on 160M down an S unit or two. I was able to hear 
and work DX during the CQ contest further away than before.


The cores are separated by about an inch each and the total 
diameter of the windings is about 8 inches (200mm). I don't 
think you need to wrap tightly to the cores.


I have no test information, lacking equipment.

73 Bill AE6JV

On 2/7/16 at 9:03 PM, rmcg...@blomand.net (Bob McGraw K4TAX) wrote:

I am speaking of the radius of the coax bend.   To have a coax 
bend radius of 3" the torroid would be huge...the size of a 
large coffee can.  A 3" OD, x 1.5" ID   torroid would typically 
have a winding radius of less than ~1", even with 2 stacked 
cores.For my "ugly balun" project I use 4" ID PVC which has 
an OD of ~4.5" and which provides a bend radius of 2.25".


---
Bill Frantz| "The only thing we have to   | Periwinkle
(408)356-8506  | fear is fear itself." - FDR  | 16345 
Englewood Ave
www.pwpconsult.com | Inaugural address, 3/4/1933  | Los Gatos, 
CA 95032


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Re: [Elecraft] Balun Questions

[Jim Allen]

Almost all of G3TXQ's tests on his website with ferrite core baluns involved 
RG58, so I figured RG8X would be even better.  I have a lot of it, and no RG58.

Luckily, these things are easy to work with, so if I ever have/want/need to 
change it, it's so easy even a lawyer can do it, 3 out of 5 tries, anyway.

I see also that Steve's test methods involve equipment I don't have or ever 
heard of!

Thanks for the inputs, men, and the off list e-mails, too.  At least I won't be 
as dumb for the rest of my life as I was last week.

73 de W6OGC Jim Allen 

Sent from my iPad
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Re: [Elecraft] Balun Questions

[Ron D'Eau Claire]

Bob makes an excellent point. I've seen cases where even "solid" dielectric
did that over time because, after all, it is not really solid. The
dielectric is plastic so the coax can be bent. 

All coax has a minimum bending radius specification. Specific data is
available on line but, in general, RG58 size cable usually has a minimum
radius of 1 to 1.5 inches (2.5 to 3.8 cm) and RG8 size cable has a minimum
radius of at least 2 inches (5 cm). Note that is radius. If you curl the
cable into a circle the minimum diameter of that circle should be at least
twice that or 3 to 4 inches (7.5 to 10 cm). 

It's not something I've found especially critical in HF applications at
least around my shack, but tighter bends, which may not actually cause a
short (yet), alter the impedance as the center conductor migrates toward one
side so it is no longer equally spaced within the shield. This can be a
serious issue in microwave and even UHF installations. 

73, Ron AC7AC



-Original Message-
I would have concern that long term usage of RG-8X, being foam core
dielectric material and bent in a tight radius, may allow the center
conductor to migrate to the inside radius of the bend.  The Minimum Bend 
Radius for RG-8X is 2.50". Thus the tight bend will allow the center 
conductor to short to the shield.  A solid core dielectric coax such as
RG-303  is much preferred.

73
Bob, K4TAX


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Re: [Elecraft] Balun Questions

[Dave Olean]

Tell me about it! I made a 1/2 wave balun for a 432 yagi. I used Times FM-8 
foam coax. (RG-8 sized with low loss foam dielectric) and it was bent in a U 
shape that did not exceed the bending radius.  I tested it with a 700 watt 
output amplifier and the VSWR went through the roof in under a second. The 
coax center conductor drifted away from the center at the midway point of 
the balun and caused the high VSWR. It did not short out, but was rendered 
unuseable. I ended up making a 1/4 wave balun with copper pipe and a Delta 
match. Don't use foam coax for high voltage either!


Dave K1WHS
- Original Message - 
From: "Ron D'Eau Claire" <r...@cobi.biz>

To: <elecraft@mailman.qth.net>
Sent: Saturday, February 06, 2016 10:33 PM
Subject: Re: [Elecraft] Balun Questions


Bob makes an excellent point. I've seen cases where even "solid" 
dielectric

did that over time because, after all, it is not really solid. The
dielectric is plastic so the coax can be bent.

All coax has a minimum bending radius specification. Specific data is
available on line but, in general, RG58 size cable usually has a minimum
radius of 1 to 1.5 inches (2.5 to 3.8 cm) and RG8 size cable has a minimum
radius of at least 2 inches (5 cm). Note that is radius. If you curl the
cable into a circle the minimum diameter of that circle should be at least
twice that or 3 to 4 inches (7.5 to 10 cm).

It's not something I've found especially critical in HF applications at
least around my shack, but tighter bends, which may not actually cause a
short (yet), alter the impedance as the center conductor migrates toward 
one

side so it is no longer equally spaced within the shield. This can be a
serious issue in microwave and even UHF installations.

73, Ron AC7AC



-Original Message-
I would have concern that long term usage of RG-8X, being foam core
dielectric material and bent in a tight radius, may allow the center
conductor to migrate to the inside radius of the bend.  The Minimum Bend
Radius for RG-8X is 2.50". Thus the tight bend will allow the center
conductor to short to the shield.  A solid core dielectric coax such as
RG-303  is much preferred.

73
Bob, K4TAX


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Re: [Elecraft] Balun Questions

[Guy Olinger K2AV]

If one wants a small 50 ohm coax that will take QRO with a very large
margin and was *designed* for bending and use in aircraft wiring harnesses
then use RG400 to wind around your core. RG400 uses a fine stranded
silvered copper center conductor that is more flexible than its Teflon
dielectric. It has a double shield made from silvered copper strands.

That's silvered strands whose silver sulphide patina or tarnish is
conductive as opposed to the green copper sulphate that separates copper
strands that have been water soaked.

Wind the coil form with RG59 to get the length and buy just what RG400 you
need. You can buy brand new RG400 by the foot.  With the Teflon dielectric
you can solder the RG400 without worrying about melting it.

Do it with the good stuff to start with and put it in your will.

73, Guy K2AV

On Saturday, February 6, 2016, Ron D'Eau Claire  wrote:

> Bob makes an excellent point. I've seen cases where even "solid" dielectric
> did that over time because, after all, it is not really solid. The
> dielectric is plastic so the coax can be bent.
>
> All coax has a minimum bending radius specification. Specific data is
> available on line but, in general, RG58 size cable usually has a minimum
> radius of 1 to 1.5 inches (2.5 to 3.8 cm) and RG8 size cable has a minimum
> radius of at least 2 inches (5 cm). Note that is radius. If you curl the
> cable into a circle the minimum diameter of that circle should be at least
> twice that or 3 to 4 inches (7.5 to 10 cm).
>
> It's not something I've found especially critical in HF applications at
> least around my shack, but tighter bends, which may not actually cause a
> short (yet), alter the impedance as the center conductor migrates toward
> one
> side so it is no longer equally spaced within the shield. This can be a
> serious issue in microwave and even UHF installations.
>
> 73, Ron AC7AC
>
>
>
> -Original Message-
> I would have concern that long term usage of RG-8X, being foam core
> dielectric material and bent in a tight radius, may allow the center
> conductor to migrate to the inside radius of the bend.  The Minimum Bend
> Radius for RG-8X is 2.50". Thus the tight bend will allow the center
> conductor to short to the shield.  A solid core dielectric coax such as
> RG-303  is much preferred.
>
> 73
> Bob, K4TAX
>
>
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>


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Re: [Elecraft] Balun Questions

[Guy Olinger K2AV]

On Saturday, February 6, 2016, Jim Allen  wrote:

>  I used RG8X coax, a 2.4" core, not sure exactly what mix, and 11 turns.
>

There is a *huge* variation in core materials and performance specifics found
in the FT241 form factor.

It really matters what the actual material is. On 160 the variation in the
balun could be performance anywhere between fairly decent
and amazingly pathetic.

73, Guy K2AV

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Re: [Elecraft] Balun Questions

[Jim Allen]

Ok, so this morning, I went out to the shack and whipped up a balun, from a 
G3TXQ design I found on the website of W5DXP.com.  It is coax wrapped around a 
ferrite core, with appropriate connectors in a plastic weathertight box.  I 
used RG8X coax, a 2.4" core, not sure exactly what mix, and 11 turns.

How do I test this device to get its properties, impedance at various 
frequencies, etc?  

It appears to function when I put it inline.  The KAT100 seems happy.  It 
produces a decent match on 40-10m using the 44' long rotating dipole at ~37' 
fed with 450 ohm twin lead.  I have no idea how efficient it might be, of 
course, if at all.

I still don't hear the VP8 much above the noise. :>(

73 de W6OGC Jim Allen 

Sent from my iPad
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Re: [Elecraft] Balun Questions

[Wes (N7WS)]

If you're driving a 50 ohm load, then the cable wound around the core is just an 
extension of the transmission line and has no impedance modifying effects.


The significant parameter is the common mode (CM) impedance. G3TXQ discusses a 
way to measure it here: http://www.karinya.net/g3txq/chokes/#measurement


You can back into whether the CM is high enough by terminating each output with 
a resistive load to ground and measuring the two output voltages and phases with 
something like an HP8405 Vector Voltmeter.  Walt Maxwell, W2DU, discussed this 
in his book, "Reflections II" (p, 21-8 thru 21-10)


On 2/6/2016 11:06 AM, Jim Allen wrote:

Ok, so this morning, I went out to the shack and whipped up a balun, from a G3TXQ 
design I found on the website of W5DXP.com.  It is coax wrapped around a ferrite 
core, with appropriate connectors in a plastic weathertight box.  I used RG8X coax, 
a 2.4" core, not sure exactly what mix, and 11 turns.

How do I test this device to get its properties, impedance at various 
frequencies, etc?

It appears to function when I put it inline.  The KAT100 seems happy.  It 
produces a decent match on 40-10m using the 44' long rotating dipole at ~37' 
fed with 450 ohm twin lead.  I have no idea how efficient it might be, of 
course, if at all.

I still don't hear the VP8 much above the noise. :>(

73 de W6OGC Jim Allen

Sent from my iPad
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Re: [Elecraft] Balun Questions

[Bob McGraw K4TAX]

I would have concern that long term usage of RG-8X, being foam core 
dielectric material and bent in a tight radius, may allow the center 
conductor to migrate to the inside radius of the bend.  The Minimum Bend 
Radius for RG-8X is 2.50". Thus the tight bend will allow the center 
conductor to short to the shield.  A solid core dielectric coax such as 
RG-303  is much preferred.


73
Bob, K4TAX



On 2/6/2016 1:22 PM, Guy Olinger K2AV wrote:

On Saturday, February 6, 2016, Jim Allen  wrote:


  I used RG8X coax, a 2.4" core, not sure exactly what mix, and 11 turns.


There is a *huge* variation in core materials and performance specifics found
in the FT241 form factor.

It really matters what the actual material is. On 160 the variation in the
balun could be performance anywhere between fairly decent
and amazingly pathetic.

73, Guy K2AV




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Re: [Elecraft] Balun Questions

[Bob McGraw K4TAX]

Yep, good stuff.  Be sure of your budget before buying a roll.  It is a 
bit pricey.  Handles legal limit HF power with a reasonable SWR.


73
Bob, K4TAX



On 2/6/2016 7:10 PM, Robert Nobis wrote:

I have used RG303/U for chokes.  A bit smaller diameter than RG400 (0.170 
versus 0.195 inches). RG303/U has a solid copper center conductor that is 
silver plated.  The shield for RG303 is also silver plated copper. The jacket 
is Class 9 Teflon. Also the dielectric material is teflon.

73,


Bob Nobis - N7RJN
n7...@nobis.net



On Feb 6, 2016, at 17:49, Guy Olinger K2AV  wrote:

If one wants a small 50 ohm coax that will take QRO with a very large
margin and was *designed* for bending and use in aircraft wiring harnesses
then use RG400 to wind around your core. RG400 uses a fine stranded
silvered copper center conductor that is more flexible than its Teflon
dielectric. It has a double shield made from silvered copper strands.

That's silvered strands whose silver sulphide patina or tarnish is
conductive as opposed to the green copper sulphate that separates copper
strands that have been water soaked.

Wind the coil form with RG59 to get the length and buy just what RG400 you
need. You can buy brand new RG400 by the foot.  With the Teflon dielectric
you can solder the RG400 without worrying about melting it.

Do it with the good stuff to start with and put it in your will.

73, Guy K2AV

On Saturday, February 6, 2016, Ron D'Eau Claire  wrote:


Bob makes an excellent point. I've seen cases where even "solid" dielectric
did that over time because, after all, it is not really solid. The
dielectric is plastic so the coax can be bent.

All coax has a minimum bending radius specification. Specific data is
available on line but, in general, RG58 size cable usually has a minimum
radius of 1 to 1.5 inches (2.5 to 3.8 cm) and RG8 size cable has a minimum
radius of at least 2 inches (5 cm). Note that is radius. If you curl the
cable into a circle the minimum diameter of that circle should be at least
twice that or 3 to 4 inches (7.5 to 10 cm).

It's not something I've found especially critical in HF applications at
least around my shack, but tighter bends, which may not actually cause a
short (yet), alter the impedance as the center conductor migrates toward
one
side so it is no longer equally spaced within the shield. This can be a
serious issue in microwave and even UHF installations.

73, Ron AC7AC



-Original Message-
I would have concern that long term usage of RG-8X, being foam core
dielectric material and bent in a tight radius, may allow the center
conductor to migrate to the inside radius of the bend.  The Minimum Bend
Radius for RG-8X is 2.50". Thus the tight bend will allow the center
conductor to short to the shield.  A solid core dielectric coax such as
RG-303  is much preferred.

73
Bob, K4TAX


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Re: [Elecraft] Balun Questions

[Wes (N7WS)]

I can second Jim's concern about have one's work usurped by another.  I can 
recall Googling a topic and having a paper come up on some Canadian's website 
that appeared to be written by him but in fact was my ladderline paper.  I 
emailed him and asked him nicely to remove it and simply link to my site. He 
refused to do so, so I contacted his ISP and made them aware that he was 
violating their TOS.  I guess he gave them a ration of crap so they closed his 
account.


Bill Orr had my noise blanker circuit in his Handbook for years without me even 
knowing about it until a friend mentioned it.  Of course, Ham Radio Magazine 
held copyright and I suppose gave him permission but it would have been nice to 
know.  It would have been even nicer to have received a copy.


Another example: A good friend of mine who is a stunning photographer 
https://www.flickr.com/photos/gauchocat/ had someone tell him, "Hey Glenn, I saw 
your photo in Audubon Magazine."  You guessed it, downloaded from Flickr.


Jim does excellent work; he should get credit for it.


On 2/6/2016 10:35 PM, Jim Brown wrote:

On Sat,2/6/2016 4:33 PM, Jim Allen wrote:
Almost all of G3TXQ's tests on his website with ferrite core baluns involved 
RG58, so I figured RG8X would be even better.  I have a lot of it, and no RG58.


Did you study the material on my website? My measurement method is clearly 
described in several of the publications, including the RFI tutorial, the AES 
Paper, and the Power Point for talks I've done for several ham clubs and 
conventions. The equipment consists of an HP Generator and HP Spectrum 
Analyzer (which was used as a terminated RF voltmeter).


My work, and its publication precedes G3TXQ's by at least five years. His work 
is clearly inspired by mine (and I would think by W1HIS's), yet he fails to 
credit either of us. All of my writing credits others who have made important 
contributions on the topic I'm writing about. I did, for example, reference 
work and texts by Henry Ott, Clayton Paul, W1HIS, E. C. Snelling, Neil Muncy, 
Bill Whitlock, Jerry Sevick, and Doug DeMaw in the RFI tutorial.


The "Cookbook" that is part of my RFI tutorial is based directly on the 
measured data that is discussed throughout the tutorial and summarized in 
Appendix One.


73, Jim K9YC
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Re: [Elecraft] Balun Questions

[Robert Nobis]

Guy,

After reviewing specs from several manufacturers, the “recommended” minimum 
bend radius for RG303 and RG400 is essentially the same at 1.0 inches.  

73,



Bob Nobis - N7RJN
n7...@nobis.net


> On Feb 6, 2016, at 23:07, Guy Olinger K2AV  wrote:
> 
> RG303 is not rated for the tight bends.  RG400 with its fine stranded center 
> conductor is rated for corner bends in aircraft wiring harnesses and will not 
> deform the dielectric within the bends. I would not wind any solid center 
> conductor coax on a toroid. 
> 
> I would only buy cut lengths of RG400 after the lengths for a project are 
> known. Some number of such suppliers on eBay. One currently listed at 1.98 
> per foot: 
> http://www.ebay.com/itm/RG400-Coaxial-Cable-Mil-spec-by-the-ft-US-supplier-/251260159394?hash=item3a8045c5a2:g:WpAAAOxy43FRafUe
>  
> 
> 
> True it ain't ham cheep. The good stuff that lasts and lasts almost never is. 
> Back in the early days of eBay I came by a 142' length of RG400 for $25. 
> That's $0.178  a foot  I also came by bundles of miscellaneous 6 foot to 15 
> foot jumpers with various connectors on end for similar ridiculous low prices 
> per foot. 
> 
> The silvered copper strands stand up to migration of dampness in a way not 
> possible with same size copper strands minus the silvering. I have *measured* 
> the dry RF resistance at 1.83 MHz of a 67 foot length of corroded #14 
> stranded plain copper at 62 ohms. When new this wire had resistance at RF of 
> less than an ohm. I have never found the silvered copper equivalent in 
> anything remotely approaching that degraded state.
> 
> RG400 wound on the proper core for the job will last a lifetime.
> 
> 73, Guy K2AV 
> 
> On Saturday, February 6, 2016, Robert Nobis > wrote:
> I have used RG303/U for chokes.  A bit smaller diameter than RG400 (0.170 
> versus 0.195 inches). RG303/U has a solid copper center conductor that is 
> silver plated.  The shield for RG303 is also silver plated copper. The jacket 
> is Class 9 Teflon. Also the dielectric material is teflon.
> 
> 73,
> 
> 
> Bob Nobis - N7RJN
> n7...@nobis.net <>
> 
> 
> > On Feb 6, 2016, at 17:49, Guy Olinger K2AV > wrote:
> >
> > If one wants a small 50 ohm coax that will take QRO with a very large
> > margin and was *designed* for bending and use in aircraft wiring harnesses
> > then use RG400 to wind around your core. RG400 uses a fine stranded
> > silvered copper center conductor that is more flexible than its Teflon
> > dielectric. It has a double shield made from silvered copper strands.
> >
> 
> 

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Re: [Elecraft] Balun Questions

[Robert Nobis]

Bob,

Yes, it is a bit expensive: $2.91 per foot from “The Wireman” plus shipping.  
(For lengths under 100 feet.)

73,


Bob Nobis - N7RJN
n7...@nobis.net


> On Feb 6, 2016, at 18:21, Bob McGraw K4TAX  wrote:
> 
> Yep, good stuff.  Be sure of your budget before buying a roll.  It is a bit 
> pricey.  Handles legal limit HF power with a reasonable SWR.
> 
> 73
> Bob, K4TAX
> 
> 
> 
> On 2/6/2016 7:10 PM, Robert Nobis wrote:
>> I have used RG303/U for chokes.  A bit smaller diameter than RG400 (0.170 
>> versus 0.195 inches). RG303/U has a solid copper center conductor that is 
>> silver plated.  The shield for RG303 is also silver plated copper. The 
>> jacket is Class 9 Teflon. Also the dielectric material is teflon.
>> 
>> 73,
>> 
>> 
>> Bob Nobis - N7RJN
>> n7...@nobis.net
>> 
>> 
>>> On Feb 6, 2016, at 17:49, Guy Olinger K2AV  wrote:
>>> 
>>> If one wants a small 50 ohm coax that will take QRO with a very large
>>> margin and was *designed* for bending and use in aircraft wiring harnesses
>>> then use RG400 to wind around your core. RG400 uses a fine stranded
>>> silvered copper center conductor that is more flexible than its Teflon
>>> dielectric. It has a double shield made from silvered copper strands.
>>> 
>>> That's silvered strands whose silver sulphide patina or tarnish is
>>> conductive as opposed to the green copper sulphate that separates copper
>>> strands that have been water soaked.
>>> 
>>> Wind the coil form with RG59 to get the length and buy just what RG400 you
>>> need. You can buy brand new RG400 by the foot.  With the Teflon dielectric
>>> you can solder the RG400 without worrying about melting it.
>>> 
>>> Do it with the good stuff to start with and put it in your will.
>>> 
>>> 73, Guy K2AV
>>> 
>>> On Saturday, February 6, 2016, Ron D'Eau Claire  wrote:
>>> 
 Bob makes an excellent point. I've seen cases where even "solid" dielectric
 did that over time because, after all, it is not really solid. The
 dielectric is plastic so the coax can be bent.
 
 All coax has a minimum bending radius specification. Specific data is
 available on line but, in general, RG58 size cable usually has a minimum
 radius of 1 to 1.5 inches (2.5 to 3.8 cm) and RG8 size cable has a minimum
 radius of at least 2 inches (5 cm). Note that is radius. If you curl the
 cable into a circle the minimum diameter of that circle should be at least
 twice that or 3 to 4 inches (7.5 to 10 cm).
 
 It's not something I've found especially critical in HF applications at
 least around my shack, but tighter bends, which may not actually cause a
 short (yet), alter the impedance as the center conductor migrates toward
 one
 side so it is no longer equally spaced within the shield. This can be a
 serious issue in microwave and even UHF installations.
 
 73, Ron AC7AC
 
 
 
 -Original Message-
 I would have concern that long term usage of RG-8X, being foam core
 dielectric material and bent in a tight radius, may allow the center
 conductor to migrate to the inside radius of the bend.  The Minimum Bend
 Radius for RG-8X is 2.50". Thus the tight bend will allow the center
 conductor to short to the shield.  A solid core dielectric coax such as
 RG-303  is much preferred.
 
 73
 Bob, K4TAX
 
 
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 Message delivered to k2av@gmail.com 
 
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Re: [Elecraft] Balun Questions

[Ron D'Eau Claire]

A favorite of mine for transmission line transformers or common-mode chokes 
(a.k.a. "baluns") is to use a twisted pair instead of coax. Cheap and effective 
and with a little calculation you can approximate any impedance line you want. 

K2 builders know this technique from winding T6 in their rigs. 

73, Ron AC7AC

-Original Message-
 I would have concern that long term usage of RG-8X, being foam core 
 dielectric material and bent in a tight radius, may allow the 
 center conductor to migrate to the inside radius of the bend.  The Minimum 
 Bend
 Radius for RG-8X is 2.50". Thus the tight bend will allow the center
 conductor to short to the shield.  A solid core dielectric coax 
 such as
 RG-303  is much preferred.
 
 73
 Bob, K4TAX

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Re: [Elecraft] Balun Questions

[Robert Nobis]

I have used RG303/U for chokes.  A bit smaller diameter than RG400 (0.170 
versus 0.195 inches). RG303/U has a solid copper center conductor that is 
silver plated.  The shield for RG303 is also silver plated copper. The jacket 
is Class 9 Teflon. Also the dielectric material is teflon.

73,


Bob Nobis - N7RJN
n7...@nobis.net


> On Feb 6, 2016, at 17:49, Guy Olinger K2AV  wrote:
> 
> If one wants a small 50 ohm coax that will take QRO with a very large
> margin and was *designed* for bending and use in aircraft wiring harnesses
> then use RG400 to wind around your core. RG400 uses a fine stranded
> silvered copper center conductor that is more flexible than its Teflon
> dielectric. It has a double shield made from silvered copper strands.
> 
> That's silvered strands whose silver sulphide patina or tarnish is
> conductive as opposed to the green copper sulphate that separates copper
> strands that have been water soaked.
> 
> Wind the coil form with RG59 to get the length and buy just what RG400 you
> need. You can buy brand new RG400 by the foot.  With the Teflon dielectric
> you can solder the RG400 without worrying about melting it.
> 
> Do it with the good stuff to start with and put it in your will.
> 
> 73, Guy K2AV
> 
> On Saturday, February 6, 2016, Ron D'Eau Claire  wrote:
> 
>> Bob makes an excellent point. I've seen cases where even "solid" dielectric
>> did that over time because, after all, it is not really solid. The
>> dielectric is plastic so the coax can be bent.
>> 
>> All coax has a minimum bending radius specification. Specific data is
>> available on line but, in general, RG58 size cable usually has a minimum
>> radius of 1 to 1.5 inches (2.5 to 3.8 cm) and RG8 size cable has a minimum
>> radius of at least 2 inches (5 cm). Note that is radius. If you curl the
>> cable into a circle the minimum diameter of that circle should be at least
>> twice that or 3 to 4 inches (7.5 to 10 cm).
>> 
>> It's not something I've found especially critical in HF applications at
>> least around my shack, but tighter bends, which may not actually cause a
>> short (yet), alter the impedance as the center conductor migrates toward
>> one
>> side so it is no longer equally spaced within the shield. This can be a
>> serious issue in microwave and even UHF installations.
>> 
>> 73, Ron AC7AC
>> 
>> 
>> 
>> -Original Message-
>> I would have concern that long term usage of RG-8X, being foam core
>> dielectric material and bent in a tight radius, may allow the center
>> conductor to migrate to the inside radius of the bend.  The Minimum Bend
>> Radius for RG-8X is 2.50". Thus the tight bend will allow the center
>> conductor to short to the shield.  A solid core dielectric coax such as
>> RG-303  is much preferred.
>> 
>> 73
>> Bob, K4TAX
>> 
>> 
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Re: [Elecraft] Balun Questions

[Guy Olinger K2AV]

RG303 is not rated for the tight bends.  RG400 with its fine stranded
center conductor is rated for corner bends in aircraft wiring harnesses and
will not deform the dielectric within the bends. I would not wind any solid
center conductor coax on a toroid.

I would only buy cut lengths of RG400 after the lengths for a project are
known. Some number of such suppliers on eBay. One currently listed at 1.98
per foot:
http://www.ebay.com/itm/RG400-Coaxial-Cable-Mil-spec-by-the-ft-US-supplier-/251260159394?hash=item3a8045c5a2:g:WpAAAOxy43FRafUe

True it ain't ham cheep. The good stuff that lasts and lasts almost never
is. Back in the early days of eBay I came by a 142' length of RG400 for
$25. That's $0.178  a foot  I also came by bundles of miscellaneous 6 foot
to 15 foot jumpers with various connectors on end for similar ridiculous
low prices per foot.

The silvered copper strands stand up to migration of dampness in a way not
possible with same size copper strands minus the silvering. I have
*measured* the dry RF resistance at 1.83 MHz of a 67 foot length of
corroded #14 stranded plain copper at 62 ohms. When new this wire had
resistance at RF of less than an ohm. I have never found the silvered
copper equivalent in anything remotely approaching that degraded state.

RG400 wound on the proper core for the job will last a lifetime.

73, Guy K2AV

On Saturday, February 6, 2016, Robert Nobis  wrote:

> I have used RG303/U for chokes.  A bit smaller diameter than RG400 (0.170
> versus 0.195 inches). RG303/U has a solid copper center conductor that is
> silver plated.  The shield for RG303 is also silver plated copper. The
> jacket is Class 9 Teflon. Also the dielectric material is teflon.
>
> 73,
>
>
> Bob Nobis - N7RJN
> n7...@nobis.net
>
>
> > On Feb 6, 2016, at 17:49, Guy Olinger K2AV  wrote:
> >
> > If one wants a small 50 ohm coax that will take QRO with a very large
> > margin and was *designed* for bending and use in aircraft wiring
> harnesses
> > then use RG400 to wind around your core. RG400 uses a fine stranded
> > silvered copper center conductor that is more flexible than its Teflon
> > dielectric. It has a double shield made from silvered copper strands.
> >
>
>
>
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Re: [Elecraft] Balun Questions

[Vic Rosenthal]

Wow, that is eye opening! I always thought I was just lazy/cheap when I merely 
polished my amplifier tank coils and sprayed them with clear plastic (Krylon), 
but it seems I was doing the right thing after all.

Vic 4X6GP/K2VCO

> On 7 Feb 2016, at 3:48 AM, Wes (N7WS)  wrote:
> 
> On oft repeated myth.
> 
> See: http://k6mhe.com/n7ws/Plating.pdf
> 
> 
>> On 2/6/2016 5:49 PM, Guy Olinger K2AV wrote:
>> 
>> That's silvered strands whose silver sulphide patina or tarnish is
>> conductive as opposed to the green copper sulphate that separates copper
>> strands that have been water soaked.
> 
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Re: [Elecraft] Balun Questions

[Jim Brown]

On Sat,2/6/2016 4:33 PM, Jim Allen wrote:

Almost all of G3TXQ's tests on his website with ferrite core baluns involved 
RG58, so I figured RG8X would be even better.  I have a lot of it, and no RG58.


Did you study the material on my website? My measurement method is 
clearly described in several of the publications, including the RFI 
tutorial, the AES Paper, and the Power Point for talks I've done for 
several ham clubs and conventions. The equipment consists of an HP 
Generator and HP Spectrum Analyzer (which was used as a terminated RF 
voltmeter).


My work, and its publication precedes G3TXQ's by at least five years. 
His work is clearly inspired by mine (and I would think by W1HIS's), yet 
he fails to credit either of us. All of my writing credits others who 
have made important contributions on the topic I'm writing about. I did, 
for example, reference work and texts by Henry Ott, Clayton Paul, W1HIS, 
E. C. Snelling, Neil Muncy, Bill Whitlock, Jerry Sevick, and Doug DeMaw 
in the RFI tutorial.


The "Cookbook" that is part of my RFI tutorial is based directly on the 
measured data that is discussed throughout the tutorial and summarized 
in Appendix One.


73, Jim K9YC
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Re: [Elecraft] Balun Questions

[Wes (N7WS)]

On oft repeated myth.

See: http://k6mhe.com/n7ws/Plating.pdf


On 2/6/2016 5:49 PM, Guy Olinger K2AV wrote:


That's silvered strands whose silver sulphide patina or tarnish is
conductive as opposed to the green copper sulphate that separates copper
strands that have been water soaked.




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Re: [Elecraft] Balun suggestions

[Jim Brown]

On Fri,2/5/2016 5:06 AM, w7aqk wrote:
I don't know what the precise definition for "balanced" will end up 
being (assuming we end up with a consensus),


The laws of physics are not determined by consensus. I am citing the 
definition upon which IEC and AES Standards are based, which are 
established by international bodies of first rate engineers. I'm a 
member of the AES Standards Committee. It may come as a shock to some, 
but almost everything fundamental about electricity, electronics, audio, 
radio, and transmission lines was well understood and documented nearly 
100 years ago, and much of it decades earlier.


There's a slide presentation on RFI on my website that addresses the 
topic of balance. GM3SEK and N7WS clearly understand it.


73, Jim K9YC
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Re: [Elecraft] Balun suggestions

[Wes (N7WS)]

Correct on all points.

On 2/5/2016 6:06 AM, w7aqk wrote:

Jim B. and All,

I don't know what the precise definition for "balanced" will end up being 
(assuming we end up with a consensus), but In Jim B's critique about what was 
said, I think he cut and pasted so as to erroneously attribute comments made 
by Don, W3FPR, as being made by Wes N7WS.  It's getting hard to keep track of 
who said what! Hi.  Interesting debate, however.


Dave W7AQK



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Re: [Elecraft] Balun suggestions

[CUTTER DAVID]

DJ0IP must be one of, if not the post prolific testers of baluns and chokes
*attached to aerials* ever.  He does not measure them in the lab.  His
measurements are practical and done with rigour using modest equipment.  He has
done thousands of measurements for common mode current, only a fraction of which
are on his website.   Some of his results are not complimentary to commercial
balun manufacturers.  Caveat emptor.  I'm glad his work is beginning to be
recognised.

David, G3UNA

> 
> On 04 February 2016 at 23:10 Bob McGraw K4TAX  wrote:
> 
> 
> As one that has personally used a balanced fed antennas for years, I
> suggest you review the info on this site.
> http://www.dj0ip.de/balun-stuff/ 
> 
> Good stuff on evaluating or building a proper balun.
> 
> And for open wire fed antennas:
> http://www.dj0ip.de/open-wire-fed-ant/
> 
> To answer your question, a high power 1:1 current balun is likely best.
> Of course you could built a balanced tuner as I did. Problem solved.
> That's another story.
> 
> Keep in mind that balun power ratings are for "matched" conditions.
> Which in fact is never the case with a center fed wire and open wire or
> a balanced feed line. At a mighty 5 watts it would not be of concern.
> 
> If at all possible, run the balanced feed line from the antenna feed
> point all the way to the operating position. Keep the coax run between
> the tuner output and balun input as short as practical. After all, the
> reason to use balanced feed line is to take advantage of the low loss
> properties.
> 
> Never fear, the use of balanced feed line is not near as critical or
> fussy as the "masses" will so tout. Many hams express fear in using
> balanced feed systems, largely because of what they have heard. Mostly
> because it frankly isn't fact. Mine feeds a 256 ft center fed wire and
> comes down the tower supported on home made 9" PVC stand-offs, through
> the attic eve vent, across the roof rafters, and drops down through the
> ceiling to the tuner on the shelf above the desk. Not bad for a 160M -
> 10M antenna. {see my pix on QRZ.COM that shows a bit of the line
> going up the wall.}
> 
> 73
> Bob, K4TAX
> 
> 
> 
> On 2/4/2016 2:55 PM, Jim Allen wrote:
> > K2/100 and KAT100 here.
> >
> > I am changing around my modest antenna configuration now. I have been
> > using the K2/100 with my AH-4, and now wish to use the KAT100 with
> > balanced feedline antennas.
> >
> > What balun, homebrew or commercial, if any, should I use? I almost
> > always run 5 watts, all CW.
> >
> > 73 de W6OGC Jim Allen
> >
> > Sent from my iPad
> > __
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> > Message delivered to rmcg...@blomand.net
> >
> 
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Re: [Elecraft] Balun suggestions

[w7aqk]

Jim B. and All,

I don't know what the precise definition for "balanced" will end up being 
(assuming we end up with a consensus), but In Jim B's critique about what 
was said, I think he cut and pasted so as to erroneously attribute comments 
made by Don, W3FPR, as being made by Wes N7WS.  It's getting hard to keep 
track of who said what!  Hi.  Interesting debate, however.


Dave W7AQK


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Re: [Elecraft] Balun suggestions

[Ian White]

Wes's point is that twin feeder is not automatically "balanced" - very far
from it! Twin feeder happily supports both differential (equal and opposite,
balanced) currents and common-mode current at the same time.

So, in the real world, there is no such thing as "balanced" feedline unless
YOU actually DID something to FORCE it to be balanced. And the way to do
that is to insert a common-mode choke that enforces equal-and-opposite
currents at that particular location... though even then, it can do nothing
to prevent the regrowth of common-mode current elsewhere along the line.



73 from Ian GM3SEK



-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Wes
(N7WS)
Sent: 05 February 2016 00:18
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] Balun suggestions

I just pinched myself; I'm not dreaming and it's not April 1st, so I guess
you're serious.

You are also so wrong on so many points, I'm not going to waste time trying
to refute or correct them.

Jim, please ignore everything said below.

Wes  N7WS



On 2/4/2016 3:05 PM, Ron D'Eau Claire wrote:
> Your feed line will do the job by itself so no additional "balun" is
needed.
> Keep in mind that a 1:1 balun is really just a length of feed line, 
> usually wound on a toroidal core to make the required length shorter 
> than if it was in open air. The "old-school" baluns were just a pair of
air wound coils.
>
> If your balanced feed line is at least 1/4 wavelength long, the 
> currents will be "balanced" (equal and out of phase) at the antenna. 
> That assumes your antenna is perfectly balanced to provide a perfectly 
> balanced load, which "balanced" antennas almost never do. There are 
> just too many variables. So expect excellent results even with shorter 
> feed lines. The amount of radiation (or pickup) from the feed line 
> even at the rig end is small in any case.
>
> Connect one side of the open wire feed line to the KAT100 SO-239 
> center pin and the other to the KAT100 ground terminal.
>
> 73, Ron AC7AC
>
>
>
> -Original Message-
> K2/100 and KAT100 here.
>
> I am changing around my modest antenna configuration now.  I have been 
> using the K2/100 with my AH-4, and now wish to use the KAT100 with 
> balanced feedline antennas.
>
> What balun, homebrew or commercial, if any, should I use?  I almost 
> always run 5 watts, all CW.
>
> 73 de W6OGC Jim Allen
>
>
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>

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Re: [Elecraft] Balun suggestions

[Ron D'Eau Claire]

Agreed. I thought I made that point clear. And it's not just common-mode
currents. It all depends upon the load. A "dipole" antenna, for example, is
seldom exactly the same distance from surrounding objects on each half,
which will "unbalance" the load and so unbalance the currents on the feed
line. 

As Don points out, the currents emanating from the SO-239 connector are
balanced when you consider the current flowing on the outside of the center
conductor and on the inside of the coax shield (what goes on along the
outside of the shield is a totally different situation - RF flows along the
surface of a conductor so completely different currents can appear on the
inside and outside of the shield, assuming it's a good shield.)

73, Ron AC7AC


-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Ian
White
Sent: Friday, February 5, 2016 2:24 AM
To: 'Wes (N7WS)'; elecraft@mailman.qth.net
Subject: Re: [Elecraft] Balun suggestions

Wes's point is that twin feeder is not automatically "balanced" - very far
from it! Twin feeder happily supports both differential (equal and opposite,
balanced) currents and common-mode current at the same time.

So, in the real world, there is no such thing as "balanced" feedline unless
YOU actually DID something to FORCE it to be balanced. And the way to do
that is to insert a common-mode choke that enforces equal-and-opposite
currents at that particular location... though even then, it can do nothing
to prevent the regrowth of common-mode current elsewhere along the line.



73 from Ian GM3SEK



-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Wes
(N7WS)
Sent: 05 February 2016 00:18
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] Balun suggestions

I just pinched myself; I'm not dreaming and it's not April 1st, so I guess
you're serious.

You are also so wrong on so many points, I'm not going to waste time trying
to refute or correct them.

Jim, please ignore everything said below.

Wes  N7WS



On 2/4/2016 3:05 PM, Ron D'Eau Claire wrote:
> Your feed line will do the job by itself so no additional "balun" is
needed.
> Keep in mind that a 1:1 balun is really just a length of feed line, 
> usually wound on a toroidal core to make the required length shorter 
> than if it was in open air. The "old-school" baluns were just a pair 
> of
air wound coils.
>
> If your balanced feed line is at least 1/4 wavelength long, the 
> currents will be "balanced" (equal and out of phase) at the antenna.
> That assumes your antenna is perfectly balanced to provide a perfectly 
> balanced load, which "balanced" antennas almost never do. There are 
> just too many variables. So expect excellent results even with shorter 
> feed lines. The amount of radiation (or pickup) from the feed line 
> even at the rig end is small in any case.
>
> Connect one side of the open wire feed line to the KAT100 SO-239 
> center pin and the other to the KAT100 ground terminal.
>
> 73, Ron AC7AC
>
>
>
> -Original Message-
> K2/100 and KAT100 here.
>
> I am changing around my modest antenna configuration now.  I have been 
> using the K2/100 with my AH-4, and now wish to use the KAT100 with 
> balanced feedline antennas.
>
> What balun, homebrew or commercial, if any, should I use?  I almost 
> always run 5 watts, all CW.
>
> 73 de W6OGC Jim Allen
>
>
> __
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> w...@triconet.org
>

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Re: [Elecraft] Balun suggestions

[Ron D'Eau Claire]

Maxwells' famous equations first published in the 1870's have proven to be
extraordinarily accurate for all practical engineering purposes even after
all of these years: 

http://www.aproged.pt/biblioteca/MaxwellII.pdf

73, Ron AC7AC

 

-Original Message-

It may come as a shock to some, but almost everything fundamental about
electricity, electronics, audio, radio, and transmission lines was well
understood and documented nearly
100 years ago, and much of it decades earlier...


73, Jim K9YC
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Re: [Elecraft] Balun suggestions

[Ron D'Eau Claire]

Gee, Wes. It's only basic RF engineering. 

If you'd care to be specific about any objection, please do so. I'll be glad
to get into details on or off the reflector. 

73, Ron AC7AC

-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Wes
(N7WS)
Sent: Thursday, February 4, 2016 4:18 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] Balun suggestions

I just pinched myself; I'm not dreaming and it's not April 1st, so I guess
you're serious.

You are also so wrong on so many points, I'm not going to waste time trying
to refute or correct them.

Jim, please ignore everything said below.

Wes  N7WS



On 2/4/2016 3:05 PM, Ron D'Eau Claire wrote:
> Your feed line will do the job by itself so no additional "balun" is
needed.
> Keep in mind that a 1:1 balun is really just a length of feed line, 
> usually wound on a toroidal core to make the required length shorter 
> than if it was in open air. The "old-school" baluns were just a pair of
air wound coils.
>
> If your balanced feed line is at least 1/4 wavelength long, the 
> currents will be "balanced" (equal and out of phase) at the antenna. 
> That assumes your antenna is perfectly balanced to provide a perfectly 
> balanced load, which "balanced" antennas almost never do. There are 
> just too many variables. So expect excellent results even with shorter 
> feed lines. The amount of radiation (or pickup) from the feed line 
> even at the rig end is small in any case.
>
> Connect one side of the open wire feed line to the KAT100 SO-239 
> center pin and the other to the KAT100 ground terminal.
>
> 73, Ron AC7AC
>
>
>
> -Original Message-
> K2/100 and KAT100 here.
>
> I am changing around my modest antenna configuration now.  I have been 
> using the K2/100 with my AH-4, and now wish to use the KAT100 with 
> balanced feedline antennas.
>
> What balun, homebrew or commercial, if any, should I use?  I almost 
> always run 5 watts, all CW.
>
> 73 de W6OGC Jim Allen
>
>
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Re: [Elecraft] Balun suggestions

[David Rutledge via Elecraft]

 blockquote, div.yahoo_quoted { margin-left: 0 !important; border-left:1px 
#715FFA solid !important;  padding-left:1ex !important; background-color:white 
!important; }  Bob Rumsey, KZ5R of Balun Designs makes exceptional products & 
is always responsive if you have a question. I use several of his baluns. 
David RutledgeAL5M


Sent from Yahoo Mail for iPhone


On Thursday, February 4, 2016, 15:17, Walter Underwood  
wrote:

Balun Designs makes high quality baluns at fair prices.

http://www.balundesigns.com/ 

wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)

> On Feb 4, 2016, at 1:11 PM, Bert Craig  wrote:
> 
> I have to firmly vouch for Balun Concepts.
> 
> Sent from my android device.
> 
> -Original Message-
> From: Jim Allen 
> To: elecraft@mailman.qth.net
> Sent: Thu, 04 Feb 2016 15:55
> Subject: [Elecraft] Balun suggestions
> 
> K2/100 and KAT100 here.
> 
> I am changing around my modest antenna configuration now.  I have been using 
> the K2/100 with my AH-4, and now wish to use the KAT100 with balanced 
> feedline antennas.
> 
> What balun, homebrew or commercial, if any, should I use?  I almost always 
> run 5 watts, all CW.
> 
> 73 de W6OGC Jim Allen 
> 
> Sent from my iPad
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Re: [Elecraft] Balun suggestions

[Bert Craig]

I have to firmly vouch for Balun Concepts.

Sent from my android device.

-Original Message-
From: Jim Allen 
To: elecraft@mailman.qth.net
Sent: Thu, 04 Feb 2016 15:55
Subject: [Elecraft] Balun suggestions

K2/100 and KAT100 here.

I am changing around my modest antenna configuration now.  I have been using 
the K2/100 with my AH-4, and now wish to use the KAT100 with balanced feedline 
antennas.

What balun, homebrew or commercial, if any, should I use?  I almost always run 
5 watts, all CW.

73 de W6OGC Jim Allen 

Sent from my iPad
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Re: [Elecraft] Balun suggestions

[Ron D'Eau Claire]

Your feed line will do the job by itself so no additional "balun" is needed.
Keep in mind that a 1:1 balun is really just a length of feed line, usually
wound on a toroidal core to make the required length shorter than if it was
in open air. The "old-school" baluns were just a pair of air wound coils.

If your balanced feed line is at least 1/4 wavelength long, the currents
will be "balanced" (equal and out of phase) at the antenna. That assumes
your antenna is perfectly balanced to provide a perfectly balanced load,
which "balanced" antennas almost never do. There are just too many
variables. So expect excellent results even with shorter feed lines. The
amount of radiation (or pickup) from the feed line even at the rig end is
small in any case.

Connect one side of the open wire feed line to the KAT100 SO-239 center pin
and the other to the KAT100 ground terminal. 

73, Ron AC7AC



-Original Message-
K2/100 and KAT100 here.

I am changing around my modest antenna configuration now.  I have been using
the K2/100 with my AH-4, and now wish to use the KAT100 with balanced
feedline antennas.

What balun, homebrew or commercial, if any, should I use?  I almost always
run 5 watts, all CW.

73 de W6OGC Jim Allen 


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Re: [Elecraft] Balun suggestions

[Don Wilhelm]

Jim,

If your balanced feedline comes into the shack and you are running QRP, 
take a look at the Elecraft BL2.


73,
Don W3FPR

On 2/4/2016 3:55 PM, Jim Allen wrote:

K2/100 and KAT100 here.

I am changing around my modest antenna configuration now.  I have been using 
the K2/100 with my AH-4, and now wish to use the KAT100 with balanced feedline 
antennas.

What balun, homebrew or commercial, if any, should I use?  I almost always run 
5 watts, all CW.

73 de W6OGC Jim Allen

Sent from my iPad
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Re: [Elecraft] Balun suggestions

[Walter Underwood]

Balun Designs makes high quality baluns at fair prices.

http://www.balundesigns.com/ 

wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)

> On Feb 4, 2016, at 1:11 PM, Bert Craig  wrote:
> 
> I have to firmly vouch for Balun Concepts.
> 
> Sent from my android device.
> 
> -Original Message-
> From: Jim Allen 
> To: elecraft@mailman.qth.net
> Sent: Thu, 04 Feb 2016 15:55
> Subject: [Elecraft] Balun suggestions
> 
> K2/100 and KAT100 here.
> 
> I am changing around my modest antenna configuration now.  I have been using 
> the K2/100 with my AH-4, and now wish to use the KAT100 with balanced 
> feedline antennas.
> 
> What balun, homebrew or commercial, if any, should I use?  I almost always 
> run 5 watts, all CW.
> 
> 73 de W6OGC Jim Allen 
> 
> Sent from my iPad
> __
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Re: [Elecraft] Balun suggestions

[Mel Farrer via Elecraft]

Don't by-pass the Elecraft BL-2  $40  250 W 4:1 and 1:1 select able .
Mel, K6KBE

 

  From: Walter Underwood <wun...@wunderwood.org>
 To: Elecraft Reflector <elecraft@mailman.qth.net> 
 Sent: Thursday, February 4, 2016 1:17 PM
 Subject: Re: [Elecraft] Balun suggestions
   
Balun Designs makes high quality baluns at fair prices.

http://www.balundesigns.com/ <http://www.balundesigns.com/>

wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)

> On Feb 4, 2016, at 1:11 PM, Bert Craig <wa...@arrl.net> wrote:
> 
> I have to firmly vouch for Balun Concepts.
> 
> Sent from my android device.
> 
> -Original Message-
> From: Jim Allen <jalleninv...@gmail.com>
> To: elecraft@mailman.qth.net
> Sent: Thu, 04 Feb 2016 15:55
> Subject: [Elecraft] Balun suggestions
> 
> K2/100 and KAT100 here.
> 
> I am changing around my modest antenna configuration now.  I have been using 
> the K2/100 with my AH-4, and now wish to use the KAT100 with balanced 
> feedline antennas.
> 
> What balun, homebrew or commercial, if any, should I use?  I almost always 
> run 5 watts, all CW.
> 
> 73 de W6OGC Jim Allen 
> 
> Sent from my iPad
> __
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Re: [Elecraft] Balun suggestions

[Bob McGraw K4TAX]

As one that has personally used a balanced fed antennas for years, I 
suggest you review the info on this site.

 http://www.dj0ip.de/balun-stuff/ 

Good stuff on evaluating or building a proper balun.

And for open wire fed antennas:
http://www.dj0ip.de/open-wire-fed-ant/

To answer your question, a high power 1:1 current balun is likely best.  
Of course you could built a balanced tuner as I did.  Problem solved.  
That's another story.


Keep in mind that balun power ratings are for "matched" conditions. 
Which in fact is never the case with a center fed wire and open wire or 
a  balanced feed line.  At a mighty 5 watts it would not be of concern.


If at all possible, run the balanced feed line from the antenna feed 
point all the way to the operating position.  Keep the coax run between 
the tuner output and balun input as short as practical. After all, the 
reason to use balanced feed line is to take advantage of the low loss 
properties.


Never fear, the use of balanced feed line is not near as critical or 
fussy as the "masses" will so tout.  Many hams express fear in using 
balanced feed systems, largely because of what they have heard. Mostly 
because it frankly isn't fact.  Mine feeds a 256 ft center fed wire and 
comes down the tower supported on home made 9" PVC stand-offs, through 
the attic eve vent, across the roof rafters, and drops down through the 
ceiling to the tuner on the shelf above the desk.  Not bad for a 160M - 
10M antenna.{see my pix on QRZ.COM that shows a bit of the line 
going up the wall.}


73
Bob, K4TAX



On 2/4/2016 2:55 PM, Jim Allen wrote:

K2/100 and KAT100 here.

I am changing around my modest antenna configuration now.  I have been using 
the K2/100 with my AH-4, and now wish to use the KAT100 with balanced feedline 
antennas.

What balun, homebrew or commercial, if any, should I use?  I almost always run 
5 watts, all CW.

73 de W6OGC Jim Allen

Sent from my iPad
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Re: [Elecraft] Balun suggestions

[Jim Brown]

On Thu,2/4/2016 5:35 PM, Wes (N7WS) wrote:
Even though we often refer to the output of the KAT500 (or any other 
device that normally connects to a coaxial line, the currents on the 
output should be equal and opposite - which is the definition of 
balanced.


Sorry, that is NOT the definition of "balance." Balance is defined by 
equal potential to the reference plane, which for most land-based 
antennas is either the earth or the chassis of the transmitter that 
feeds it, which is usually ground referenced.


Consider the currents between the center conductor and the inside of 
the shield for coax.  They must be equal and opposite.  It is the 
common mode current on the outside of the feedline that produces any 
unbalance. 


No, the common mode current is the RESULT of imbalance. AND -- common 
mode current is present in two-wire feedlines when the antenna or the 
transmitter is unbalanced.  In those 2-wire feedlines, common mode 
current is the DIFFERENCE between the current in the two conductors.


Note also that feedlines have wavelength, and both voltage and current 
vary along the line. The DIFFERENTIAL voltage and current vary as a 
function of the behavior of the line as a transmission line, with Vf 
being that of the line. The COMMON MODE voltage and current vary along 
the line as a function of the line's behavior as an ANTENNA, where Vf is 
determined by the insulation on the outer conductor(s), so  is 0.98 - 0.99.


I laugh at those who attempt to measure current in both sides of a 
2-wire line and think that what they have measured is the current at 
every point on the line. It is not -- it's only the current at the point 
you measured it, and it's only right there if your measurement technique 
is without error. Which ain't easy.


73, Jim K9YC
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Re: [Elecraft] Balun suggestions

[Vic Rosenthal 4X6GP/K2VCO]

Jim,

You might find that on some bands your antenna tunes better with a 1:1 
balun and on others with a 4:1. Therefore, I recommend the Elecraft 
balun, which is switchable. It's rated at 250w so it should be adequate.


73,
Vic, 4X6GP/K2VCO
Rehovot, Israel
http://www.qsl.net/k2vco/

On 4 Feb 2016 22:55, Jim Allen wrote:

K2/100 and KAT100 here.

I am changing around my modest antenna configuration now.  I have
been using the K2/100 with my AH-4, and now wish to use the KAT100
with balanced feedline antennas.

What balun, homebrew or commercial, if any, should I use?  I almost
always run 5 watts, all CW.

73 de W6OGC Jim Allen

Sent from my iPad

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Re: [Elecraft] Balun suggestions

[Wes (N7WS)]

I was wrong.  Clearly, I'm dreaming.

On 2/4/2016 5:38 PM, Don Wilhelm wrote:

Wes,

I don't mean to be contentious, but under ideal conditions, what Ron said is 
true.  Even though we often refer to the output of the KAT500 (or any other 
device that normally connects to a coaxial line, the currents on the output 
should be equal and opposite - which is the definition of balanced.
Consider the currents between the center conductor and the inside of the 
shield for coax.  They must be equal and opposite.  It is the common mode 
current on the outside of the feedline that produces any unbalance.


So connecting a balanced feedline to a PL-259 is not so far fetched - 
providing the shell of the PL-259 (and enclosure of the KAT500) is not 
grounded.  If you have decided to ground your KAT500, then you would need to 
use a balun - so "it all depends". Be aware of "sneak grounds".


73,
Don W3FPR

On 2/4/2016 7:17 PM, Wes (N7WS) wrote:
I just pinched myself; I'm not dreaming and it's not April 1st, so I guess 
you're serious.


You are also so wrong on so many points, I'm not going to waste time trying 
to refute or correct them.


Jim, please ignore everything said below.

Wes  N7WS



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Re: [Elecraft] Balun suggestions

[Don Wilhelm]

Wes,

I don't mean to be contentious, but under ideal conditions, what Ron 
said is true.  Even though we often refer to the output of the KAT500 
(or any other device that normally connects to a coaxial line, the 
currents on the output should be equal and opposite - which is the 
definition of balanced.
Consider the currents between the center conductor and the inside of the 
shield for coax.  They must be equal and opposite.  It is the common 
mode current on the outside of the feedline that produces any unbalance.


So connecting a balanced feedline to a PL-259 is not so far fetched - 
providing the shell of the PL-259 (and enclosure of the KAT500) is not 
grounded.  If you have decided to ground your KAT500, then you would 
need to use a balun - so "it all depends".  Be aware of "sneak grounds".


73,
Don W3FPR

On 2/4/2016 7:17 PM, Wes (N7WS) wrote:
I just pinched myself; I'm not dreaming and it's not April 1st, so I 
guess you're serious.


You are also so wrong on so many points, I'm not going to waste time 
trying to refute or correct them.


Jim, please ignore everything said below.

Wes  N7WS



On 2/4/2016 3:05 PM, Ron D'Eau Claire wrote:
Your feed line will do the job by itself so no additional "balun" is 
needed.
Keep in mind that a 1:1 balun is really just a length of feed line, 
usually
wound on a toroidal core to make the required length shorter than if 
it was
in open air. The "old-school" baluns were just a pair of air wound 
coils.


If your balanced feed line is at least 1/4 wavelength long, the currents
will be "balanced" (equal and out of phase) at the antenna. That assumes
your antenna is perfectly balanced to provide a perfectly balanced load,
which "balanced" antennas almost never do. There are just too many
variables. So expect excellent results even with shorter feed lines. The
amount of radiation (or pickup) from the feed line even at the rig 
end is

small in any case.

Connect one side of the open wire feed line to the KAT100 SO-239 
center pin

and the other to the KAT100 ground terminal.

73, Ron AC7AC



-Original Message-
K2/100 and KAT100 here.

I am changing around my modest antenna configuration now.  I have 
been using

the K2/100 with my AH-4, and now wish to use the KAT100 with balanced
feedline antennas.

What balun, homebrew or commercial, if any, should I use?  I almost 
always

run 5 watts, all CW.

73 de W6OGC Jim Allen


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Re: [Elecraft] Balun suggestions

[Jim Brown]

On Thu,2/4/2016 12:55 PM, Jim Allen wrote:

What balun, homebrew or commercial, if any, should I use?  I almost always run 
5 watts, all CW.


k9yc.com/RFI-Ham.pdf  Since you're running QRP, a single 2.4-in o.d. #31 
core is all you need. Study the data in Appendix One for small diameter 
wire, and wind the number of turns of your coax through it that puts the 
impedance peak in the frequency range where you want to operate.


73, Jim K9YC
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Re: [Elecraft] Balun Sugestions

[Jim Allen]

Thanks, Bob.

I have scoured Rick's website for some time, on this and other topics, and 
corresponded with him extensively about various ideas.  I've also read dozens 
of web pages about baluns, any number of threads at QRZ.com on the topic as 
well.  There are confusing, contradictory and often mutually exclusive points 
of view and no clear direction how to go for those of us whose understanding of 
these things is fairly shallow.  Each approach has disadvantages, detractors 
and claimed limitations, it seems.

I could easily make a balun with a ferrite toroid core, as shown by G3TXQ with 
10-12 turns of some RG8x, which I have in hand, pop it in a box with a couple 
of connectors, and have a go with that.  I am sensitive to losses, since with 
QRP and modest antennas due to external limitations, I have no dbs to waste.  I 
need to have one, or two, good multi band antennas.  I try to avoid store 
bought antennas, and anything with radials are a no-go here on the Rock Ranch..

I just started using the KAT100.  Pretty slick.  With a good quality balun, it 
has some attractive features, replacing the AH-4.  I have also been tempted by 
the MFJ974HB balanced tuner.  No balun needed but no KAT100 needed either.  I 
wish I could find the parts to roll my own!

I have been using balanced feed lines for the various antennas since I moved 
here ~30 months ago with gratifying results.

Keep the suggestions coming!

73 de W6OGC Jim Allen 
Message: 23
Date: Thu, 4 Feb 2016 17:10:39 -0600
From: Bob McGraw K4TAX <rmcg...@blomand.net>
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] Balun suggestions
Message-ID: <56b3da6f.3090...@blomand.net>
Content-Type: text/plain; charset=windows-1252; format=flowed

As one that has personally used a balanced fed antennas for years, I 
suggest you review the info on this site.
 http://www.dj0ip.de/balun-stuff/ <http://www.dj0ip.de/balun-stuff/>

Good stuff on evaluating or building a proper balun.

And for open wire fed antennas:
http://www.dj0ip.de/open-wire-fed-ant/

To answer your question, a high power 1:1 current balun is likely best.  
Of course you could built a balanced tuner as I did.  Problem solved.  
That's another story.

Keep in mind that balun power ratings are for "matched" conditions. 
Which in fact is never the case with a center fed wire and open wire or 
a  balanced feed line.  At a mighty 5 watts it would not be of concern.

If at all possible, run the balanced feed line from the antenna feed 
point all the way to the operating position.  Keep the coax run between 
the tuner output and balun input as short as practical. After all, the 
reason to use balanced feed line is to take advantage of the low loss 
properties.

Never fear, the use of balanced feed line is not near as critical or 
fussy as the "masses" will so tout.  Many hams express fear in using 
balanced feed systems, largely because of what they have heard. Mostly 
because it frankly isn't fact.  Mine feeds a 256 ft center fed wire and 
comes down the tower supported on home made 9" PVC stand-offs, through 
the attic eve vent, across the roof rafters, and drops down through the 
ceiling to the tuner on the shelf above the desk.  Not bad for a 160M - 
10M antenna.{see my pix on QRZ.COM that shows a bit of the line 
going up the wall.}

73
Bob, K4TAX

Sent from my iPad
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Re: [Elecraft] Balun suggestions

[Jim Miller]

I suggest reading work by w9cf before getting concerned about balancing tuners. 

http://fermi.la.asu.edu/w9cf/articles/balun/index.html

On Feb 4, 2016, at 7:38 PM, Don Wilhelm  wrote:

Wes,

I don't mean to be contentious, but under ideal conditions, what Ron said is 
true.  Even though we often refer to the output of the KAT500 (or any other 
device that normally connects to a coaxial line, the currents on the output 
should be equal and opposite - which is the definition of balanced.
Consider the currents between the center conductor and the inside of the shield 
for coax.  They must be equal and opposite.  It is the common mode current on 
the outside of the feedline that produces any unbalance.

So connecting a balanced feedline to a PL-259 is not so far fetched - providing 
the shell of the PL-259 (and enclosure of the KAT500) is not grounded.  If you 
have decided to ground your KAT500, then you would need to use a balun - so "it 
all depends".  Be aware of "sneak grounds".

73,
Don W3FPR

> On 2/4/2016 7:17 PM, Wes (N7WS) wrote:
> I just pinched myself; I'm not dreaming and it's not April 1st, so I guess 
> you're serious.
> 
> You are also so wrong on so many points, I'm not going to waste time trying 
> to refute or correct them.
> 
> Jim, please ignore everything said below.
> 
> Wes  N7WS
> 
> 
> 
>> On 2/4/2016 3:05 PM, Ron D'Eau Claire wrote:
>> Your feed line will do the job by itself so no additional "balun" is needed.
>> Keep in mind that a 1:1 balun is really just a length of feed line, usually
>> wound on a toroidal core to make the required length shorter than if it was
>> in open air. The "old-school" baluns were just a pair of air wound coils.
>> 
>> If your balanced feed line is at least 1/4 wavelength long, the currents
>> will be "balanced" (equal and out of phase) at the antenna. That assumes
>> your antenna is perfectly balanced to provide a perfectly balanced load,
>> which "balanced" antennas almost never do. There are just too many
>> variables. So expect excellent results even with shorter feed lines. The
>> amount of radiation (or pickup) from the feed line even at the rig end is
>> small in any case.
>> 
>> Connect one side of the open wire feed line to the KAT100 SO-239 center pin
>> and the other to the KAT100 ground terminal.
>> 
>> 73, Ron AC7AC
>> 
>> 
>> 
>> -Original Message-
>> K2/100 and KAT100 here.
>> 
>> I am changing around my modest antenna configuration now.  I have been using
>> the K2/100 with my AH-4, and now wish to use the KAT100 with balanced
>> feedline antennas.
>> 
>> What balun, homebrew or commercial, if any, should I use?  I almost always
>> run 5 watts, all CW.
>> 
>> 73 de W6OGC Jim Allen
>> 
>> 
>> __
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
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>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
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> 
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Re: [Elecraft] Balun suggestions

[Wes (N7WS)]

I just pinched myself; I'm not dreaming and it's not April 1st, so I guess 
you're serious.


You are also so wrong on so many points, I'm not going to waste time trying to 
refute or correct them.


Jim, please ignore everything said below.

Wes  N7WS



On 2/4/2016 3:05 PM, Ron D'Eau Claire wrote:

Your feed line will do the job by itself so no additional "balun" is needed.
Keep in mind that a 1:1 balun is really just a length of feed line, usually
wound on a toroidal core to make the required length shorter than if it was
in open air. The "old-school" baluns were just a pair of air wound coils.

If your balanced feed line is at least 1/4 wavelength long, the currents
will be "balanced" (equal and out of phase) at the antenna. That assumes
your antenna is perfectly balanced to provide a perfectly balanced load,
which "balanced" antennas almost never do. There are just too many
variables. So expect excellent results even with shorter feed lines. The
amount of radiation (or pickup) from the feed line even at the rig end is
small in any case.

Connect one side of the open wire feed line to the KAT100 SO-239 center pin
and the other to the KAT100 ground terminal.

73, Ron AC7AC



-Original Message-
K2/100 and KAT100 here.

I am changing around my modest antenna configuration now.  I have been using
the K2/100 with my AH-4, and now wish to use the KAT100 with balanced
feedline antennas.

What balun, homebrew or commercial, if any, should I use?  I almost always
run 5 watts, all CW.

73 de W6OGC Jim Allen


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Re: [Elecraft] Balun suggestions

[Jim Brown]

On Thu,2/4/2016 12:55 PM, Jim Allen wrote:

I am changing around my modest antenna configuration now.  I have been using 
the K2/100 with my AH-4, and now wish to use the KAT100 with balanced feedline 
antennas.

What balun, homebrew or commercial, if any, should I use?  I almost always run 
5 watts, all CW


You didn't say what your antenna is or what bands you want to work. 
Antennas, feedlines, and tuners are a SYSTEM, and must be considered as 
a system. Why do you want to use "balanced" line? Has someone told you 
it's lower loss, and you can use any random wire (or some "magic" length 
of wire on all bands?


Are you trying to use a non-resonant antenna on multiple bands? If so, 
why? Is that the only sort of antenna you can hang? There are serious 
issues with this sort of antenna. First, there can be significant 
feedline losses. Second, these antennas are nearly impossible to choke 
to kill common mode noise, so they can be noisy. Off-center-fed antennas 
are unbalanced by their nature, so they're inherently noisy. Even a 
center-fed antenna will be unbalanced by its surroundings -- sloping 
ground, variable height, proximity to other conductors on one end but 
not the other, etc.


Take a look at the antenna planning tutorials on my website. All of the 
options shown there are superior to most "all-band" wires.


73, Jim K9YC


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Re: [Elecraft] Balun suggestions

[Don Wilhelm]

Wes and all,

Yes, that is one source of "sneak ground".  A balun will cure that 
condition.


73,
Don W3FPR

On 2/4/2016 11:48 PM, Wes (N7WS) wrote:
You mean like that "sneak ground" from the input of the tuner back to 
the grounded amp or exciter?  Or are they floating too?


On 2/4/2016 5:38 PM, Don Wilhelm wrote:


So connecting a balanced feedline to a PL-259 is not so far fetched - 
providing the shell of the PL-259 (and enclosure of the KAT500) is 
not grounded.  If you have decided to ground your KAT500, then you 
would need to use a balun - so "it all depends". Be aware of "sneak 
grounds".




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Re: [Elecraft] Balun suggestions

[Wes (N7WS)]

You mean like that "sneak ground" from the input of the tuner back to the 
grounded amp or exciter?  Or are they floating too?


On 2/4/2016 5:38 PM, Don Wilhelm wrote:


So connecting a balanced feedline to a PL-259 is not so far fetched - 
providing the shell of the PL-259 (and enclosure of the KAT500) is not 
grounded.  If you have decided to ground your KAT500, then you would need to 
use a balun - so "it all depends". Be aware of "sneak grounds".


73,
Don W3FPR



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Re: [Elecraft] Balun Ground Connection

[Guy Olinger K2AV]

First thing I would say it to literally model your back yard,
including all your antennas and feedlines.  In the same model.  That
may cost you some for serious models that will handle that much wire.
Or you can visit a friend who has the software and do it on his.

In our head, among all the miscellaneous mental simplification devices
we have to understand the world, are some often expressed, like coax
laying on the ground is out of play and can be forgotten.  It's not
true of course, and it's hardly the only common misnomer.  The truth
comes up when you uncover a couple dozen surprises about what is
really going on and places where common mode current on conductors is
playing havoc.  There is no simple rule, but the site model of your
yard is worth it.

One may get away with a lot of stuff most of the time, even nearly all
of the time, but the typical backyard is so random compared to others'
backyards that no inviolable rules really exist.

One problem with an elevated long run of 450 ohm line placed ~ 900
volts of common mode voltage across a blocking point running QRO and
was destroying ferrite devices.  Literally modeling the transmission
line in the site model identified the reason why, it was just an
unlucky length in an unlucky place.  It was also dissipating a lot of
power.  Some redesign, and transformer winding, and problem gone.

It was obvious in the model. My intuitive mental simplification
device about how that worked was just plain wrong.  Do a site model.
There was real increase in TX radiated power after that was fixed.

There is much about antennas that simply is NOT intuitive.  The model
is not fooled.  I realize this suggestion has all the attractiveness
of being told to take out the trash, mow the grass, or plow the
garden, paint the house, or complete putting down and burying the
radials to have a truly dense field. But if you have one of those
surprises Heh, heh.

IF you have the site model, you can also model insertion of common
mode blocks, adding grounds, discovering where they have effect.

LIke I said, taking out the trash is neither elegant nor entertaining,
but highly useful overall.

73, Guy.

On Fri, Sep 21, 2012 at 1:24 AM,  zen...@netspace.net.au wrote:


 Hi Rich,

 This DXE balun is just a hefty 1:1 choke balun  It's a high grade
 coax (50ohm) wrapped through ferrite cores.  The balanced terminals
 are floating and the unbalanced end is connected to the aluminium
 housing and the shield of the 6 foot length of RG213 coax which
 connects the balun and my tuner.  I have a balun inside my tuner too,
 but I don't use it:  it's a 4:1 current balun and in this application
 with a multi-band loop,   I prefer to use the external 1:1 balun.

 I agree - with my loop , anything that changes the feedline length,
 even by smallish amounts, alters the impedance seen by the tuner at
 the end of the line and the manual tuner settings change on (usually)
 multiple bands and the KAT3 has to reconfigure its LC settings.  I
 expected that, as a function of the impedance transforming effect of
 the feedline, but what I didn't expect was the very significant
 difference that different  shack grounding arrangements would make
 to the whole process of matching the antenna system at the shack end
 of the feedline.

 About the common mode current that I'm measuring on the coax between
 the balun and the tuner:  Yes, I assume the 1:1 balun has sufficient
 common mode impedance to be preventing common mode current standing
 waves on unbalanced side of it.   But I think what I'm measuring is
 current that's being induced in the coax shield because it's lying in
 the near field of radiation of the loop.  Again, what is a mystery to
 me is how changing the grounding arrangement on the balun could affect
 the magnitude of that.

 I find this intruguing, but for the moment, I've put the clip on
 ammeter away.  I'm going to forget it, while i digest this, and go
 and play on 20m instead.

 Thanks for all the comments I've rec'd, on and off the list.

 73

 John

 VK7JB

 -Original Message-
  From: elecraft-boun...@mailman.qth.net
 [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Richard Fjeld
  Sent: Friday, 21 September 2012 1:00 PM
  To: elecraft posting
  Subject: [Elecraft] Fw: Balun Ground Connection



 John,

 It is unfortunate that we can't see a schematic of how the balun is
 wired.

 I have thought of doing that same thing to be able to use an ATU.

 Presently, I have an 80 meter loop fed with homebrew 450 ohm ladder
 line to

 a tuner with a 1:1 balun within.  It works beautifully on all
 bands.  I wish

 I had done it many years ago.



 As for your grounding the coax at both ends, I effectively do that
 here also

 on my coax switch with coax to my K3 which is also grounded.  So
 that is why

 it would be necessary to 

Re: [Elecraft] Balun Ground Connection

[Jim Brown]

On 9/20/2012 12:53 PM, Jim Harris wrote:
 I found that by connecting the balun ground to my station ground I had 25 
 SWR on all bands.  I just let it float..no problems so far.

That suggests something wrong with your antenna system.

73, Jim K9YC
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Re: [Elecraft] Balun Ground Connection

[Don Wilhelm]

Jim.

I would strongly suggest that is an indication of a problem in your 
antenna system somewhere (my first guess would be between the 
transmitter and the balun).  I would start by substituting the coax to 
the balun.

73,
Don W3FPR

On 9/20/2012 3:53 PM, Jim Harris wrote:
 John,
 I found that by connecting the balun ground to my station ground I had 25 
 SWR on all bands.  I just let it float..no problems so far.
 73
 Jim, W0EM


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Re: [Elecraft] Balun Ground Connection

[zendoc]

Hi Jim  group

I did an experiment today and tied the balun case/coax shield to station ground 
via the stud. 

I found 2 things: 

# 1 the manual tuner settings required for 1:1 match changed on all bands, but 
the KAT3 and manual tuner were still able to find a 1:1.0 match on all bands 
80m - 10m. 

#2 where I had no detectable common mode current on the coax shield prior to 
connecting the balun to ground, I now have 15-20mA on 20 and 40m, as measured 
with my calibrated clip on ammeter.  There's also now some RF on my tx audio, 
where before it was clean. 

I'm wondering if the coax shield between the balun and tuner IS functioning as 
part of this loop antenna system and grounding its shield before the tuner  is 
introducing more imbalance?  

I'm no expert, but this is interesting. 

73,
John
VK7JB



 Original Message --

 

 John, 
 I found that by connecting the balun ground to my station ground I
had 25 SWR on all bands. I just let it float..no problems so far.

 73 
Jim, W0EM 
   
John
VK7JB



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Re: [Elecraft] Balun Ground Connection

[Jim Harris]

John,
I'm not surprised at your findings in light of my experience.  Regarding the 
ATUs being able to tune in this case, I'm not surprised.  Elecraft tuners will 
match nearly a complete open and short...been there, done that.  I really 
wish they were limited to something like 6:1 to prevent that.  Above that SWR 
RF energy is grossly wasted, IMHO.
It seems for some reason that I don't know about at the moment, when the balun 
case ground is connected to station ground it somehow makes a major change in 
the antenna/coax system.  I've replaced most of the coax in all my antenna 
systems in the last month so I'm leaning toward some other explanation.  When I 
get some spare time this weekend I will try to take a further look at it.

73



Jim, W0EM

--- On Thu, 9/20/12, zen...@netspace.net.au zen...@netspace.net.au wrote:

From: zen...@netspace.net.au zen...@netspace.net.au
Subject: Re: Balun Ground Connection
To: 'Jim Harris' jim.w...@yahoo.com, zen...@netspace.net.au, 'Elecraft 
Email' elecraft@mailman.qth.net
Date: Thursday, September 20, 2012, 9:50 PM

Hi Jim  group

I did an experiment today and tied the balun case/coax shield to station ground 
via the stud. 

I found 2 things: 

# 1 the manual tuner settings required for 1:1 match changed on all bands, but 
the KAT3 and manual tuner were still able to find a 1:1.0 match on all bands 
80m - 10m. 

#2 where I had no detectable common mode current on the coax shield prior to 
connecting the balun to ground, I now have 15-20mA on 20 and 40m, as measured 
with my calibrated clip on ammeter.  There's also now some RF on my tx audio, 
where before it was clean. 

I'm wondering if the coax shield between the balun and tuner IS functioning as 
part of this loop antenna system and grounding its shield before the tuner  is 
introducing more imbalance?  

I'm no expert, but this is interesting. 

73,
John
VK7JB



 Original Message --

 

 John, 
 I found that by connecting the balun ground to my station ground I
had 25 SWR on all bands. I just let it float..no problems so far.

 73 
Jim, W0EM 
   
John
VK7JB



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Re: [Elecraft] Balun at input or output of tuner

[Jim Brown]

On 12/13/2011 12:53 PM, David Herring wrote:
 I'd like to ask a few questions.

David,

I hardly know where to begin in responding to your question. First, if 
you want a self-supporting vertical antenna for 30-10M, there are some 
really good choices that you can buy, that can be easily installed, that 
can be fed with 50 ohm coax, that don't require radials, and that don't 
require a balanced tuner. Loss in the feedline should be quite small if 
you use RG8 (or even RG8X). Look at the Hy-Gain AV-640, which one of my 
friends has used to work a lot of DX and do contesting from a small city 
lot. You should use one of my chokes at the feedpoint of this antenna. 
See my RFI tutorial, previously referenced.

IMO, balanced tuners and so-called balanced line are highly over-rated 
solutions to problems that don't exist, or that could be better solved 
with other far simpler and less costly means.  IMO, the only GOOD use of 
high impedance parallel wire feedlines is for very long runs -- 500 ft 
or more. Likewise, I am not a fan of all-band non-resonant dipole 
antennas, primarily because it is mechanically difficult choke them at 
their feedpoint, which makes them noisy and puts RF on the feedline, but 
also because their directional patterns vary widely with frequency.  
Since you're trying to make a vertical work on all bands, I'm assuming 
that horizontal antennas are not practical for you, hence the 
recommendation for the AV-640.  I'm not a fan of compact, multi-band 
verticals below 40M because their efficiency tends to be poor, but at 
30M and above they can work quite well.

As to RF in the shack -- nearly all RF in the shack problems are the 
result of Pin One Problems in equipment. See the RFI tutorial for an 
explanation and solutions.  Also see the pdf on Ham Interfacing for 
detailed instructions about bonding all of your gear together with short 
lengths of copper wire. This kills hum and buzz, and makes a big dent in 
the RFI you're experiencing.  In extreme cases you may need to add 
chokes to individual cables.

http://audiosystemsgroup.com/publish.htm

73, Jim K9YC
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Re: [Elecraft] Balun at input or output of tuner

[David Herring]

Hi Jim,

Thanks for the tip on the AV-640...I'll surely look into that.  I am looking 
for a self-supporting solution to minimize my impact upon the XYL's view (to 
her credit, she's been incredibly patient and understanding about that). The 
home brew vertical dipole I'm running now requires guys which isn't pretty in 
her opinion. 

You're right about my not having space for horizontal antennas.  I had 
shoe-horned in here an inverted-vee for a while, but that was little more than 
a cloud warmer -- my vertical dipole out-performs it 10 to 1.

I went with the vertical dipole because I'm leery of verticals without 
radials...I see the AV-640 has what appears to be a ground plane, so that may 
work out just fine.

I have been reading your papers and am beginning to have a fair understanding 
of the pin 1 problem, though I admit I have not gotten very far in physically 
implementing it.  I do notice the amount of RF in the shack varies a lot if I 
mess around with the position the 450-ohm window line.  That's what piqued my 
interest when I read about the use of a CM choke at the feed point of balanced 
lines...If that helped to restore balance in the balanced feeder, my thought 
was that might reduce feed line radiation enough to make my relatively minor 
RF-in-the-shack problem effectively go away.  And if it improved my radiation 
pattern in the process, so much the better.

But I am seeing now that line of thinking was a bit simplistic and the issue is 
bigger than that.

Jim, thanks for the response to my post and for sharing your knowledge in 
general...I for one appreciate it.

73  Aloha,

David
AH6TD


On Dec 16, 2011, at 9:00 AM, Jim Brown wrote:

 On 12/13/2011 12:53 PM, David Herring wrote:
 I'd like to ask a few questions.
 
 David,
 
 I hardly know where to begin in responding to your question. First, if 
 you want a self-supporting vertical antenna for 30-10M, there are some 
 really good choices that you can buy, that can be easily installed, that 
 can be fed with 50 ohm coax, that don't require radials, and that don't 
 require a balanced tuner. Loss in the feedline should be quite small if 
 you use RG8 (or even RG8X). Look at the Hy-Gain AV-640, which one of my 
 friends has used to work a lot of DX and do contesting from a small city 
 lot. You should use one of my chokes at the feedpoint of this antenna. 
 See my RFI tutorial, previously referenced.
 
 IMO, balanced tuners and so-called balanced line are highly over-rated 
 solutions to problems that don't exist, or that could be better solved 
 with other far simpler and less costly means.  IMO, the only GOOD use of 
 high impedance parallel wire feedlines is for very long runs -- 500 ft 
 or more. Likewise, I am not a fan of all-band non-resonant dipole 
 antennas, primarily because it is mechanically difficult choke them at 
 their feedpoint, which makes them noisy and puts RF on the feedline, but 
 also because their directional patterns vary widely with frequency.  
 Since you're trying to make a vertical work on all bands, I'm assuming 
 that horizontal antennas are not practical for you, hence the 
 recommendation for the AV-640.  I'm not a fan of compact, multi-band 
 verticals below 40M because their efficiency tends to be poor, but at 
 30M and above they can work quite well.
 
 As to RF in the shack -- nearly all RF in the shack problems are the 
 result of Pin One Problems in equipment. See the RFI tutorial for an 
 explanation and solutions.  Also see the pdf on Ham Interfacing for 
 detailed instructions about bonding all of your gear together with short 
 lengths of copper wire. This kills hum and buzz, and makes a big dent in 
 the RFI you're experiencing.  In extreme cases you may need to add 
 chokes to individual cables.
 
 http://audiosystemsgroup.com/publish.htm
 
 73, Jim K9YC
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Re: [Elecraft] Balun at input or output of tuner

[Jim Brown]

On 12/14/2011 8:29 PM, Ross Primrose N4RP wrote:
 Is it just me, or does that paragraph have a glaring typo in it 

Yep!  Thanks.  It should read, if we put the choke at the antenna, the 
differential loss . . . . . 

Jim K9YC
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Re: [Elecraft] Balun at input or output of tuner

[Cortland Richmond]

I hesitate to step between Dean and anyone else but... it seems to me 
that a Balun with good enough common mode choking should fulfill all the 
isolation requirements we might have.  The isolation any Balun provides 
takes place at the point it is inserted, so a Balun built for 50 Ohms 
may be used at the input to a (floating) tuner without our necessarily 
being worse off than putting it on a tuner output -- if we can tolerate 
what imbalance exists on the load side on the load and resulting RF on 
the tuner chassis.   We must make that RF low enough to live with, for 
which we don't need perfect isolation, only _enough_.   It may go 
without saying that we can put CM chokes anywhere we want -- and as may 
times as we want (losses permitting).



This may be moot; in his article/A Better Antenna-Tuner Balun/, QEX, 
Sept/Oct 2005, ZS1AN noted the problem with voltage Baluns and 
inherently unbalanced loads, and proposed a combined voltage and current 
balun to gain the advantages of both.  excerpt:

/...analyze the performance of the 1:1 current balun and the 4:1 voltage 
balun in this application.
The analysis shows that the current balun operates effectively only for 
small load impedances,
while the voltage balun is effective only if the load impedance is well 
balanced with respect to ground.

I then introduce a new design: the hybrid balun, which overcomes these 
limitations of the voltage
and current baluns. It can operate with much higher load impedances than 
can current baluns and with
unbalanced load impedances that voltage baluns could not drive effectively.
/

Cortland
KA5S

On 12/14/2011 7:56 PM, Don Wilhelm wrote:
 Dean,

 The last two paragraphs of your writeup do not seem relevant to the
 discussion of balun (CM choke) at the input or output  Those paragraphs
 deal with operating coax at a very high 60:1 SWR, and neither support
 nor agree with the other points.

 Consider the following:  A situation where the windowsill connection is
 20 feet away from the tuner output.  The balun has the same loss no
 matter where it is placed, so lets assume it is placed at the output.

 Now, consider that the connection between the tuner output and the
 windowsill is with 20 feet of RG-213.  The balanced line is connected
 directly to the coax (no balun).  By the analysis presented, the loss
 will be exactly the same as with the balun connected at the windowsill
 end of the coax.

 Both conditions are electrically the same (If that point is arguable,
 then the balun at the tuner input is just as arguable).

 If we can extend this argument, we would be able to conclude that it
 makes no difference on a coax fed antenna whether the balun is placed at
 the antenna or at the tuner output - no matter whether the feedline is
 coax or balanced line.  Oh, yes, both the coax or balanced line must be
 isolated and run with the same rules normally applied to balanced line.
 The point is that while theory says it makes no difference, it is
 impossible to achieve that perfect isolation, so the argument falls apart.

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Re: [Elecraft] Balun at input or output of tuner

[Don Wilhelm]

Dean,

The last two paragraphs of your writeup do not seem relevant to the 
discussion of balun (CM choke) at the input or output  Those paragraphs 
deal with operating coax at a very high 60:1 SWR, and neither support 
nor agree with the other points.

Consider the following:  A situation where the windowsill connection is 
20 feet away from the tuner output.  The balun has the same loss no 
matter where it is placed, so lets assume it is placed at the output.

Now, consider that the connection between the tuner output and the 
windowsill is with 20 feet of RG-213.  The balanced line is connected 
directly to the coax (no balun).  By the analysis presented, the loss 
will be exactly the same as with the balun connected at the windowsill 
end of the coax.

Both conditions are electrically the same (If that point is arguable, 
then the balun at the tuner input is just as arguable).

If we can extend this argument, we would be able to conclude that it 
makes no difference on a coax fed antenna whether the balun is placed at 
the antenna or at the tuner output - no matter whether the feedline is 
coax or balanced line.  Oh, yes, both the coax or balanced line must be 
isolated and run with the same rules normally applied to balanced line.  
The point is that while theory says it makes no difference, it is 
impossible to achieve that perfect isolation, so the argument falls apart.

Because most would not consider connecting a balanced line to coax 
without an intervening balun because we have been taught that we must 
preserve balance in order for things to be correct.
The fallacy I see with the  balun at the input vs. balun at the output 
argument is that with the balun on the input, everything that follows 
must be perfectly isolated from ground - and that is difficult to 
achieve when all physical things are considered - if there are *any* 
strays, it defeats the principle of perfect isolation.  That is also 
what makes my example of the 20 feet of coax at the balanced output of a 
tuner not a practical consideration - one cannot easily achieve equal 
coupling of the center conductor and shield if there are any surrounding 
objects.  That fact makes the unbalanced tuner with an input balun not 
practical  because that perfect isolation is just as (or more) difficult 
and expensive to achieve than it would be to implement a balanced network.

73,
Don W3FPR


On 12/12/2011 3:38 PM, Dean Straw wrote:
   While we're at it, let's look at the potential loss due to line
 losses at a CM choke balun placed in the wrong place in an antenna system.
 Assume the common scenario where a balanced antenna is fed with open-wire
 transmission line to a 1:1 common-mode choke balun located at the shack
 window. From the balun at the window the ham uses, say, a 20-foot section of
 RG-213 to the antenna tuner (which in this case is an unbalanced tuning
 network). Assume again that the CM choke balun uses three feet of RG-213
 wound on the appropriate ferrite donuts to achieve the target common-mode
 impedance of 5000 ohms so that common-mode currents are choked off properly.

   The total length of RG-213 is now 23 feet. Again, we'll present the
 balun at the windowsill with a load of 3000 ohms. The overall
 differential-mode loss in 23 feet of RG-213 is 4.534 dB, nearly 4 dB worse
 than connecting the open-wire line directly to a tuner with a CM choke balun
 at its output! Ouch, that's a lot of wasted power.

 73, Dean, N6BV

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Re: [Elecraft] Balun at input or output of tuner

[Jim Brown]

On 12/14/2011 4:59 PM, Don Wilhelm wrote:
 The balun has the same loss no
 matter where it is placed, so lets assume it is placed at the output.

There we go with that nasty word again (balun) -- we're talking about a 
common mode choke, right? :)

The problem is more complex than it looks.  Let's say we have a matched 
200 ft line with loss of 3dB (to make the arithmetic simple), the choke 
is wound with the same Z as the rest of the line, and we drive the line 
with 1kW. If we put the choke at the transmitter, the differential loss 
in the choke will be half of what it would be at the transmitter end.

Now, let's say we have a mismatched line that we're driving with that 
same 1kW, and the Zo of the choke is still the same as the Zo of the 
rest of the line,  To compute the differential loss in the choke, we 
must determine the current distribution along the line so that we know 
the current in the choke. Now, the TOTAL differential loss in the line 
will be the same no matter where the choke is, but since the coax going 
through the choke is coiled up, its dissipation is more concentrated 
than the rest of the line, and it's thermally coupled to the core, and 
maybe it's also in an enclosure.

The real world may be even more complicated -- perhaps  the Zo of the 
choke different from the Zo of the rest of the line.  Or perhaps there's 
some sort of impedance transformer, not a simple common mode choke.  
Again, we've got to work through the transmission line problem(s) and 
find the current in the choke.

And we haven't even talked about common mode dissipation yet. :)

73, Jim K9YC
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Re: [Elecraft] Balun at input or output of tuner

[Paul Christensen]

Dean's example is still valid.  By placing the CM Choke at the wrong 
distance of 20 feet from the tuner, the 3,000 ohm Z presented at the balun 
in addition to the extra 20 feet of line can create substantial mismatch 
loss (i.e., additional loss due to VSWR).  The choke simply adds three feet 
of coax for a total of 23 feet from the tuner.  If the balanced line were 
dragged into the shack to reach the tuner output, loss is much less and the 
remaining loss is the result of the severe mismatch and heating occurring 
over just 3 feet of cable instead of 23 feet.  Of course, the tuner will 
have some loss of its own that we haven't considered.  But the problem is 
the extra coax length under a high mismatch conditions -- and not that a CM 
choke is present in the line, notwithstanding the three feet of coax used in 
its windings.

Prior authors have focused almost entirely on the CM choke's line balance 
and common mode reactance attributes and not systematic loss.  So, gulp if 
placement of the CM choke at the tuner input results in no better balance, 
but no worse balance, then clearly, system loss in many situations (e.g., 
multi-band dipoles and loops) will be less and that configuration may be 
preferred.  OTOH, if balance suffers, then one must look at whether loss or 
line balance or choke heating is more important, depending on the mismatch 
magnitude appearing at a CM choke located at the tuner output -- or at some 
wrong distance away from the tuner.

Paul, W9AC

- Original Message - 
From: Don Wilhelm w3...@embarqmail.com
To: Dean Straw n...@arrl.net
Cc: elecraft@mailman.qth.net
Sent: Wednesday, December 14, 2011 7:59 PM
Subject: Re: [Elecraft] Balun at input or output of tuner


 Dean,

 The last two paragraphs of your writeup do not seem relevant to the
 discussion of balun (CM choke) at the input or output  Those paragraphs
 deal with operating coax at a very high 60:1 SWR, and neither support
 nor agree with the other points.

 Consider the following:  A situation where the windowsill connection is
 20 feet away from the tuner output.  The balun has the same loss no
 matter where it is placed, so lets assume it is placed at the output.

 Now, consider that the connection between the tuner output and the
 windowsill is with 20 feet of RG-213.  The balanced line is connected
 directly to the coax (no balun).  By the analysis presented, the loss
 will be exactly the same as with the balun connected at the windowsill
 end of the coax.

 Both conditions are electrically the same (If that point is arguable,
 then the balun at the tuner input is just as arguable).

 If we can extend this argument, we would be able to conclude that it
 makes no difference on a coax fed antenna whether the balun is placed at
 the antenna or at the tuner output - no matter whether the feedline is
 coax or balanced line.  Oh, yes, both the coax or balanced line must be
 isolated and run with the same rules normally applied to balanced line.
 The point is that while theory says it makes no difference, it is
 impossible to achieve that perfect isolation, so the argument falls apart.

 Because most would not consider connecting a balanced line to coax
 without an intervening balun because we have been taught that we must
 preserve balance in order for things to be correct.
 The fallacy I see with the  balun at the input vs. balun at the output
 argument is that with the balun on the input, everything that follows
 must be perfectly isolated from ground - and that is difficult to
 achieve when all physical things are considered - if there are *any*
 strays, it defeats the principle of perfect isolation.  That is also
 what makes my example of the 20 feet of coax at the balanced output of a
 tuner not a practical consideration - one cannot easily achieve equal
 coupling of the center conductor and shield if there are any surrounding
 objects.  That fact makes the unbalanced tuner with an input balun not
 practical  because that perfect isolation is just as (or more) difficult
 and expensive to achieve than it would be to implement a balanced network.

 73,
 Don W3FPR


 On 12/12/2011 3:38 PM, Dean Straw wrote:
 While we're at it, let's look at the potential loss due to line
 losses at a CM choke balun placed in the wrong place in an antenna 
 system.
 Assume the common scenario where a balanced antenna is fed with open-wire
 transmission line to a 1:1 common-mode choke balun located at the shack
 window. From the balun at the window the ham uses, say, a 20-foot section 
 of
 RG-213 to the antenna tuner (which in this case is an unbalanced tuning
 network). Assume again that the CM choke balun uses three feet of RG-213
 wound on the appropriate ferrite donuts to achieve the target common-mode
 impedance of 5000 ohms so that common-mode currents are choked off 
 properly.

 The total length of RG-213 is now 23 feet. Again, we'll present the
 balun at the windowsill with a load of 3000 ohms. The overall
 differential

Re: [Elecraft] Balun at input or output of tuner

[Jim Brown]

On 12/12/2011 5:10 PM, Jim Brown wrote:
 Yes, chokes like these would be a great choice for use at the feedpoint
 of ANY HF antenna, whether fed with coax or parallel conductor line.

One VERY important exception that I forgot to mention is that common 
mode chokes can be destructively overheated by running high power into 
badly unbalanced antennas. Off-center fed antennas like Windoms can 
place VERY high common mode voltages across common mode chokes. The only 
solution I know of is to use multiple chokes in series on the feedline 
IMO, this sort of antenna is a poor choice in today's world, where local 
RF noise is made worse by pickup on the feedline.

A few years ago, I investigated this by  modeling the common mode 
voltage, and the resulting heat dissipation, in a common mode choke at 
the feedpoint of a 40M dipole whose feedpoint was moved off center in 
increments of 3 ft, at 1.5kW, fed by a half wavelength of coax (67 ft).  
At this worst case feedline length, you don't have to go very far off 
center to produce a lot of heat in the choke.  The results are 
summarized in a table in a Power Point for a presentation I've done for 
several ham clubs.  One of these bifilar chokes would be OK on a Windom 
at the 600W level produced by the KPA500, but could fail at max legal 
power. See page 43 of

http://audiosystemsgroup.com/CoaxChokesPPT.pdf

73, Jim Brown K9YC
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Re: [Elecraft] Balun at input or output of tuner

[Dean Straw]

Jim Brown said:
Mon, 12 Dec 2011 17:10:36 -0800
 
 I have not attempted to measure the Zo of the bifilar wound chokes I've 
 built using #12 and #14 THHN, but Jerry Sevick, in the last of his 
 books, did wind some using exactly that method and that wire, and he 
 says the Zo of those he wound were about 100 ohms. 

This is a useful data point. (I've got to rummage through my library to find
the Sevick book.) 

I used a bifilar wound CM choke at the input of the ARRL high-powered tuner
described in late editions of The ARRL Antenna Book. It had 12 bifilar
turns of #10 AWG Formvar wire on a 24-inch diameter OD Type 43 core.
(Nowadays I'd probably use a more optimal Type 31 mix.) In testing the input
balun (aka CM choke) 1500 W of RF at 29.7 MHz was applied for 60 seconds.
The #10 wire in the balun got warm to the touch (after the RF was shut off!)
but the core remained cool, as it should when there are no common-mode
currents, only differential-mode current in the bifilar-wound transmission
line.

Now, #10 wire is roughly the same size as the inner conductor used in
RG-213. On 10 meters the majority of loss in the bifilar transmission line
wound around the torroid will be I-squared-R conductor loss, rather than
additional dielectric losses that come into effect in the VHF and UHF
regions. So, I then assume that the matched-line loss in the bifilar-wound
transmission line is the same as that for RG-213 at HF so that I can do
computations using TLW. 

I then used the User-Defined Transmission Lines capability in TLW as
follows: Frequency = 28.0 MHz; Matched-Line Attenuation, dB/100 Feet =
1.142, Velocity Factor = 0.95; R0 = 100 ohms; Computed X0 = -0.698 ohms.
Again, a total length of three feet is assumed for the bifilar-wound
transmission line.

For a 3000 + j 0 load, TLW reports additional line loss due to SWR (which is
30:1) of 0.416 dB, a power loss in the balun  of 137.0 W for a 1500-W
transmitter. This level of dissipation in a physically small package will
result in catostrophic destruction when the balun is placed at the output of
the tuner.

For a 3 + j 0 ohm load, the SWR is 33.33:1, and the total line loss is 0.449
dB, amounting to 147.3 W dissipation in the balun -- again, this amount of
power in the CM choke balun would surely destroy it. The use a a
bifilar-wound transmission line instead of RG-213 has resulted in a slightly
greater susceptibility to catosphrophic destruction at low-impedance loads
when the balun is placed at the output of the tuner.

For a 5 + j 0 load (a 10:1 SWR), the total line loss is 0.274 dB, which for
1500 W is 91.7 W for 1500 W input, or 30.6 W for 500 W RF input. This would
be about the limit of safe operation for a CM choke balun placed at the
output terminals of an antenna tuner.

73, Dean, N6BV


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Re: [Elecraft] Balun at input or output of tuner

[Jim Brown]

On 12/13/2011 10:43 AM, Dean Straw wrote:
 I used a bifilar wound CM choke at the input of the ARRL high-powered tuner
 described in late editions of The ARRL Antenna Book. It had 12 bifilar
 turns of #10 AWG Formvar wire on a 24-inch diameter OD Type 43 core.

Jerry said that Zo for this sort of wire and winding style was about 50 
ohms.  I wound some that way, and they acted like they were close to 50 
ohms (as observed by SWR measurements) when inserted between TX and tuner.

73, Jim K9YC
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Re: [Elecraft] Balun at input or output of tuner

[Joe Subich, W4TV]

 I used a bifilar wound CM choke at the input of the ARRL
 high-powered tuner described in late editions of The ARRL Antenna
 Book. It had 12 bifilar turns of #10 AWG Formvar wire on a 24-inch
 diameter OD Type 43 core. (Nowadays I'd probably use a more optimal
 Type 31 mix.) In testing the input balun (aka CM choke) 1500 W of RF
 at 29.7 MHz was applied for 60 seconds. The #10 wire in the balun
 got warm to the touch (after the RF was shut off!) but the core
 remained cool, as it should when there are no common-mode currents,
 only differential-mode current in the bifilar-wound transmission
 line.

Moving this discussion away from the tuner and to the feedpoint of the
antenna ... I would never use a bifilar wound CM choke with a high HF
antenna.  Years ago I tried to use a well known, third party high power
balun on a triband antenna with a reputation for blowing its OEM
(fuse) balun.  That attempt was spectacularly unsuccessful on 15 meters
where the 90-100 Ohm Zo of the bifilar winding coupled with a line
length of slightly over 12 feet transformed the normally benign 50
Ohm SWR of the antenna into something that was poor across the entire
band.

With an antenna supporting more than three bands, it is likely that
the transformer effect would impact at least one band!

73,

... Joe, W4TV


On 12/13/2011 1:43 PM, Dean Straw wrote:

 Jim Brown said:
 Mon, 12 Dec 2011 17:10:36 -0800

 I have not attempted to measure the Zo of the bifilar wound chokes I've
 built using #12 and #14 THHN, but Jerry Sevick, in the last of his
 books, did wind some using exactly that method and that wire, and he
 says the Zo of those he wound were about 100 ohms.

 This is a useful data point. (I've got to rummage through my library to find
 the Sevick book.)

 I used a bifilar wound CM choke at the input of the ARRL high-powered tuner
 described in late editions of The ARRL Antenna Book. It had 12 bifilar
 turns of #10 AWG Formvar wire on a 24-inch diameter OD Type 43 core.
 (Nowadays I'd probably use a more optimal Type 31 mix.) In testing the input
 balun (aka CM choke) 1500 W of RF at 29.7 MHz was applied for 60 seconds.
 The #10 wire in the balun got warm to the touch (after the RF was shut off!)
 but the core remained cool, as it should when there are no common-mode
 currents, only differential-mode current in the bifilar-wound transmission
 line.

 Now, #10 wire is roughly the same size as the inner conductor used in
 RG-213. On 10 meters the majority of loss in the bifilar transmission line
 wound around the torroid will be I-squared-R conductor loss, rather than
 additional dielectric losses that come into effect in the VHF and UHF
 regions. So, I then assume that the matched-line loss in the bifilar-wound
 transmission line is the same as that for RG-213 at HF so that I can do
 computations using TLW.

 I then used the User-Defined Transmission Lines capability in TLW as
 follows: Frequency = 28.0 MHz; Matched-Line Attenuation, dB/100 Feet =
 1.142, Velocity Factor = 0.95; R0 = 100 ohms; Computed X0 = -0.698 ohms.
 Again, a total length of three feet is assumed for the bifilar-wound
 transmission line.

 For a 3000 + j 0 load, TLW reports additional line loss due to SWR (which is
 30:1) of 0.416 dB, a power loss in the balun  of 137.0 W for a 1500-W
 transmitter. This level of dissipation in a physically small package will
 result in catostrophic destruction when the balun is placed at the output of
 the tuner.

 For a 3 + j 0 ohm load, the SWR is 33.33:1, and the total line loss is 0.449
 dB, amounting to 147.3 W dissipation in the balun -- again, this amount of
 power in the CM choke balun would surely destroy it. The use a a
 bifilar-wound transmission line instead of RG-213 has resulted in a slightly
 greater susceptibility to catosphrophic destruction at low-impedance loads
 when the balun is placed at the output of the tuner.

 For a 5 + j 0 load (a 10:1 SWR), the total line loss is 0.274 dB, which for
 1500 W is 91.7 W for 1500 W input, or 30.6 W for 500 W RF input. This would
 be about the limit of safe operation for a CM choke balun placed at the
 output terminals of an antenna tuner.

 73, Dean, N6BV


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Re: [Elecraft] Balun at input or output of tuner

[Alan Bloom]

 Now, #10 wire is roughly the same size as the inner conductor used in
 RG-213. On 10 meters the majority of loss in the bifilar transmission
 line wound around the torroid will be I-squared-R conductor loss,
 rather than additional dielectric losses that come into effect in
 the VHF and UHF regions. So, I then assume that the matched-line
 loss in the bifilar-wound transmission line is the same as that for
 RG-213 at HF so that I can do computations using TLW. 

Is that a valid assumption?  I thought that much of the loss in coax is
due to the dielectric loss of the insulation.  That implies that the
bifilar winding should have less loss than coax.

Alan


On Tue, 2011-12-13 at 10:43 -0800, Dean Straw wrote:
 Jim Brown said:
 Mon, 12 Dec 2011 17:10:36 -0800
  
  I have not attempted to measure the Zo of the bifilar wound chokes I've 
  built using #12 and #14 THHN, but Jerry Sevick, in the last of his 
  books, did wind some using exactly that method and that wire, and he 
  says the Zo of those he wound were about 100 ohms. 
 
 This is a useful data point. (I've got to rummage through my library to find
 the Sevick book.) 
 
 I used a bifilar wound CM choke at the input of the ARRL high-powered tuner
 described in late editions of The ARRL Antenna Book. It had 12 bifilar
 turns of #10 AWG Formvar wire on a 24-inch diameter OD Type 43 core.
 (Nowadays I'd probably use a more optimal Type 31 mix.) In testing the input
 balun (aka CM choke) 1500 W of RF at 29.7 MHz was applied for 60 seconds.
 The #10 wire in the balun got warm to the touch (after the RF was shut off!)
 but the core remained cool, as it should when there are no common-mode
 currents, only differential-mode current in the bifilar-wound transmission
 line.
 
 Now, #10 wire is roughly the same size as the inner conductor used in
 RG-213. On 10 meters the majority of loss in the bifilar transmission line
 wound around the torroid will be I-squared-R conductor loss, rather than
 additional dielectric losses that come into effect in the VHF and UHF
 regions. So, I then assume that the matched-line loss in the bifilar-wound
 transmission line is the same as that for RG-213 at HF so that I can do
 computations using TLW. 
 
 I then used the User-Defined Transmission Lines capability in TLW as
 follows: Frequency = 28.0 MHz; Matched-Line Attenuation, dB/100 Feet =
 1.142, Velocity Factor = 0.95; R0 = 100 ohms; Computed X0 = -0.698 ohms.
 Again, a total length of three feet is assumed for the bifilar-wound
 transmission line.
 
 For a 3000 + j 0 load, TLW reports additional line loss due to SWR (which is
 30:1) of 0.416 dB, a power loss in the balun  of 137.0 W for a 1500-W
 transmitter. This level of dissipation in a physically small package will
 result in catostrophic destruction when the balun is placed at the output of
 the tuner.
 
 For a 3 + j 0 ohm load, the SWR is 33.33:1, and the total line loss is 0.449
 dB, amounting to 147.3 W dissipation in the balun -- again, this amount of
 power in the CM choke balun would surely destroy it. The use a a
 bifilar-wound transmission line instead of RG-213 has resulted in a slightly
 greater susceptibility to catosphrophic destruction at low-impedance loads
 when the balun is placed at the output of the tuner.
 
 For a 5 + j 0 load (a 10:1 SWR), the total line loss is 0.274 dB, which for
 1500 W is 91.7 W for 1500 W input, or 30.6 W for 500 W RF input. This would
 be about the limit of safe operation for a CM choke balun placed at the
 output terminals of an antenna tuner.
 
 73, Dean, N6BV
 
 
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Re: [Elecraft] Balun at input or output of tuner

[Dean Straw]

Joe:

Right on -- certain unnamed baluns had a quite reputation as being RF fuses.

But as the suject title above says, I'm still talking about the pros and
cons of placing a CM choke balun at the input or at the output of an
unbalancing antena tuner to feed balanced lines. Both positions are valid
ones, and like most engineering matters there are tradeoffs to both
approaches. Some tradeoffs involve significant smoke and flames... !

73, Dean, N6BV

-Original Message-
From: Joe Subich, W4TV [mailto:li...@subich.com] 
Sent: Tuesday, December 13, 2011 11:21 AM
To: Dean Straw
Cc: j...@audiosystemsgroup.com; elecraft@mailman.qth.net
Subject: Re: [Elecraft] Balun at input or output of tuner


 I used a bifilar wound CM choke at the input of the ARRL high-powered 
 tuner described in late editions of The ARRL Antenna Book. It had 12 
 bifilar turns of #10 AWG Formvar wire on a 24-inch diameter OD Type 43 
 core. (Nowadays I'd probably use a more optimal Type 31 mix.) In 
 testing the input balun (aka CM choke) 1500 W of RF at 29.7 MHz was 
 applied for 60 seconds. The #10 wire in the balun got warm to the 
 touch (after the RF was shut off!) but the core remained cool, as it 
 should when there are no common-mode currents, only differential-mode 
 current in the bifilar-wound transmission line.

Moving this discussion away from the tuner and to the feedpoint of the
antenna ... I would never use a bifilar wound CM choke with a high HF
antenna.  Years ago I tried to use a well known, third party high power
balun on a triband antenna with a reputation for blowing its OEM
(fuse) balun.  That attempt was spectacularly unsuccessful on 15 meters
where the 90-100 Ohm Zo of the bifilar winding coupled with a line length
of slightly over 12 feet transformed the normally benign 50 Ohm SWR of the
antenna into something that was poor across the entire band.

With an antenna supporting more than three bands, it is likely that the
transformer effect would impact at least one band!

73,

... Joe, W4TV


On 12/13/2011 1:43 PM, Dean Straw wrote:

 Jim Brown said:
 Mon, 12 Dec 2011 17:10:36 -0800

 I have not attempted to measure the Zo of the bifilar wound chokes 
 I've built using #12 and #14 THHN, but Jerry Sevick, in the last of 
 his books, did wind some using exactly that method and that wire, and 
 he says the Zo of those he wound were about 100 ohms.

 This is a useful data point. (I've got to rummage through my library 
 to find the Sevick book.)

 I used a bifilar wound CM choke at the input of the ARRL high-powered 
 tuner described in late editions of The ARRL Antenna Book. It had 12 
 bifilar turns of #10 AWG Formvar wire on a 24-inch diameter OD Type 43
core.
 (Nowadays I'd probably use a more optimal Type 31 mix.) In testing the 
 input balun (aka CM choke) 1500 W of RF at 29.7 MHz was applied for 60
seconds.
 The #10 wire in the balun got warm to the touch (after the RF was shut 
 off!) but the core remained cool, as it should when there are no 
 common-mode currents, only differential-mode current in the 
 bifilar-wound transmission line.

 Now, #10 wire is roughly the same size as the inner conductor used in 
 RG-213. On 10 meters the majority of loss in the bifilar transmission 
 line wound around the torroid will be I-squared-R conductor loss, 
 rather than additional dielectric losses that come into effect in the 
 VHF and UHF regions. So, I then assume that the matched-line loss in 
 the bifilar-wound transmission line is the same as that for RG-213 at 
 HF so that I can do computations using TLW.

 I then used the User-Defined Transmission Lines capability in TLW as
 follows: Frequency = 28.0 MHz; Matched-Line Attenuation, dB/100 Feet = 
 1.142, Velocity Factor = 0.95; R0 = 100 ohms; Computed X0 = -0.698 ohms.
 Again, a total length of three feet is assumed for the bifilar-wound 
 transmission line.

 For a 3000 + j 0 load, TLW reports additional line loss due to SWR 
 (which is
 30:1) of 0.416 dB, a power loss in the balun  of 137.0 W for a 1500-W 
 transmitter. This level of dissipation in a physically small package 
 will result in catostrophic destruction when the balun is placed at 
 the output of the tuner.

 For a 3 + j 0 ohm load, the SWR is 33.33:1, and the total line loss is 
 0.449 dB, amounting to 147.3 W dissipation in the balun -- again, this 
 amount of power in the CM choke balun would surely destroy it. The use 
 a a bifilar-wound transmission line instead of RG-213 has resulted in 
 a slightly greater susceptibility to catosphrophic destruction at 
 low-impedance loads when the balun is placed at the output of the tuner.

 For a 5 + j 0 load (a 10:1 SWR), the total line loss is 0.274 dB, 
 which for
 1500 W is 91.7 W for 1500 W input, or 30.6 W for 500 W RF input. This 
 would be about the limit of safe operation for a CM choke balun placed 
 at the output terminals of an antenna tuner.

 73, Dean, N6BV


 __
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Re: [Elecraft] Balun at input or output of tuner

[David Herring]

Aloha Jim, Joe, Alan, Dean and the rest of the reflector,

I'm thoroughly enjoying reading this thread.

I'd like to ask a few questions.

Mine is a 100 watt station, but with aspirations of getting a KPA-500 
eventually. I have a Palstar BT1500A Balanced L Antenna Tuner feeding a 
vertical dipole fed with 450 window line.  The antenna is crafted from one 
continuous length of window line, the dipole being formed by splitting the last 
30-some-odd feet of the window line and attaching it to a 40 foot fiberglass 
pole. This antenna is used only for 30 meters and higher. I believe Palstar 
puts their balun at the input of this tuner.  I have a fairly small amount of 
RF in the shack.

I read one of you advocate the use of a CM choke at the feed point of an 
antenna, even if it's being fed with a balanced feed line.  I had never 
considered that, so the notion of a cm choke with a balanced feed line is a new 
one to me (but seems logical enough). If I understand correctly, that will 
minimize common mode currents on the feed line, just as it would with coax, and 
that may very well help to minimize the little bit of RF in the shack I seem to 
have.

Then there was discussion of placing one at the output of the tuner, but then I 
read about the one at the tuner output being heat stressed and prone to fail ( 
? )  

My initial thought was if I'm guarding from common mode currents, maybe one 
would want to put a CM choke at both the feed point and the tuner output.

My questions are basically these:  would it be advisable to use CM chokes at 
both positions? (for me, the one at the tuner output would likely be outside, 
thus electrically 5 feet from the physical tuner)  What about the heat 
dissipation and stress on the tuner output side CM choke - it sounds like a 
show stopper to me but maybe you can provide some perspective on this?  If in 
this case only one cm choke is necessary or recommended, are we able to come to 
some consensus as to which position is best, at least in general?

Again, I'm thoroughly enjoying this thread and thanks a lot for sharing this 
with us.

73  Aloha,

Dave
AH6TD


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Re: [Elecraft] Balun at input or output of tuner

[Guy Olinger K2AV]

Jerry Sevick used a monster T400A-2 toroid, #2 powdered iron, 4 inches in
diameter, intended to be the 4:1 up transformation for the back of high
power tuners. (Sevick, Understanding Baluns 2003, CQ Communications, pp
60-61)  I have run these some times with brick-on-key 1500 watts and never
managed to get heat.  I've never personally managed to construct anything
that would stress one of these.

I'm currently using a 17 turn trifilar winding on a T400A-2 as a 4:1
isolation transformer (not a balun, no direct connection between primary
and secondary) feeding the 90 ohm base of my 160m 3/8 wave inverted L plus
folded counterpoise to 360 ohm 450 window line (Wireman #554).
 Particularly with the significant capacitive reactance of the
counterpoise, I was definitely expecting this would put some serious heat
on the core QRO, and maybe invalidate the concept, but I have gone 15 min
QRO BOK, immediately walked out to the base, and the core was stone cold.
 The whole thing seemed cold. There was a little bit of condensation
visible inside the teflon tubing beforehand, and the BOK did not cause it
to evaporate.  I really don't know why it didn't heat up, but I'll take it.
 Thing is a killer ant.

So I'm thinking if you put up Jerry's 20 turn bifilar on a T400A2 as a
Ruthroff balun and slap it on the back of a tuner, that you're going to be
very hard pressed to warm it up with ordinary stuff.

73, Guy.

On Tue, Dec 13, 2011 at 1:43 PM, Dean Straw n...@arrl.net wrote:


 Jim Brown said:
 Mon, 12 Dec 2011 17:10:36 -0800

  I have not attempted to measure the Zo of the bifilar wound chokes I've
  built using #12 and #14 THHN, but Jerry Sevick, in the last of his
  books, did wind some using exactly that method and that wire, and he
  says the Zo of those he wound were about 100 ohms.

 This is a useful data point. (I've got to rummage through my library to
 find
 the Sevick book.)

 I used a bifilar wound CM choke at the input of the ARRL high-powered tuner
 described in late editions of The ARRL Antenna Book. It had 12 bifilar
 turns of #10 AWG Formvar wire on a 24-inch diameter OD Type 43 core.
 (Nowadays I'd probably use a more optimal Type 31 mix.) In testing the
 input
 balun (aka CM choke) 1500 W of RF at 29.7 MHz was applied for 60 seconds.
 The #10 wire in the balun got warm to the touch (after the RF was shut
 off!)
 but the core remained cool, as it should when there are no common-mode
 currents, only differential-mode current in the bifilar-wound transmission
 line.

 Now, #10 wire is roughly the same size as the inner conductor used in
 RG-213. On 10 meters the majority of loss in the bifilar transmission line
 wound around the torroid will be I-squared-R conductor loss, rather than
 additional dielectric losses that come into effect in the VHF and UHF
 regions. So, I then assume that the matched-line loss in the bifilar-wound
 transmission line is the same as that for RG-213 at HF so that I can do
 computations using TLW.

 I then used the User-Defined Transmission Lines capability in TLW as
 follows: Frequency = 28.0 MHz; Matched-Line Attenuation, dB/100 Feet =
 1.142, Velocity Factor = 0.95; R0 = 100 ohms; Computed X0 = -0.698 ohms.
 Again, a total length of three feet is assumed for the bifilar-wound
 transmission line.

 For a 3000 + j 0 load, TLW reports additional line loss due to SWR (which
 is
 30:1) of 0.416 dB, a power loss in the balun  of 137.0 W for a 1500-W
 transmitter. This level of dissipation in a physically small package will
 result in catostrophic destruction when the balun is placed at the output
 of
 the tuner.

 For a 3 + j 0 ohm load, the SWR is 33.33:1, and the total line loss is
 0.449
 dB, amounting to 147.3 W dissipation in the balun -- again, this amount of
 power in the CM choke balun would surely destroy it. The use a a
 bifilar-wound transmission line instead of RG-213 has resulted in a
 slightly
 greater susceptibility to catosphrophic destruction at low-impedance loads
 when the balun is placed at the output of the tuner.

 For a 5 + j 0 load (a 10:1 SWR), the total line loss is 0.274 dB, which for
 1500 W is 91.7 W for 1500 W input, or 30.6 W for 500 W RF input. This would
 be about the limit of safe operation for a CM choke balun placed at the
 output terminals of an antenna tuner.

 73, Dean, N6BV


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Re: [Elecraft] Balun at input or output of tuner

[Jim Brown]

On 12/13/2011 11:48 AM, Alan Bloom wrote:
 Is that a valid assumption?  I thought that much of the loss in coax is
 due to the dielectric loss of the insulation.  That implies that the
 bifilar winding should have less loss than coax.

This is a very common misconception, and it is VERY wrong below UHF for 
nearly all practical transmission lines that aren't defective (for 
example, a wet dielectric). If you do the math, you see that below UHF, 
the loss is virtually ALL due to copper (taking skin effect into account 
for both conductors).  There's an excellent paper by Frank Witt in one 
of the ARRL Antenna Compendiums (which Dean also edited) showing that 
window line exhibits significant dielectric loss at HF when it gets wet.

You can see the equation for coax on datasheets for Times LMR coax types 
on their website, with the equation for each cable type reflecting the 
physical constants for that particular cable. There are two terms, one 
for copper loss, the other for dielectric loss. Measured data for a few 
cables that I've measured track those computed curves, and if you put 
them into a spreadsheet and plot the two terms vs frequency, you can 
clearly see which terms are contributing.  I suspect that they are also 
used in Dean's TLW program. Right, Dean?

73, Jim K9YC
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Re: [Elecraft] Balun at input or output of tuner

[Ian White GM3SEK]

Jim Brown wrote:
On 12/13/2011 11:48 AM, Alan Bloom wrote:
 Is that a valid assumption?  I thought that much of the loss in coax is
 due to the dielectric loss of the insulation.  That implies that the
 bifilar winding should have less loss than coax.

This is a very common misconception, and it is VERY wrong below UHF for
nearly all practical transmission lines that aren't defective (for
example, a wet dielectric). If you do the math, you see that below UHF,
the loss is virtually ALL due to copper (taking skin effect into account
for both conductors).

Much of the confusion arises from the advertising for newer types of 
coax that have lower loss than a similar solid PE equivalent. The 
improvement is touted as being due to low loss foam dielectric when 
that simply isn't true.

The reduction in loss is almost entirely due to increase in the diameter 
of the center conductor (because that conductor has the largest current 
density and hence the highest skin effect losses). The foam dielectric 
is merely something that *has* to be used to compensate for the thicker 
center conductor, in order to keep the same characteristic impedance.

In all the coaxial cables we know in amateur radio, dielectric losses 
only begin to become important at frequencies above 1GHz.


-- 

73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek
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Re: [Elecraft] Balun at input or output of tuner

[Ron D'Eau Claire]

I used to think that dielectric losses were a significant factor until
someone pointed out the attenuation data for various transmission lines
between 2 and 500 MHz. The plots for all the various transmission lines are
straight lines. If dielectric losses were involved, they should curve toward
the higher frequencies.

When I feed a doublet with open wire line for all-band operation with a
tuner, I use the largest conductors practicable to minimize copper losses,
especially at current loops. 

Another factor is the impedance the feed line sees at the radiator. Most
open wire line has an impedance of somewhere between 300 to 600 ohms. It the
radiator is at least 1/2 wavelength long, the impedance at the feed point
will range from about 50 ohms at 1/2 wavelength to perhaps 3500 ohms when
the radiator is 1 wavelength total. With 50 ohm line that represents a ratio
of 1:1 to 70:1. Using open wire line at, say, 450 ohms nominal, the ratio is
only between 8:1 and 9:1.  

Ron AC7AC 

-Original Message-
Jim Brown wrote:
On 12/13/2011 11:48 AM, Alan Bloom wrote:
 Is that a valid assumption?  I thought that much of the loss in coax is
 due to the dielectric loss of the insulation.  That implies that the
 bifilar winding should have less loss than coax.

This is a very common misconception, and it is VERY wrong below UHF for
nearly all practical transmission lines that aren't defective (for
example, a wet dielectric). If you do the math, you see that below UHF,
the loss is virtually ALL due to copper (taking skin effect into account
for both conductors).

Much of the confusion arises from the advertising for newer types of 
coax that have lower loss than a similar solid PE equivalent. The 
improvement is touted as being due to low loss foam dielectric when 
that simply isn't true.

The reduction in loss is almost entirely due to increase in the diameter 
of the center conductor (because that conductor has the largest current 
density and hence the highest skin effect losses). The foam dielectric 
is merely something that *has* to be used to compensate for the thicker 
center conductor, in order to keep the same characteristic impedance.

In all the coaxial cables we know in amateur radio, dielectric losses 
only begin to become important at frequencies above 1GHz.


-- 

73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek
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Re: [Elecraft] Balun at input or output of tuner

[Jim Brown]

On 12/13/2011 2:47 PM, Ian White GM3SEK wrote:
 The reduction in loss is almost entirely due to increase in the diameter
 of the center conductor (because that conductor has the largest current
 density and hence the highest skin effect losses). The foam dielectric
 is merely something that*has*  to be used to compensate for the thicker
 center conductor, in order to keep the same characteristic impedance.

Exactly!

Jim
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