Re: [Elecraft] OT: Feedline Question

[Wes Stewart]

Yes, just like the bio (https://qrz.com/db/N7WS) says; been here 70 years.  I 
like to say I was conceived here, since my parents met and married in Tucson, 
but were actually in San Diego when I was born.  They moved back when I was a 
young child and I've never left.  No reason to, unless I want a chip shot to 
SV/A, instead of, 
I'll-never-live-long-enough-to-work-this-guy-through-the-east-coast.


Wes, N7WS, ex KN7CVT, K7CVT



.On 4/18/2017 1:24 PM, Phil Wheeler wrote:

Hey, and it looks like you are really in 7-land, Wes!

OTOH, I'm the "real W7OX", live in a suburb of Los Angeles and have not lived 
in 7-land (OR/WA) since 1960; farthest North was Palo Alto when I was at 
Stanford 1963-65.  But 20 years ago we considered retiring to Portland very 
seriously, so I used the Gates to get back my original call -- W7UOX -- and 
then shorten it to W7OX.


I like having the call for old times sake. But I do wish the prefixes had call 
area geographic meaning as they did in olden days.


73, Phil W7OX 


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Re: [Elecraft] OT: Feedline Question

[Phil Wheeler]

Hey, and it looks like you are really in 7-land, Wes!

OTOH, I'm the "real W7OX", live in a suburb of Los 
Angeles and have not lived in 7-land (OR/WA) since 
1960; farthest North was Palo Alto when I was at 
Stanford 1963-65.  But 20 years ago we considered 
retiring to Portland very seriously, so I used the 
Gates to get back my original call -- W7UOX -- and 
then shorten it to W7OX.


I like having the call for old times sake. But I 
do wish the prefixes had call area geographic 
meaning as they did in olden days.


73, Phil W7OX

On 4/18/17 12:57 PM, Wes Stewart wrote:
I'm cursed.  It's bad enough that I've worked (I 
thought) several stations in DX pileups only to 
later have the DX say, "Nope, we worked N6WS, 
not N7WS".  Now my work is attributed to him 
too.  (Just kidding Jim)


Actually, the article never appeared in QST.  
Too technical; it went right to the Antenna 
Compendium.  And as a caveat, I never intended 
the "wet" numbers to take on mythical 
properties.  Water most definitely negatively 
affects ladder lines (or as our European friends 
say, "chicken ladder line") but it's really 
really difficult to quantify with precision.


I never did get around to testing the piece of 
Wireman line that my friend Danny, K6MHE, sent 
me that was covered in moss. Living among 
Redwood trees is considerably different from 
living among Saguaro Cactii.


Wes, the real N7WS

 On 4/18/2017 10:37 AM, Jim Brown wrote:

On Tue,4/18/2017 10:10 AM, Guy Olinger K2AV wrote:
Then there is the loss based on number of 
spacers and loss tangent of the spacer 
material modifying the lesser air loss.


Below UHF, loss in transmission line is 
virtually all due to copper losses unless the 
dielectric material is wet or is otherwise made 
conductive.


Quite a few years ago, N6WS did some excellent 
work showing that losses in window line are 
greatly increased when it is wet. His work was 
published in QST and later included in Antenna 
Compendium #6. It should be required reading 
for anyone considering window line. He measured 
four types of window line and some open wire 
line he built himself. Putting some numbers to 
it, Wes's measurements showed loss at 50 MHz 
increased from about 0.4 dB/100 ft to more 
almost 6 dB/100 ft when it was wet. The open 
wire line showed no increased loss when wet.


73, Jim K9YC


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Re: [Elecraft] OT: Feedline Question

[Wes Stewart]

I'm cursed.  It's bad enough that I've worked (I thought) several stations in DX 
pileups only to later have the DX say, "Nope, we worked N6WS, not N7WS".  Now my 
work is attributed to him too.  (Just kidding Jim)


Actually, the article never appeared in QST.  Too technical; it went right to 
the Antenna Compendium.  And as a caveat, I never intended the "wet" numbers to 
take on mythical properties.  Water most definitely negatively affects ladder 
lines (or as our European friends say, "chicken ladder line") but it's really 
really difficult to quantify with precision.


I never did get around to testing the piece of Wireman line that my friend 
Danny, K6MHE, sent me that was covered in moss. Living among Redwood trees is 
considerably different from living among Saguaro Cactii.


Wes, the real N7WS

 On 4/18/2017 10:37 AM, Jim Brown wrote:

On Tue,4/18/2017 10:10 AM, Guy Olinger K2AV wrote:
Then there is the loss based on number of spacers and loss tangent of the 
spacer material modifying the lesser air loss.


Below UHF, loss in transmission line is virtually all due to copper losses 
unless the dielectric material is wet or is otherwise made conductive.


Quite a few years ago, N6WS did some excellent work showing that losses in 
window line are greatly increased when it is wet. His work was published in 
QST and later included in Antenna Compendium #6. It should be required reading 
for anyone considering window line. He measured four types of window line and 
some open wire line he built himself. Putting some numbers to it, Wes's 
measurements showed loss at 50 MHz increased from about 0.4 dB/100 ft to more 
almost 6 dB/100 ft when it was wet. The open wire line showed no increased 
loss when wet.


73, Jim K9YC 


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Re: [Elecraft] OT: Feedline Question

[Brian D]

What difference does oxidisation make on bare wire, ot tinning?? My feeders
are mainly enamelled copper which won't corrode. Does the enamel make a
significant difference? Hs anyone done the comparisons?




Guy Olinger K2AV  wrote:

> What you appear to refer to by "open wire line" is BARE wire with small
> spacers widely separated. Performance changes a lot if the "open wire
> line" is constructed with unstripped THHN. Particularly with surface
> tension on new THHN. Where hung on the level in a misting rain, I have
> seen a droplet per centimeter hanging on THHN insulation. Along with a
> rather large variation in Z as seen in the shack.


-- 
Brian Duffell   YarmEngland
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Re: [Elecraft] OT: Feedline Question

[Jim Brown]

On Tue,4/18/2017 11:26 AM, Guy Olinger K2AV wrote:
What you appear to refer to by "open wire line" is BARE wire with 
small spacers widely separated. 


That's what Wes built to compare with the window line. Most practical 
implementations of open wire line use much wider spacing. The increased 
loss that Wes measured was due to water on the un-windowed parts of the 
window line -- in other words, a significant fraction of the dielectric 
between the conductors was water. That would not be true of widely 
spaced wire, insulated or not.


73, Jim

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Re: [Elecraft] OT: Feedline Question

[Guy Olinger K2AV]

Hi, Jim,

What you appear to refer to by "open wire line" is BARE wire with small
spacers widely separated. Performance changes a lot if the "open wire line"
is constructed with unstripped THHN. Particularly with surface tension on
new THHN. Where hung on the level in a misting rain, I have seen a droplet
per centimeter hanging on THHN insulation. Along with a rather large
variation in Z as seen in the shack.

Just one more reason to keep to bare wire. Bare wire sloughs rain.

I remember 300 ohm TV open wire line from bare #18 copperweld with molded
spacers every three inches.

The 300 ohm ladder line if run near a furnace or fireplace flue would "go
bad" on TV channel 2 as well as the UHF channels. There was also this
phenomenon called acid rain which could severely modify electrical
behavior, including etching the copper conductors.

With the PE formed 300 ohm line, the reduction in signal strength could be
blamed on "the rain", which was true in one sense. But since it got better
when it dried up, the PE supported balanced line would never get the blame.

73, Guy K2AV



On Tue, Apr 18, 2017 at 1:37 PM, Jim Brown 
wrote:

> On Tue,4/18/2017 10:10 AM, Guy Olinger K2AV wrote:
>
>> Then there is the loss based on number of spacers and loss tangent of the
>> spacer material modifying the lesser air loss.
>>
>
> Below UHF, loss in transmission line is virtually all due to copper losses
> unless the dielectric material is wet or is otherwise made conductive.
>
> Quite a few years ago, N6WS did some excellent work showing that losses in
> window line are greatly increased when it is wet. His work was published in
> QST and later included in Antenna Compendium #6. It should be required
> reading for anyone considering window line. He measured four types of
> window line and some open wire line he built himself. Putting some numbers
> to it, Wes's measurements showed loss at 50 MHz increased from about 0.4
> dB/100 ft to more almost 6 dB/100 ft when it was wet. The open wire line
> showed no increased loss when wet.
>
> 73, Jim K9YC
>
>
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Re: [Elecraft] OT; Feedline question

[Clay Autery]

And your effort is most sincerely appreciated.  :)

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On 4/17/2017 10:31 PM, Al Lorona wrote:
> This obsessive exercise on my part illustrates that spacers don't make a 
> whole lot of difference, but they do make a difference. You may want to 
> include their effect or not.

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Re: [Elecraft] OT: Feedline Question

[Jim Brown]

On Tue,4/18/2017 10:10 AM, Guy Olinger K2AV wrote:

Then there is the loss based on number of spacers and loss tangent of the 
spacer material modifying the lesser air loss.


Below UHF, loss in transmission line is virtually all due to copper 
losses unless the dielectric material is wet or is otherwise made 
conductive.


Quite a few years ago, N6WS did some excellent work showing that losses 
in window line are greatly increased when it is wet. His work was 
published in QST and later included in Antenna Compendium #6. It should 
be required reading for anyone considering window line. He measured four 
types of window line and some open wire line he built himself. Putting 
some numbers to it, Wes's measurements showed loss at 50 MHz increased 
from about 0.4 dB/100 ft to more almost 6 dB/100 ft when it was wet. The 
open wire line showed no increased loss when wet.


73, Jim K9YC

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Re: [Elecraft] OT: Feedline Question

[Guy Olinger K2AV]

The effect of spacers is a very complex equation. One large modifier to the
end result is the number of spacers per unit of length. Then there is the
issue that the relative permittivity in between spacers reverts to air away
from the spacer. Then there is the area on either side of a spacer where
the effective permittivity blends from that of the spacer to that of air.

Then there is the loss based on number of spacers and loss tangent of the
spacer material modifying the lesser air loss.

Beyond that there is this peculiar ham inclination to use indoor insulated
electrical wire (THHN - rated dry indoors inside conduit only, 600 volts at
60 Hz) for QRO outdoor RF purposes. E.g.
https://www.73cnc.com/product_p/ls31.htm

Figure the wildly variant composition of PVC insulation at manufacture
followed by years of deteriorating UV outdoors.

In the end it is far easier to construct a feedline with a scientific guess
to obtain a target Z zero and then measure and adjust design to hit it on
the head and/or reduce its loss.

In practice there is little difference between 400 and 450 that is not
soaked up by all the tuner or circuitry finaglement we must engage in to
convert a wild range of Z to the narrow, narrow range actually tolerated by
our transistor finals.

Wireman for years has been selling various window lines we all
euphemistically call "450 ohm" which in fact vary between 360 and 440 ohm Z
zero. The reason for the variance is the spacing on all those lines is
identical regardless of the variation in wire diameter.

The constant wire diameter reduces the manufacturing setup and run costs
passed on to a cheep penny pinching ham population. [I include myself as
afflicted by this penny-pinching malaise. I just try to keep this nearly
irresistible inclination from dragging me into stupidity, as it has already
done on some number of occasions.]

73, Guy K2AV


On Tue, Apr 18, 2017 at 11:00 AM, k...@juno.com <k...@juno.com> wrote:

>
>
> Message: 4
> Date: Tue, 18 Apr 2017 03:31:59 + (UTC)
> From: Al Lorona <alor...@sbcglobal.net>
> To: "elecraft@mailman.qth.net" <elecraft@mailman.qth.net>
> Subject: Re: [Elecraft] OT; Feedline question
> Message-ID: <852881305.2998918.1492486319...@mail.yahoo.com>
> Content-Type: text/plain; charset=UTF-8
>
> If instead of using the relative permittivity of air, 1.00059, for
> calculations of open-wire line, you use the effective permittivity
> including any spacers used to homebrew the line, this value will increase
> slightly.
>
>
>
> For instance, I am using spacers made of a material called "nylon 6,6 30%
> glass fiber-reinforced" which happens to have a relative permittivity of
> 3.9. This has the effect of increasing the effective permittivity between
> the wires from 1.00059 to 1.08656. Another way of saying this is that the
> velocity factor goes from 1 (for pure air) to 0.959, or about 96% with the
> spacers. The effect of this is to make the characteristic impedance of the
> line drop from around 480 to around 460 ohms.
>
> ( See http://www.emclab.cei.uec.ac.jp/xiao/Wire/index.html )
>
> This obsessive exercise on my part illustrates that spacers don't make a
> whole lot of difference, but they do make a difference. You may want to
> include their effect or not.
>
> Al  W6LX OM Al, Thank you for taking the time to share your results on
> this forum.
> "That which is not rigorous is meaningless."...Attributed to Blaise
> Pascal The results may not be significant or even of minor interest to
> many, but how would we know had this work not be done and presented here.
> 72, Tim Colbert  K3HX
> 
> "Better Than Adderall" Pill Now Legal For Your State Residents
> Health Tips Daily
> http://thirdpartyoffers.juno.com/TGL3131/58f62a48922102a474f94st04duc
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[Elecraft] OT: Feedline Question

[k...@juno.com]

Message: 4
Date: Tue, 18 Apr 2017 03:31:59 + (UTC)
From: Al Lorona <alor...@sbcglobal.net>
To: "elecraft@mailman.qth.net" <elecraft@mailman.qth.net>
Subject: Re: [Elecraft] OT; Feedline question
Message-ID: <852881305.2998918.1492486319...@mail.yahoo.com>
Content-Type: text/plain; charset=UTF-8

If instead of using the relative permittivity of air, 1.00059, for calculations 
of open-wire line, you use the effective permittivity including any spacers 
used to homebrew the line, this value will increase slightly. 



For instance, I am using spacers made of a material called "nylon 6,6 30% glass 
fiber-reinforced" which happens to have a relative permittivity of 3.9. This 
has the effect of increasing the effective permittivity between the wires from 
1.00059 to 1.08656. Another way of saying this is that the velocity factor goes 
from 1 (for pure air) to 0.959, or about 96% with the spacers. The effect of 
this is to make the characteristic impedance of the line drop from around 480 
to around 460 ohms. 

( See http://www.emclab.cei.uec.ac.jp/xiao/Wire/index.html )

This obsessive exercise on my part illustrates that spacers don't make a whole 
lot of difference, but they do make a difference. You may want to include their 
effect or not.

Al  W6LX OM Al, Thank you for taking the time to share your results on this 
forum.
"That which is not rigorous is meaningless."...Attributed to Blaise Pascal 
The results may not be significant or even of minor interest to many, but how 
would we know had this work not be done and presented here. 72, Tim Colbert  
K3HX

"Better Than Adderall" Pill Now Legal For Your State Residents
Health Tips Daily
http://thirdpartyoffers.juno.com/TGL3131/58f62a48922102a474f94st04duc
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Re: [Elecraft] OT; Feedline question

[Al Lorona]

If instead of using the relative permittivity of air, 1.00059, for calculations 
of open-wire line, you use the effective permittivity including any spacers 
used to homebrew the line, this value will increase slightly. 



For instance, I am using spacers made of a material called "nylon 6,6 30% glass 
fiber-reinforced" which happens to have a relative permittivity of 3.9. This 
has the effect of increasing the effective permittivity between the wires from 
1.00059 to 1.08656. Another way of saying this is that the velocity factor goes 
from 1 (for pure air) to 0.959, or about 96% with the spacers. The effect of 
this is to make the characteristic impedance of the line drop from around 480 
to around 460 ohms. 

( See http://www.emclab.cei.uec.ac.jp/xiao/Wire/index.html )

This obsessive exercise on my part illustrates that spacers don't make a whole 
lot of difference, but they do make a difference. You may want to include their 
effect or not.

Al  W6LX
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Re: [Elecraft] OT; Feedline question

[Wes Stewart]

I'll agree with both points.

That said, think about the space between wires.  On and about the wires is a 
relatively thin layer of plastic.  From there, the space between wires is filled 
with...wait for it...air.


It might be worthwhile to read this: http://k6mhe.com/n7ws/Ladder_Line.pdf

On 4/15/2017 6:16 PM, Clay Autery wrote:

Actually thermoplastics are NOT majority air  I'm not an expert
here,


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Re: [Elecraft] OT; Feedline question

[Clay Autery]

Actually thermoplastics are NOT majority air  I'm not an expert
here, but the dielectric constant appears to increase with thickness and
probably with density of the material.

Keep in mind that the standard insulation on THHN is 0.015"
thermoplastic (PVC) and that is covered by a 3-4 mill layer of clear
nylon to protect the insulation on conduit pulls...

I've given up trying to understand it all fully

I've just decided to treat the entire feedline assembly from tuner
(radio) to antenna as a impedance matching network
Bottom line  getting the impedances in band to such a level that you
can tune it...

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MONTAC Enterprises
(318) 518-1389

On 4/15/2017 8:02 PM, Wes Stewart wrote:
> Why do you suppose a little bit of dielectric on the wire would make a
> huge change, when the majority of dielectric is still air?
>
>
> On 4/15/2017 3:56 PM, Clay Autery wrote:
>> Thanks
>>
>> So, these numbers are for BARE copper, right?
>> Using insulated wire changes things a bunch
>>
>> For instance 18 GA THHN/THWN has an approx. dc of 2.35, XLPE has a dc of
>> 5 or so  As the dielectric constant gets larger, things get real
>> fast.
>>
>> 18 GA THHN/THWN...  (dc = 2.35 approx.)
>>
>> To get the same 464 Ohms, the Center to center distance must increase to
>> 7.52 inches or so...
>
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Re: [Elecraft] OT; Feedline question

[Wes Stewart]

Why do you suppose a little bit of dielectric on the wire would make a huge 
change, when the majority of dielectric is still air?



On 4/15/2017 3:56 PM, Clay Autery wrote:

Thanks

So, these numbers are for BARE copper, right?
Using insulated wire changes things a bunch

For instance 18 GA THHN/THWN has an approx. dc of 2.35, XLPE has a dc of
5 or so  As the dielectric constant gets larger, things get real
fast.

18 GA THHN/THWN...  (dc = 2.35 approx.)

To get the same 464 Ohms, the Center to center distance must increase to
7.52 inches or so...


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Re: [Elecraft] OT; Feedline question

[Matt Zilmer]

I don't think you're missing anything.  It was a good question.  Please 
also see Clay's reply.


73,

matt W6NIA


On 4/15/2017 4:08 PM, Richard Fjeld wrote:

Okay, and thanks to all for the info which I will save.

What made me curious is that twin lead is stated in steps of 150 ohms.
IE. 300, 450, 600.
I assumed it was to match the impedance of certain antennas such as a
folded dipole, etc.
Since I understand my loop to be a non-resonant antenna, and using a
manual tuner, I thought
I'd be okay to change the spacer dims, but I wondered if I was
over-looking something.

Thanks again,

Dick, n0ce



On 4/15/2017 11:39 AM, Richard Fjeld wrote:

Forgive me for the OT, but there are many antenna people here above my
pay-grade.

I need to replace the spacers on my ladder line.  If I deviate from the
standard spacer length for impedance
(separation between conductors), are there problems I'm not thinking
of?  I use a quality manual tuner, and
an 80 meter delta loop.

Perhaps it would be best to reply off line for this.  Thank you in advance.

Dick, n0ce



--
"A delay is better than a disaster."
-- unknonwn

Matt Zilmer, W6NIA
[Shiraz]

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Re: [Elecraft] OT; Feedline question

[Matt Zilmer]

I was trying to find the dielectric constant (Epsilon sub r) for this 
poly jacket that's used on the standard HRO-available line.  The 
calculations I did were for open wire line with air being the dialectric 
(something like 1.0054).  The first ladder line that I used was made 
from BIC pens, cut in half for about 3" center to center. After that 
much hassle to put together and raise, when it got wind-blown and torn 
up, I just started using the HRO stuff.


Have only seen really heavy feeds in use at SW BC stations, and only 
twice at that. Looked like 4 AWG, but might've been heavier.  Some of 
WWVH's curtain feeds lookmuch the same.



73,

matt W6NIA


On 4/15/2017 3:56 PM, Clay Autery wrote:

Thanks

So, these numbers are for BARE copper, right?
Using insulated wire changes things a bunch

For instance 18 GA THHN/THWN has an approx. dc of 2.35, XLPE has a dc of
5 or so  As the dielectric constant gets larger, things get real
fast.

18 GA THHN/THWN...  (dc = 2.35 approx.)

To get the same 464 Ohms, the Center to center distance must increase to
7.52 inches or so...
The impedance with the quoted 1, 2, and 3 inch "D":

1" = 305-306 Ohms

2" = 359-360 Ohms

3" = 391-392 Ohms

I use 300 Ohm, 18 GA copper twin-lead with foam over wires and some hard
plastic over that  It's close to true 300 Ohm...

I'll have to go calculate the min size safe against various power
levels...  The separation distances get big fast with increase in the
conductor diameter, too.

73,

PS - there is an argument to be made for NOT using bare wire  if
anything MIGHT touch the feedline...   and wet wire   wet wire
changes performance a lot...  built with insulated wire, the changes are
MUCH smaller with wet wire...

__
Clay Autery, KY5G
MONTAC Enterprises
(318) 518-1389

On 4/15/2017 4:56 PM, Matt Zilmer wrote:

Very true!

Got back in front of my desktop 'puter and made an Excel worksheet to
calculate the characteristic impedance at various spacings and wire
sizes.  The real variable is the ratio of spacing divided by wire
diameter (only the ratio matters). Everything else in the formula is a
constant for our purposes.

16 AWG, 1 inchspacing:  Zc = 436 ohms

16 AWG, 2 inchspacing: Zc= 519 ohms

16 AWG, 3 inch spacing: Zc= 567 ohms

18 AWG, 1 inch sp:  Zc = 464 ohms

18 AWG, 2 inch sp:  Zc = 547 ohms

18 AWG, 3 inch sp:  Zc = 595 ohms

Or for you QRO ops: 3/0 AWG, 9 inch spacing: Zc = 450 ohms.  3/0
(three-aught) is quite hefty, being 0.4" in diameter. Probably
overkill for the average Joe Ham.

The commercial ladder line I use is 18 AWG with about 0.9" spacing
(hard to measure), giving 451 ohms. I think there is a lot of this
type in use.

Anyway, for the wire sizes and spacings we would normally use, the Zc
is nearly the same value, which is all I was saying before.

The formulas for all this are pretty well documented at
http://hamwaves.com/zc.circular/en/index.html.

73,

matt W6NIA

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-- unknonwn

Matt Zilmer, W6NIA
[Shiraz]

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Re: [Elecraft] OT; Feedline question

[Richard Fjeld]

Okay, and thanks to all for the info which I will save.

What made me curious is that twin lead is stated in steps of 150 ohms. 
IE. 300, 450, 600.
I assumed it was to match the impedance of certain antennas such as a 
folded dipole, etc.
Since I understand my loop to be a non-resonant antenna, and using a 
manual tuner, I thought
I'd be okay to change the spacer dims, but I wondered if I was 
over-looking something.

Thanks again,

Dick, n0ce



On 4/15/2017 11:39 AM, Richard Fjeld wrote:
> Forgive me for the OT, but there are many antenna people here above my
> pay-grade.
>
> I need to replace the spacers on my ladder line.  If I deviate from the
> standard spacer length for impedance
> (separation between conductors), are there problems I'm not thinking
> of?  I use a quality manual tuner, and
> an 80 meter delta loop.
>
> Perhaps it would be best to reply off line for this.  Thank you in advance.
>
> Dick, n0ce
>

-- 

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Re: [Elecraft] OT; Feedline question

[Clay Autery]

Thanks

So, these numbers are for BARE copper, right?
Using insulated wire changes things a bunch

For instance 18 GA THHN/THWN has an approx. dc of 2.35, XLPE has a dc of
5 or so  As the dielectric constant gets larger, things get real
fast.

18 GA THHN/THWN...  (dc = 2.35 approx.)

To get the same 464 Ohms, the Center to center distance must increase to
7.52 inches or so...
The impedance with the quoted 1, 2, and 3 inch "D":

1" = 305-306 Ohms

2" = 359-360 Ohms

3" = 391-392 Ohms

I use 300 Ohm, 18 GA copper twin-lead with foam over wires and some hard
plastic over that  It's close to true 300 Ohm...

I'll have to go calculate the min size safe against various power
levels...  The separation distances get big fast with increase in the
conductor diameter, too.

73,

PS - there is an argument to be made for NOT using bare wire  if
anything MIGHT touch the feedline...   and wet wire   wet wire
changes performance a lot...  built with insulated wire, the changes are
MUCH smaller with wet wire...

__
Clay Autery, KY5G
MONTAC Enterprises
(318) 518-1389

On 4/15/2017 4:56 PM, Matt Zilmer wrote:
> Very true!
>
> Got back in front of my desktop 'puter and made an Excel worksheet to
> calculate the characteristic impedance at various spacings and wire
> sizes.  The real variable is the ratio of spacing divided by wire
> diameter (only the ratio matters). Everything else in the formula is a
> constant for our purposes.
>
> 16 AWG, 1 inchspacing:  Zc = 436 ohms
>
> 16 AWG, 2 inchspacing: Zc= 519 ohms
>
> 16 AWG, 3 inch spacing: Zc= 567 ohms
>
> 18 AWG, 1 inch sp:  Zc = 464 ohms
>
> 18 AWG, 2 inch sp:  Zc = 547 ohms
>
> 18 AWG, 3 inch sp:  Zc = 595 ohms
>
> Or for you QRO ops: 3/0 AWG, 9 inch spacing: Zc = 450 ohms.  3/0
> (three-aught) is quite hefty, being 0.4" in diameter. Probably
> overkill for the average Joe Ham.
>
> The commercial ladder line I use is 18 AWG with about 0.9" spacing
> (hard to measure), giving 451 ohms. I think there is a lot of this
> type in use.
>
> Anyway, for the wire sizes and spacings we would normally use, the Zc
> is nearly the same value, which is all I was saying before.
>
> The formulas for all this are pretty well documented at
> http://hamwaves.com/zc.circular/en/index.html.
>
> 73,
>
> matt W6NIA
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Re: [Elecraft] OT; Feedline question

[Matt Zilmer]

Very true!

Got back in front of my desktop 'puter and made an Excel worksheet to 
calculate the characteristic impedance at various spacings and wire 
sizes.  The real variable is the ratio of spacing divided by wire 
diameter (only the ratio matters). Everything else in the formula is a 
constant for our purposes.


16 AWG, 1 inchspacing:  Zc = 436 ohms

16 AWG, 2 inchspacing: Zc= 519 ohms

16 AWG, 3 inch spacing: Zc= 567 ohms

18 AWG, 1 inch sp:  Zc = 464 ohms

18 AWG, 2 inch sp:  Zc = 547 ohms

18 AWG, 3 inch sp:  Zc = 595 ohms

Or for you QRO ops: 3/0 AWG, 9 inch spacing: Zc = 450 ohms.  3/0 
(three-aught) is quite hefty, being 0.4" in diameter. Probably overkill 
for the average Joe Ham.


The commercial ladder line I use is 18 AWG with about 0.9" spacing (hard 
to measure), giving 451 ohms. I think there is a lot of this type in use.


Anyway, for the wire sizes and spacings we would normally use, the Zc is 
nearly the same value, which is all I was saying before.


The formulas for all this are pretty well documented at 
http://hamwaves.com/zc.circular/en/index.html.


73,

matt W6NIA


On 4/15/2017 10:52 AM, Lynn W. Taylor, WB6UUT wrote:

Off-list one person learns.  On-list we all learn.

On 4/15/2017 10:16 AM, Matt Zilmer wrote:

This is an amateur topic, so there's no reason to take it offline, imho.

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"A delay is better than a disaster."
-- unknonwn

Matt Zilmer, W6NIA
[Shiraz]

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Re: [Elecraft] OT; Feedline question

[Lynn W. Taylor, WB6UUT]

Off-list one person learns.  On-list we all learn.

On 4/15/2017 10:16 AM, Matt Zilmer wrote:

This is an amateur topic, so there's no reason to take it offline, imho.

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Re: [Elecraft] OT; Feedline question

[Matt Zilmer]

This is an amateur topic, so there's no reason to take it offline, imho.

If you run the impedance vs spacing calculations, you'll see the spacing
doesn't make a whale of a lot of difference.  I don't have the numbers
here, but I switched from 1/2 of a BIC pen  body (hole centers about 2"
apart) to some ceramic spacers another ham gave me a box full of.  The
new spacers had centers about 3.2" apart.  I had to re-tune the ATU on
most bands, but everything continued to work fine.  From (a tired old)
memory, the impedance varied from about 450 ohms to something like 600
ohms, but let someone on a computer run the calcs for this.  It just
didn't make enough difference to worry about, but did change the ladder
feed's impedance.

This antenna is a doublet about 180' long at 45 feet height, fed with
the ladder line (61' of it, from memory).  The ladder line terminates
into a 1:1 balun (Elecraft BL2) and the last 20 feet is LMR400 low-loss
coax back to the station's antenna switch.  It continues to work just as
well as with the earlier ladder spacers.

73,

matt W6NIA


On 04/15/2017 09:39 AM, Richard Fjeld wrote:
> Forgive me for the OT, but there are many antenna people here above my 
> pay-grade.
>
> I need to replace the spacers on my ladder line.  If I deviate from the 
> standard spacer length for impedance
> (separation between conductors), are there problems I'm not thinking 
> of?  I use a quality manual tuner, and
> an 80 meter delta loop.
>
> Perhaps it would be best to reply off line for this.  Thank you in advance.
>
> Dick, n0ce
>

-- 
"Always store beer in a dark place." -- R. Heinlein

Matt Zilmer, W6NIA
[Voignier]

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[Elecraft] OT; Feedline question

[Richard Fjeld]

Forgive me for the OT, but there are many antenna people here above my 
pay-grade.

I need to replace the spacers on my ladder line.  If I deviate from the 
standard spacer length for impedance
(separation between conductors), are there problems I'm not thinking 
of?  I use a quality manual tuner, and
an 80 meter delta loop.

Perhaps it would be best to reply off line for this.  Thank you in advance.

Dick, n0ce

-- 

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