Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

[CUTTER DAVID via Elecraft]

Skip

Was any attempt made to redress the imbalance?

David G3UNA

> On 17 July 2020 at 03:19 Fred Jensen  mailto:k6...@foothill.net > wrote:
> 
> 
> They were around somewhat before the patent in several forms, and they
> were around in 1960, which is the last time I looked hence my estimate
> of 60 years.  Lots of other "balanced" antennas fed with open line were
> also in use commercially during that rough period, they too exhibited
> the same characteristic ... while carefully engineered to be balanced,
> RF currents in the two wires never were exactly balanced, which was the
> original and only point.
> 
> I still have an RF ammeter in my junk box, from some airborne WW2 radio
> I think.  It's probably an antique by now.
> 
> 73,
> Fred ["Skip"] K6DGW
> Sparks NV DM09dn
> Washoe County
> 
> On 7/16/2020 5:47 PM, donov...@starpower.net 
> mailto:donov...@starpower.net wrote:
> 
> > > Hi Skip,
> > 
> > Conceptionally you're correct about rhombics and V-beams but your 
> > time
> > frame is way off.
> > 
> > Edmond Bruce's rhombic antenna patent was filed in 1931.
> > 
> > www.aktuellum.com/mobile/circuits/antenna-patent
> > 
> > 
> > ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1685103
> > 
> > 
> > The heyday for the rhombic ran from the 1930s through the 1970s with
> > the advent of satellite communications.  The 200 foot tower for my
> > 40 meter stacked 3 element Yagis came from a decommissioned
> > Laport Rhombic installed at the NSS receive site in Cheltenham MD.
> > We removed it in 1985, but it hadn't been used for years.
> > 
> > 73
> > Frank
> > W3
> > 
> > > __
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft@mailman.qth.net mailto:Elecraft@mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to d.cut...@ntlworld.com mailto:d.cut...@ntlworld.com
> 
__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

[Victor Rosenthal 4X6GP]

I took great care in the construction of my rotary dipole and feed 
system to make it as balanced as possible. I made a clamp-on device from 
a split ferrite bead that I can use to measure the relative currents in 
the open line conductors, and they are very close.


There is one direction in which there is measurable unbalance due to a 
nearby object, but unfortunately this is also the direction of my major 
source of noise, another building 100m away, so it's not possible to 
tell whether the unbalance contributes to the noise or not.


Someone else said that balanced lines don't reject common mode noise. 
It's true that common mode noise currents can flow on the feedline, but 
they are rejected by the balanced link-coupled tuner at the transmitter end.


I unfortunately don't have a choked coax-fed dipole to compare it to, 
but it is much quieter than the previous antenna, a coax-fed multiband 
vertical. And it is also a far better transmitting antenna.


Let's hear it for 1930s technology!

73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
.
On 17/07/2020 0:41, Fred Jensen wrote:

Indeed!  Probably the least unbalanced of "balanced" antenna systems
 that ever existed were the HF point-to-point rhombics and V-beams at
the RCA, Mackay, and Marconi shore stations in the first 60 or so
years of the 20th century.  Despite very precise engineering to make
them balanced, the RF currents in each side of the open feeders were
never exactly the same.

As a teenage ham, I tended to think in absolutes and exactitudes. If
my Heath MM-1 multimeter said the screen voltage was 176.5 V, I
believed it was, exactly, and if the spec said 177.5 V, I needed to
do something to "fix" it.  If the ARRL Handbook said the two halves
of my 40 meter dipole needed to be exactly 32.9114 feet, I believed
that the antenna would not work if I didn't assure my dipole was
exactly 32.9114 on each side.  As I grew older, both in age and ham
longevity, I realized my Elmer was right when reminded me on multiple
occasions, "We're amateurs.  Most often, 'close' is good enough."

Seems like many today are convinced that 32.9114 ft will work but 
32.9000 ft won't.


73, Fred ["Skip"] K6DGW Sparks NV DM09dn Washoe County

On 7/16/2020 1:00 PM, Jim Brown wrote:

On 7/16/2020 1:14 AM, Victor Rosenthal 4X6GP wrote:

If the antenna is well-balanced and fed via a true balanced
antenna tuner (preferably link-coupled) then there shouldn't be a
problem with common mode currents.


Few ham antennas are perfectly balanced -- they are often
unbalanced by their surroundings. For example, ground slope,
unequal heights of the two halves, other conductors around the
antenna, even vegetation. And yes, all elements of the antenna
system, including the feedline, the antenna, and matching at both
ends, contribute to the balance of the SYSTEM.

THAT'S why it's wrong to talk about "balanced line," using
"parallel wire" or 2-wire" line instead.

73, Jim K9YC


__ 
Elecraft mailing list 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
email list: http://www.qsl.net/donate.html Message delivered to
k2vco@gmail.com

__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

[Fred Jensen]

They were around somewhat before the patent in several forms, and they 
were around in 1960, which is the last time I looked hence my estimate 
of 60 years.  Lots of other "balanced" antennas fed with open line were 
also in use commercially during that rough period, they too exhibited 
the same characteristic ... while carefully engineered to be balanced, 
RF currents in the two wires never were exactly balanced, which was the 
original and only point.


I still have an RF ammeter in my junk box, from some airborne WW2 radio 
I think.  It's probably an antique by now.


73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 7/16/2020 5:47 PM, donov...@starpower.net wrote:

Hi Skip,

Conceptionally you're correct about rhombics and V-beams but your time 
frame is way off.


Edmond Bruce's rhombic antenna patent was filed in 1931.

www.aktuellum.com/mobile/circuits/antenna-patent 



ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1685103 



The heyday for the rhombic ran from the 1930s through the 1970s with
the advent of satellite communications.  The 200 foot tower for my
40 meter stacked 3 element Yagis came from a decommissioned
Laport Rhombic installed at the NSS receive site in Cheltenham MD.
We removed it in 1985, but it hadn't been used for years.

73
Frank
W3



__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

[donovanf]

Hi Skip, 


Conceptionally you're correct about rhombics and V-beams but your time frame is 
way off. 


Edmond Bruce's rhombic antenna patent was filed in 1931. 


www.aktuellum.com/mobile/circuits/antenna-patent 


ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1685103 


The heyday for the rhombic ran from the 1930s through the 1970s with 
the advent of satellite communications. The 200 foot tower for my 
40 meter stacked 3 element Yagis came from a decommissioned 
Laport Rhombic installed at the NSS receive site in Cheltenham MD. 
We removed it in 1985, but it hadn't been used for years. 


73 
Frank 
W3 






- Original Message -

From: "Fred Jensen"  
To: elecraft@mailman.qth.net 
Sent: Thursday, July 16, 2020 9:41:21 PM 
Subject: Re: [Elecraft] KPA1500 in the IARU Contest Last weekend 

Indeed! Probably the least unbalanced of "balanced" antenna systems 
that ever existed were the HF point-to-point rhombics and V-beams at the 
RCA, Mackay, and Marconi shore stations in the first 60 or so years of 
the 20th century. Despite very precise engineering to make them 
balanced, the RF currents in each side of the open feeders were never 
exactly the same. 

As a teenage ham, I tended to think in absolutes and exactitudes. If my 
Heath MM-1 multimeter said the screen voltage was 176.5 V, I believed it 
was, exactly, and if the spec said 177.5 V, I needed to do something to 
"fix" it. If the ARRL Handbook said the two halves of my 40 meter 
dipole needed to be exactly 32.9114 feet, I believed that the antenna 
would not work if I didn't assure my dipole was exactly 32.9114 on each 
side. As I grew older, both in age and ham longevity, I realized my 
Elmer was right when reminded me on multiple occasions, "We're 
amateurs. Most often, 'close' is good enough." 

Seems like many today are convinced that 32.9114 ft will work but 
32.9000 ft won't. 

73, 
Fred ["Skip"] K6DGW 
Sparks NV DM09dn 
Washoe County 

On 7/16/2020 1:00 PM, Jim Brown wrote: 
> On 7/16/2020 1:14 AM, Victor Rosenthal 4X6GP wrote: 
>> If the antenna is well-balanced and fed via a true balanced antenna 
>> tuner (preferably link-coupled) then there shouldn't be a problem 
>> with common mode currents. 
> 
> Few ham antennas are perfectly balanced -- they are often unbalanced 
> by their surroundings. For example, ground slope, unequal heights of 
> the two halves, other conductors around the antenna, even vegetation. 
> And yes, all elements of the antenna system, including the feedline, 
> the antenna, and matching at both ends, contribute to the balance of 
> the SYSTEM. 
> 
> THAT'S why it's wrong to talk about "balanced line," using "parallel 
> wire" or 2-wire" line instead. 
> 
> 73, Jim K9YC 

__ 
Elecraft mailing list 
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 email list: http://www.qsl.net/donate.html 
Message delivered to donov...@starpower.net 
__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

[Charlie T]

Yeah, I remember as a new ham of 14, I asked my dad to buy a 50 foot piece of 
RG-58/u at Electronics Wholesalers in Washington DC.
He came home with 50 feet of RG58C/u which has a stranded center conductor and 
a characteristic Z of 53Ω.

I politely asked him to return it since it wasn't the correct impedance.
The counter clerk tried to explain that it was "better" because of  the more 
flexible center and the very slight difference in characteristic impedance 
wouldn't make ANY difference in performance, but he insisted and came away with 
a new piece of RG-58/u.  I think l I used it to string up a 15M dipole between 
our two chimneys.

Never DID get that %$#@ Globe Chief to work on 15 though.
For some reason, it had more output on 14 MHz than 21 even when I had the 
bandswitch on 15M 
My entire Novice career was spent on 40M CW and 2M AM back when Novices had 145 
to 147 MHz.

73,   k3ICH  (ex KN3ICH in1959) 


-Original Message-
From: elecraft-boun...@mailman.qth.net  On 
Behalf Of Fred Jensen
Sent: Thursday, July 16, 2020 5:41 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

Indeed!  Probably the least unbalanced of "balanced" antenna systems that ever 
existed were the HF point-to-point rhombics and V-beams at the RCA, Mackay, and 
Marconi shore stations in the first 60 or so years of the 20th century.  
Despite very precise engineering to make them balanced, the RF currents in each 
side of the open feeders were never exactly the same.

As a teenage ham, I tended to think in absolutes and exactitudes. If my Heath 
MM-1 multimeter said the screen voltage was 176.5 V, I believed it was, 
exactly, and if the spec said 177.5 V, I needed to do something to "fix" it.  
If the ARRL Handbook said the two halves of my 40 meter dipole needed to be 
exactly 32.9114 feet, I believed that the antenna would not work if I didn't 
assure my dipole was exactly 32.9114 on each side.  As I grew older, both in 
age and ham longevity, I realized my Elmer was right when reminded me on 
multiple occasions, "We're amateurs.  Most often, 'close' is good enough."

Seems like many today are convinced that 32.9114 ft will work but
32.9000 ft won't.

73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County
 

__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

[Fred Jensen]

Indeed!  Probably the least unbalanced of "balanced" antenna systems 
that ever existed were the HF point-to-point rhombics and V-beams at the 
RCA, Mackay, and Marconi shore stations in the first 60 or so years of 
the 20th century.  Despite very precise engineering to make them 
balanced, the RF currents in each side of the open feeders were never 
exactly the same.


As a teenage ham, I tended to think in absolutes and exactitudes. If my 
Heath MM-1 multimeter said the screen voltage was 176.5 V, I believed it 
was, exactly, and if the spec said 177.5 V, I needed to do something to 
"fix" it.  If the ARRL Handbook said the two halves of my 40 meter 
dipole needed to be exactly 32.9114 feet, I believed that the antenna 
would not work if I didn't assure my dipole was exactly 32.9114 on each 
side.  As I grew older, both in age and ham longevity, I realized my 
Elmer was right when reminded me on multiple occasions, "We're 
amateurs.  Most often, 'close' is good enough."


Seems like many today are convinced that 32.9114 ft will work but 
32.9000 ft won't.


73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 7/16/2020 1:00 PM, Jim Brown wrote:

On 7/16/2020 1:14 AM, Victor Rosenthal 4X6GP wrote:
If the antenna is well-balanced and fed via a true balanced antenna 
tuner (preferably link-coupled) then there shouldn't be a problem 
with common mode currents.


Few ham antennas are perfectly balanced -- they are often unbalanced 
by their surroundings. For example, ground slope, unequal heights of 
the two halves, other conductors around the antenna, even vegetation. 
And yes, all elements of the antenna system, including the feedline, 
the antenna, and matching at both ends, contribute to the balance of 
the SYSTEM.


THAT'S why it's wrong to talk about "balanced line," using "parallel 
wire" or 2-wire" line instead.


73, Jim K9YC


__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

[Jim Brown]

On 7/16/2020 1:14 AM, Victor Rosenthal 4X6GP wrote:
If the antenna is well-balanced and fed via a true balanced antenna 
tuner (preferably link-coupled) then there shouldn't be a problem with 
common mode currents.


Few ham antennas are perfectly balanced -- they are often unbalanced by 
their surroundings. For example, ground slope, unequal heights of the 
two halves, other conductors around the antenna, even vegetation. And 
yes, all elements of the antenna system, including the feedline, the 
antenna, and matching at both ends, contribute to the balance of the SYSTEM.


THAT'S why it's wrong to talk about "balanced line," using "parallel 
wire" or 2-wire" line instead.


73, Jim K9YC
__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

[Walter Underwood]

There is some sort of popular folk theorem that open wire feed line doesn’t 
carry common mode currents. It is obviously wrong. Both wires high, both wires 
low, and that is common mode. Any RF that excites both dipole elements high 
against ground will cause common mode currents on the feed line. “Balance” does 
not fix that.

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

> On Jul 16, 2020, at 1:14 AM, Victor Rosenthal 4X6GP  
> wrote:
> 
> Re open-wire fed antennas:
> 
> If the antenna is well-balanced and fed via a true balanced antenna tuner 
> (preferably link-coupled) then there shouldn't be a problem with common mode 
> currents.
> 
> Yes, you have to worry about nearby objects unbalancing the antenna, which is 
> less of a problem with a choked coax-fed dipole. But being able to use a very 
> simple single antenna from (for example) 7 to 28 mHz. with relatively good 
> efficiency is advantageous.
> 
> My experiments with baluns seem to indicate that just using a current balun 
> to go from an unbalanced transmitter or tuner to a balanced line works poorly 
> unless you cancel out the reactance with a balanced network on the antenna 
> side of the balun. All these tuners with "balanced" outputs provided by a 
> balun (often a voltage balun) do not work well at all.
> 
> My best result with balanced lines has been with the Johnson Matchbox. It's a 
> shame that there doesn't seem to be an equivalent available today (and it 
> wouldn't be easy to procure the parts to build one).
> 
> 73,
> Victor, 4X6GP
> Rehovot, Israel
> Formerly K2VCO
> CWops no. 5
> http://www.qsl.net/k2vco/
> On 16/07/2020 6:26, Jim Brown wrote:
>> On 7/15/2020 1:36 PM, CUTTER DAVID wrote:
>>> It's all about size.  Bigger core helps, 
>> Dave,
>> No, it is NOT about size. It is about design of the entire antenna system, 
>> including the antenna, the feedline, and other parts needed to make the 
>> SYSTEM work. The principal characteristic of a common mode choke is the 
>> resistive component of its common mode impedance at the operating 
>> frequency(ies) where it will be used. Further, dissipation in the choke 
>> occurs at least as much in the WIRE that is wound around the core as in the 
>> core itself.
>> There is another fundamental error in many antenna systems that ONLY looks 
>> at matching to the transmitter at the transmitter, ignoring the match 
>> between the antenna and the transmission line, using high impedance, 
>> parallel wire line, and using a random center-fed or off-center fed 
>> horizontal wire on all bands. Yes, the transmitter can be made to supply 
>> power to the feedline, yes, it will get to the antenna, and yes, it will 
>> radiate. But it may not receive all that well due to common mode current on 
>> the line from noise sources in our own homes and those of our neighbors. 
>> THAT is the problem with using a decades-old design for a world where there 
>> was 20 dB less noise than most of us face today.
>> so a core that is OK for ssb
>>> and cw might be undersized for AM or some data modes. Just like linear 
>>> amplifiers.
>> So it is NOT the size of the core, it's the design of the antenna system. 
>> HFTA author and retired ARRL Antenna Book and Handbook editor Dean Straw, 
>> N6BV, published an excellent piece in QST 6-8 years ago called "Don't Blow 
>> Up Your Balun," in which he pointed out the differential mode dissipation in 
>> chokes, which can be extremely high if the choke is at a very high current 
>> point in a mismatched line. When he passed it to me for review, I noted that 
>> these losses were in addition to the common mode dissipation, and he revised 
>> the piece to reflect that.
>>  you can't
>>> label something poorly designed because it doesn't pass the BOK test.
>> BOK?
>> 73, Jim K9YC
> __
> Elecraft mailing list
> 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 email list: http://www.qsl.net/donate.html
> Message delivered to wun...@wunderwood.org

__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

[CUTTER DAVID via Elecraft]

Jim
We're drifting off topic and you're pushing at an open door. 

I accept that wire size has an influence, but in my experience on smaller cores 
(UK limit is 400W) wound with RG316 I have observed the core getting hotter 
than the wire.  

BOK = Brick On Key.  I think it was Alpha that used this in their advertising.

So, in the protagonist's system, if he finds his swr climbing for no apparent 
reason, rather than blaming the linear it might simply be the core of the choke 
getting too hot with continuous use.  A bigger core (or doubling up) helped me 
and it might help him. 

David G3UNA


> On 16 July 2020 at 04:26 Jim Brown  wrote:
> 
> 
> On 7/15/2020 1:36 PM, CUTTER DAVID wrote:
> > It's all about size.  Bigger core helps, 
> 
> Dave,
> 
> No, it is NOT about size. It is about design of the entire antenna 
> system, including the antenna, the feedline, and other parts needed to 
> make the SYSTEM work. The principal characteristic of a common mode 
> choke is the resistive component of its common mode impedance at the 
> operating frequency(ies) where it will be used. Further, dissipation in 
> the choke occurs at least as much in the WIRE that is wound around the 
> core as in the core itself.
> 
> There is another fundamental error in many antenna systems that ONLY 
> looks at matching to the transmitter at the transmitter, ignoring the 
> match between the antenna and the transmission line, using high 
> impedance, parallel wire line, and using a random center-fed or 
> off-center fed horizontal wire on all bands. Yes, the transmitter can be 
> made to supply power to the feedline, yes, it will get to the antenna, 
> and yes, it will radiate. But it may not receive all that well due to 
> common mode current on the line from noise sources in our own homes and 
> those of our neighbors. THAT is the problem with using a decades-old 
> design for a world where there was 20 dB less noise than most of us face 
> today.
> 
> so a core that is OK for ssb
> > and cw might be undersized for AM or some data modes. Just like linear 
> > amplifiers.
> 
> So it is NOT the size of the core, it's the design of the antenna 
> system. HFTA author and retired ARRL Antenna Book and Handbook editor 
> Dean Straw, N6BV, published an excellent piece in QST 6-8 years ago 
> called "Don't Blow Up Your Balun," in which he pointed out the 
> differential mode dissipation in chokes, which can be extremely high if 
> the choke is at a very high current point in a mismatched line. When he 
> passed it to me for review, I noted that these losses were in addition 
> to the common mode dissipation, and he revised the piece to reflect that.
> 
>   you can't
> > label something poorly designed because it doesn't pass the BOK test.
> 
> BOK?
> 
> 73, Jim K9YC
> 
> __
> Elecraft mailing list
> 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 email list: http://www.qsl.net/donate.html
> Message delivered to d.cut...@ntlworld.com
__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

[Victor Rosenthal 4X6GP]

Re open-wire fed antennas:

If the antenna is well-balanced and fed via a true balanced antenna 
tuner (preferably link-coupled) then there shouldn't be a problem with 
common mode currents.


Yes, you have to worry about nearby objects unbalancing the antenna, 
which is less of a problem with a choked coax-fed dipole. But being able 
to use a very simple single antenna from (for example) 7 to 28 mHz. with 
relatively good efficiency is advantageous.


My experiments with baluns seem to indicate that just using a current 
balun to go from an unbalanced transmitter or tuner to a balanced line 
works poorly unless you cancel out the reactance with a balanced network 
on the antenna side of the balun. All these tuners with "balanced" 
outputs provided by a balun (often a voltage balun) do not work well at all.


My best result with balanced lines has been with the Johnson Matchbox. 
It's a shame that there doesn't seem to be an equivalent available today 
(and it wouldn't be easy to procure the parts to build one).


73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
On 16/07/2020 6:26, Jim Brown wrote:

On 7/15/2020 1:36 PM, CUTTER DAVID wrote:
It's all about size.  Bigger core helps, 


Dave,

No, it is NOT about size. It is about design of the entire antenna 
system, including the antenna, the feedline, and other parts needed to 
make the SYSTEM work. The principal characteristic of a common mode 
choke is the resistive component of its common mode impedance at the 
operating frequency(ies) where it will be used. Further, dissipation in 
the choke occurs at least as much in the WIRE that is wound around the 
core as in the core itself.


There is another fundamental error in many antenna systems that ONLY 
looks at matching to the transmitter at the transmitter, ignoring the 
match between the antenna and the transmission line, using high 
impedance, parallel wire line, and using a random center-fed or 
off-center fed horizontal wire on all bands. Yes, the transmitter can be 
made to supply power to the feedline, yes, it will get to the antenna, 
and yes, it will radiate. But it may not receive all that well due to 
common mode current on the line from noise sources in our own homes and 
those of our neighbors. THAT is the problem with using a decades-old 
design for a world where there was 20 dB less noise than most of us face 
today.


so a core that is OK for ssb
and cw might be undersized for AM or some data modes. Just like linear 
amplifiers.


So it is NOT the size of the core, it's the design of the antenna 
system. HFTA author and retired ARRL Antenna Book and Handbook editor 
Dean Straw, N6BV, published an excellent piece in QST 6-8 years ago 
called "Don't Blow Up Your Balun," in which he pointed out the 
differential mode dissipation in chokes, which can be extremely high if 
the choke is at a very high current point in a mismatched line. When he 
passed it to me for review, I noted that these losses were in addition 
to the common mode dissipation, and he revised the piece to reflect that.


  you can't

label something poorly designed because it doesn't pass the BOK test.


BOK?

73, Jim K9YC

__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

[Jim Brown]

On 7/15/2020 1:36 PM, CUTTER DAVID wrote:
It's all about size.  Bigger core helps, 


Dave,

No, it is NOT about size. It is about design of the entire antenna 
system, including the antenna, the feedline, and other parts needed to 
make the SYSTEM work. The principal characteristic of a common mode 
choke is the resistive component of its common mode impedance at the 
operating frequency(ies) where it will be used. Further, dissipation in 
the choke occurs at least as much in the WIRE that is wound around the 
core as in the core itself.


There is another fundamental error in many antenna systems that ONLY 
looks at matching to the transmitter at the transmitter, ignoring the 
match between the antenna and the transmission line, using high 
impedance, parallel wire line, and using a random center-fed or 
off-center fed horizontal wire on all bands. Yes, the transmitter can be 
made to supply power to the feedline, yes, it will get to the antenna, 
and yes, it will radiate. But it may not receive all that well due to 
common mode current on the line from noise sources in our own homes and 
those of our neighbors. THAT is the problem with using a decades-old 
design for a world where there was 20 dB less noise than most of us face 
today.


so a core that is OK for ssb
and cw might be undersized for AM or some data modes. Just like linear 
amplifiers.


So it is NOT the size of the core, it's the design of the antenna 
system. HFTA author and retired ARRL Antenna Book and Handbook editor 
Dean Straw, N6BV, published an excellent piece in QST 6-8 years ago 
called "Don't Blow Up Your Balun," in which he pointed out the 
differential mode dissipation in chokes, which can be extremely high if 
the choke is at a very high current point in a mismatched line. When he 
passed it to me for review, I noted that these losses were in addition 
to the common mode dissipation, and he revised the piece to reflect that.


 you can't

label something poorly designed because it doesn't pass the BOK test.


BOK?

73, Jim K9YC

__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

[CUTTER DAVID via Elecraft]

Size is the most important parameter. 
 
I've read your tutorials several times and they are an inspiration but it's 
just like linear amplifiers: you can't say an amplifier designed for 
intermittent service like ssb or cw is poorly designed because it doesn't pass 
the BOK test. It's horses for courses. A properly designed choke for an ocfd 
will not over-heat but these are few and far between it seems.

David G3UNA/G6CP

> On 15 July 2020 at 21:07 Jim Brown  wrote:
> 
> 
> On 7/15/2020 11:46 AM, CUTTER DAVID via Elecraft wrote:
> > Ferrite-cored chokes (balun) heat up and change apparent swr.
> 
> Not if they are properly designed and properly applied. And not all 
> antennas can be choked -- in general, only resonant antennas can be 
> effectively choked. Chokes applied to non-resonant and/or poorly 
> balanced antennas (like OCF wires) are, in general, NOT effective, and 
> WILL likely overheat.
> 
> I suggest a study of
> k9yc.com/RFI-Ham.pdf and
> http://k9yc.com/2018Cookbook.pdf
> 
> 73, Jim K9YC
> __
> Elecraft mailing list
> 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 email list: http://www.qsl.net/donate.html
> Message delivered to d.cut...@ntlworld.com
__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

[CUTTER DAVID via Elecraft]

__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

[Jim Brown]

On 7/15/2020 11:46 AM, CUTTER DAVID via Elecraft wrote:

Ferrite-cored chokes (balun) heat up and change apparent swr.


Not if they are properly designed and properly applied. And not all 
antennas can be choked -- in general, only resonant antennas can be 
effectively choked. Chokes applied to non-resonant and/or poorly 
balanced antennas (like OCF wires) are, in general, NOT effective, and 
WILL likely overheat.


I suggest a study of
k9yc.com/RFI-Ham.pdf and
http://k9yc.com/2018Cookbook.pdf

73, Jim K9YC
__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

[CUTTER DAVID via Elecraft]

Ferrite-cored chokes (balun) heat up and change apparent swr.  

David G3UNA/G6CP

> On 15 July 2020 at 17:36 j...@kk9a.com wrote:
> 
> 
> That is quite an assumption.  A 2el 40m beam with large efficient  
> High-Q loading coils will have less bandwidth than for example one of  
> the popular US manufactured beams that use 68 turns of small wire in  
> each coil.  The latter is more likely to have heating issues.  I have  
> never noticed any SWR changes or amplifier re-tuning with my 40m  
> OptiBeams during heavy use.
> 
> John KK9A
> 
> 
> Jim Miller AB3CV wrote:
> 
> Since it is so narrow I suspect it may be a trapped design or have loading
> coils which at 1500w may be heating and detuning as a result.
> 
> 73
> 
> jim ab3cv
> 
> On Wed, Jul 15, 2020 at 11:45 AM Ray Spreadbury via Elecraft <
> elecraft at mailman.qth.net> wrote:
> 
> >
> >
> > A correspondent asked me why I needed to tune a resonant antenna.
> > The reason was because although the Yagi was tuned to resonate at about
> > 7.130MHz it unfortunately has a rather narrow bandwidth. I needed to
> > operate SSB in this contest in ITU Region 1 SSB, which is between 7.080MHz
> > and 7.200MHZ. At 7.080MHz the SWR (with tuner bypassed) was 1.75:1 & at
> > 7.200 was 1.95:1. I would be operating at power so I preferred to tune for
> > 1.1:1.
> > Yes I know the Yagi is not very good with that narrow bandwidth, but it is
> > what it is. Normally I operate CW only on 40M & tune it to 7.030 with the
> > bandwidth covering the preferred Region 1 CW portion of the band ie7.000 to
> > 7.040 and the tuner is not needed.
> > 73 Ray G3XLG
> 
> __
> Elecraft mailing list
> 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 email list: http://www.qsl.net/donate.html
> Message delivered to d.cut...@ntlworld.com
__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

[john]

That is quite an assumption.  A 2el 40m beam with large efficient  
High-Q loading coils will have less bandwidth than for example one of  
the popular US manufactured beams that use 68 turns of small wire in  
each coil.  The latter is more likely to have heating issues.  I have  
never noticed any SWR changes or amplifier re-tuning with my 40m  
OptiBeams during heavy use.


John KK9A


Jim Miller AB3CV wrote:

Since it is so narrow I suspect it may be a trapped design or have loading
coils which at 1500w may be heating and detuning as a result.

73

jim ab3cv

On Wed, Jul 15, 2020 at 11:45 AM Ray Spreadbury via Elecraft <
elecraft at mailman.qth.net> wrote:




A correspondent asked me why I needed to tune a resonant antenna.
The reason was because although the Yagi was tuned to resonate at about
7.130MHz it unfortunately has a rather narrow bandwidth. I needed to
operate SSB in this contest in ITU Region 1 SSB, which is between 7.080MHz
and 7.200MHZ. At 7.080MHz the SWR (with tuner bypassed) was 1.75:1 & at
7.200 was 1.95:1. I would be operating at power so I preferred to tune for
1.1:1.
Yes I know the Yagi is not very good with that narrow bandwidth, but it is
what it is. Normally I operate CW only on 40M & tune it to 7.030 with the
bandwidth covering the preferred Region 1 CW portion of the band ie7.000 to
7.040 and the tuner is not needed.
73 Ray G3XLG


__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last weekend

[Jim Miller]

Since it is so narrow I suspect it may be a trapped design or have loading
coils which at 1500w may be heating and detuning as a result.

73

jim ab3cv

On Wed, Jul 15, 2020 at 11:45 AM Ray Spreadbury via Elecraft <
elecraft@mailman.qth.net> wrote:

>
>
> A correspondent asked me why I needed to tune a resonant antenna.
> The reason was because although the Yagi was tuned to resonate at about
> 7.130MHz it unfortunately has a rather narrow bandwidth. I needed to
> operate SSB in this contest in ITU Region 1 SSB, which is between 7.080MHz
> and 7.200MHZ. At 7.080MHz the SWR (with tuner bypassed) was 1.75:1 & at
> 7.200 was 1.95:1. I would be operating at power so I preferred to tune for
> 1.1:1.
> Yes I know the Yagi is not very good with that narrow bandwidth, but it is
> what it is. Normally I operate CW only on 40M & tune it to 7.030 with the
> bandwidth covering the preferred Region 1 CW portion of the band ie7.000 to
> 7.040 and the tuner is not needed.
> 73 Ray G3XLG
>
>
> __
> Elecraft mailing list
> 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 email list: http://www.qsl.net/donate.html
> Message delivered to j...@jtmiller.com
>
__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last Weekend

[donovanf]

Or water... 


Are you sure your coaxial cable, balun and connectors are all dry? 


From your description, the last thing I'd examine is the KPA1500 


Good luck! 


73 
Frank 
W3LPL 



On Wed, Jul 15, 2020 at 11:19 AM Nr4c  wrote: 

> My first thought is “Heat”! 
> 
> 
> Sent from my iPhone 
> ...nr4c. bill 
> 
> 
> > On Jul 15, 2020, at 4:43 AM, Ray Spreadbury via Elecraft < 
> elecraft@mailman.qth.net> wrote: 
> > 
> > Hi 
> > 
> > I was a member of the UK HQ team for this 24hour IARU event last weekend 
> and 
> > was one of the two Ops on 40M SSB. 
> > 
> > We took it in turns to be the Run station every 4 hours and I was using a 
> > 40M 2-El yagi at 60ft. I noticed that every 30-60mins, I needed to do a 
> > re-tune on the KPA1500 to keep the SWR at or near to 1.1:1, as it seemed 
> to 
> > gradually creep up over time. The amp temp peaked at 70C but was mostly 
> at 
> > about 55C. The SWR never got above 1.5:1 using KPA1500 screen but I know 
> > that the yagi was really presenting about 1.6:1 at the run frequency. 
> When 
> > not operating as the Run station the other Op was in Partner mode 
> spotting 
> > mults & helping with call identification. 
> > 
> > We were using the WinTest logging program as this enables us to private 
> > network with the other UK HQ stations (one on CW & one on SSB for each 
> > contest band ie. a total 12 stations at any one time, plus Partners). 
> > Because of Covid, this year we were all single Ops working from home 
> rather 
> > than just a few multi op stations. 
> > 
> > My K3S & the KPA1500 worked faultlessly for the 24hours as did Wintest 
> but I 
> > wonder what was the cause of the SWR increasing over time & needing a 
> > re-tune? 
> > 
> > 73 Ray G3XLG 
> > 
> > __ 
> > Elecraft mailing list 
> > 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 email list: http://www.qsl.net/donate.html 
> > Message delivered to n...@widomaker.com 
> __ 
> Elecraft mailing list 
> 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 email list: http://www.qsl.net/donate.html 
> Message delivered to j...@jtmiller.com 
__ 
Elecraft mailing list 
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 email list: http://www.qsl.net/donate.html 
Message delivered to donov...@starpower.net 
__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last Weekend

[Jim Miller]

Describe your antenna system.

Jim ab3cv

On Wed, Jul 15, 2020 at 11:19 AM Nr4c  wrote:

> My first thought is “Heat”!
>
>
> Sent from my iPhone
> ...nr4c. bill
>
>
> > On Jul 15, 2020, at 4:43 AM, Ray Spreadbury via Elecraft <
> elecraft@mailman.qth.net> wrote:
> >
> > Hi
> >
> > I was a member of the UK HQ team for this 24hour IARU event last weekend
> and
> > was one of the two Ops on 40M SSB.
> >
> > We took it in turns to be the Run station every 4 hours and I was using a
> > 40M 2-El yagi at 60ft. I noticed that every 30-60mins, I needed to do a
> > re-tune on the KPA1500 to keep the SWR at or near to 1.1:1, as it seemed
> to
> > gradually creep up over time. The amp temp peaked at 70C but was mostly
> at
> > about 55C. The SWR never got above 1.5:1 using KPA1500 screen but I know
> > that the yagi was really presenting about 1.6:1 at the run frequency.
> When
> > not operating as the Run station the other Op was in Partner mode
> spotting
> > mults & helping with call identification.
> >
> > We were using the WinTest logging program as this enables us to private
> > network with the other UK HQ stations (one on CW & one on SSB for each
> > contest band ie. a total 12 stations at any one time, plus Partners).
> > Because of Covid, this year we were all single Ops working from home
> rather
> > than just a few multi op stations.
> >
> > My K3S & the KPA1500 worked faultlessly for the 24hours as did Wintest
> but I
> > wonder what was the cause of the SWR increasing over time & needing a
> > re-tune?
> >
> > 73 Ray G3XLG
> >
> > __
> > Elecraft mailing list
> > 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 email list: http://www.qsl.net/donate.html
> > Message delivered to n...@widomaker.com
> __
> Elecraft mailing list
> 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 email list: http://www.qsl.net/donate.html
> Message delivered to j...@jtmiller.com
__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA1500 in the IARU Contest Last Weekend

[Nr4c]

My first thought is “Heat”!


Sent from my iPhone
...nr4c. bill


> On Jul 15, 2020, at 4:43 AM, Ray Spreadbury via Elecraft 
>  wrote:
> 
> Hi
> 
> I was a member of the UK HQ team for this 24hour IARU event last weekend and
> was one of the two Ops on 40M SSB. 
> 
> We took it in turns to be the Run station every 4 hours and I was using a
> 40M 2-El yagi at 60ft. I noticed that every 30-60mins, I needed to do a
> re-tune on the KPA1500 to keep the SWR at or near to 1.1:1, as it seemed to
> gradually creep up over time. The amp temp peaked at 70C but was mostly at
> about 55C. The SWR never got above 1.5:1 using KPA1500 screen but I know
> that the yagi was really presenting about 1.6:1 at the run frequency. When
> not operating as the Run station the other Op was in Partner mode spotting
> mults & helping with call identification.
> 
> We were using the WinTest logging program as this enables us to private
> network with the other UK HQ stations (one on CW & one on SSB for each
> contest band ie. a total 12 stations at any one time, plus Partners).
> Because of Covid, this year we were all single Ops working from home rather
> than just a few multi op stations.
> 
> My K3S & the KPA1500 worked faultlessly for the 24hours as did Wintest but I
> wonder what was the cause of the SWR increasing over time & needing a
> re-tune?
> 
> 73 Ray G3XLG
> 
> __
> Elecraft mailing list
> 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 email list: http://www.qsl.net/donate.html
> Message delivered to n...@widomaker.com 
__
Elecraft mailing list
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 email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com