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A Good Antenna Length?

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Re: A Good Antenna Length?

Off center fed dipoles, Windoms and end fed half waves are primarily low power if not QRP antennas where you can do poorly with any antenna. They are prone to arcing, heating and RF where you don't want it. You are better off with conventional low radiation resistance antennas if you plan to use 100 watts or higher. The search for an antenna that will make QRP sound like a kilowatt is futile. The only way to do that is to have excellent conditions and infinite patience which will make anything sort of work.

Willis 'Cookie' Cooke, TDXS DX Chairman
K5EWJ & Trustee N5BPS, USS Cavalla, USS Stewart

On Saturday, July 5, 2014 11:55 AM, Dave <[hidden email]> wrote:

I tried a 40M OCFD for a while. I gave up on it and went back to a centre
fed dipole instead.

Even on 40M it didn't seem very good and I was plagued with RF getting into
PCs and them shutting down or periferals stopping working. Plus, despite
the hype, it didn't really seem to work well on other bands. The Antenna
analyser was very dismissive, showing resonances outside of the Amateur
bands and, on some that it was supposed to work on, no sign of any resonance
at all.

Dave (G0DJA)

----- Original Message -----
From: "Jim Brown" <[hidden email]>
To: <[hidden email]>
Sent: Saturday, July 05, 2014 2:24 PM
Subject: Re: [Elecraft] A Good Antenna Length?

> On 7/5/2014 2:05 AM, David Cutter wrote:
>> You might consider an off-centre-fed dipole with appropriate balun and
>> choke.
>
> Not if you're going to run power. An off center fed antenna generates high
> common mode voltage, which will fry even the best choke when running
> power. I wouldn't consider such an antenna at greater than 100W.
>
> 73, Jim K9YC
> ______________________________________________________________
> Elecraft mailing list
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Re: A Good Antenna Length?

Willis 'Cookie' Cooke, TDXS DX Chairman
K5EWJ & Trustee N5BPS, USS Cavalla, USS Stewart

On , WILLIS COOKE <[hidden email]> wrote:

Off center fed dipoles, Windoms and end fed half waves are primarily low power if not QRP antennas where you can do poorly with any antenna. They are prone to arcing, heating and RF where you don't want it. You are better off with conventional low radiation resistance antennas if you plan to use 100 watts or higher. The search for an antenna that will make QRP sound like a kilowatt is futile. The only way to do that is to have excellent conditions and infinite patience which will make anything sort of work.

Willis 'Cookie' Cooke, TDXS DX Chairman
K5EWJ & Trustee N5BPS, USS Cavalla, USS Stewart

On Saturday, July 5, 2014 11:55 AM, Dave <[hidden email]> wrote:

I tried a 40M OCFD for a while. I gave up on it and went back to a centre
fed dipole instead.

Even on 40M it didn't seem very good and I was plagued with RF getting into
PCs and them shutting down or
periferals stopping working. Plus, despite
the hype, it didn't really seem to work well on other bands. The Antenna
analyser was very dismissive, showing resonances outside of the Amateur
bands and, on some that it was supposed to work on, no sign of any resonance
at all.

Dave (G0DJA)

----- Original Message -----
From: "Jim Brown" <[hidden email]>
To: <[hidden email]>
Sent: Saturday, July 05, 2014 2:24 PM
Subject: Re: [Elecraft] A Good Antenna Length?

> On 7/5/2014 2:05 AM, David Cutter wrote:
>> You might consider an off-centre-fed dipole with appropriate balun and
>> choke.
>
> Not if you're going to run power. An off center fed antenna generates
high

> common mode voltage, which will fry even the best choke when running
> power. I wouldn't consider such an antenna at greater than 100W.
>
> 73, Jim K9YC
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
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> Message delivered to [hidden email]

JHRichards

Re: A Good Antenna Length?

In reply to this post by Dave-5

Lots of guys have good results with OCF dipoles all over the world.

I run a weekly nationwide net for a Brand X radio model using a 40-6
meter OCF dipole. I am the loud signal and I hear all and they all
hear me. Of course it helps I am in the Midwest, but still, I run 700
watts into it and NO CMC or other problems. I can run more power, but
don't because that is enough to get the job done. Power is not an
issue on my OCF dipole.

Best advice I ever received on OCF Dipoles comes from a guy who tested
several OCF dipoles for common mode noise, and then found the right type
of balun/choke to use. IT DOES make a difference how you build and
deploy it. If you run the feed line closer to one side than the other,
you get CMC. If you use the wrong balun, you get CMC.

See here: http://www.dj0ip.de/cmc-test/

Using a proper DUAL Core balun - where the transformer is wound on a
separate toroid from the choke wound on another toriod - it works fine
and you have no CMC noise issue.

Stop by my shack and have a listen. CMC "can" be a problem if you allow
it to be, but not if you pay attention to what you are doing. Again,
don't believe me... stop by the shack or join my net some Wed evening
and see. (We don't care what brand rig you own - its is ham radio and
it is all good)

Just MY take. This antenna works better than the AlphaDelta and home
brew fan dipoles I used to use... (although I cannot explain why the
others did not work as well, they should have...but who knows what they
were coupling with in my crowded little lot.)

Happy days.
--------------------- K8JHR ----------------------

On 7/5/2014 12:50 PM, Dave wrote:
> I tried a 40M OCFD for a while. I gave up on it and went back to a
> centre fed dipole instead.
>
> >
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Elecraft mailing list

Re: A Good Antenna Length?

In reply to this post by Dave-5

I have always found the the OCF antennas require a sufficient amount of feedline to mask the weird impedances it has. I have successfully used 135 foot 33% offset fed 4:1 balun with W1JR choke and >100 feet of coax necessary. I tried to use 22 feet and it was a total loss. All with <100 watts of course like Jim suggests. The added length does not add enough loss to account for the change.

Mel, K6KBE

On Saturday, July 5, 2014 9:50 AM, Dave <[hidden email]> wrote:

I tried a 40M OCFD for a while. I gave up on it and went back to a centre
fed dipole instead.

Even on 40M it didn't seem very good and I was plagued with RF getting into
PCs and them shutting down or periferals stopping working. Plus, despite
the hype, it didn't really seem to work well on other bands. The Antenna
analyser was very dismissive, showing resonances outside of the Amateur
bands and, on some that it was supposed to work on, no sign of any resonance
at all.

Dave (G0DJA)

----- Original Message -----
From: "Jim Brown" <[hidden email]>
To: <[hidden email]>
Sent: Saturday, July 05, 2014 2:24 PM
Subject: Re: [Elecraft] A Good Antenna Length?

Dave-5

Re: A Good Antenna Length?

In reply to this post by Elecraft mailing list

I was using QRP, 3 Watts from the KX3, and I tend to use less than 5W CW on most bands.

Even on receive it performed poorly, which is why I wnt back to a dipole.

Cheers - Dave (G0DJA)
----- Original Message -----
To: Dave ; [hidden email]
Sent: Saturday, July 05, 2014 5:10 PM
Subject: Re: [Elecraft] A Good Antenna Length?

Off center fed dipoles, Windoms and end fed half waves are primarily low power if not QRP antennas where you can do poorly with any antenna. They are prone to arcing, heating and RF where you don't want it. You are better off with conventional low radiation resistance antennas if you plan to use 100 watts or higher. The search for an antenna that will make QRP sound like a kilowatt is futile. The only way to do that is to have excellent conditions and infinite patience which will make anything sort of work.

Willis 'Cookie' Cooke, TDXS DX Chairman
K5EWJ & Trustee N5BPS, USS Cavalla, USS Stewart
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David Cutter

Re: A Good Antenna Length?

In reply to this post by Jim Brown-10

Rick DJ0IP has performed many hundreds of cmc measurements over the last
year or so. He has yet to publish his complete findings but here is a
taste:
http://www.dj0ip.de/cmc-test/
http://www.dj0ip.de/cmc-test/the-components/the-baluns/
http://www.dj0ip.de/cmc-test/pre-test-preparation/
http://www.dj0ip.de/cmc-test/results-test-data/ant-1-b0/
http://www.dj0ip.de/cmc-test/test-configurations/
http://www.dj0ip.de/cmc-test/results-test-data/ant-2-b5/

After many hundreds of measurements he has demonstrated that with a *dual
core* Guanella 4:1 balun at the feed point, common mode current can be tamed
even with deliberately poor antenna and feeder layout.

There are not many folks who would take the care and have the patience to do
this sort of work.

David
G3UNA

----- Original Message -----
From: "Jim Brown" <[hidden email]>
To: <[hidden email]>
Sent: Saturday, July 05, 2014 3:24 PM
Subject: Re: [Elecraft] A Good Antenna Length?

> On 7/5/2014 2:05 AM, David Cutter wrote:
>> You might consider an off-centre-fed dipole with appropriate balun and
>> choke.
>
> Not if you're going to run power. An off center fed antenna generates high
> common mode voltage, which will fry even the best choke when running
> power. I wouldn't consider such an antenna at greater than 100W.
>
> 73, Jim K9YC

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Dick, K2ZR

Re: A Good Antenna Length?

Where can I find the results comparing these 4 antennas?
http://www.dj0ip.de/cmc-test/the-antennas/
Thanks and 73,
Dick, K2ZR
-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of David
Cutter
Sent: Saturday, July 05, 2014 1:30 PM
To: [hidden email]; [hidden email]
Subject: Re: [Elecraft] A Good Antenna Length?

Rick DJ0IP has performed many hundreds of cmc measurements over the last
year or so. He has yet to publish his complete findings but here is a
taste:
http://www.dj0ip.de/cmc-test/
http://www.dj0ip.de/cmc-test/the-components/the-baluns/
http://www.dj0ip.de/cmc-test/pre-test-preparation/
http://www.dj0ip.de/cmc-test/results-test-data/ant-1-b0/
http://www.dj0ip.de/cmc-test/test-configurations/
http://www.dj0ip.de/cmc-test/results-test-data/ant-2-b5/

After many hundreds of measurements he has demonstrated that with a *dual
core* Guanella 4:1 balun at the feed point, common mode current can be tamed
even with deliberately poor antenna and feeder layout.

There are not many folks who would take the care and have the patience to do
this sort of work.

David
G3UNA

----- Original Message -----
From: "Jim Brown" <[hidden email]>
To: <[hidden email]>
Sent: Saturday, July 05, 2014 3:24 PM
Subject: Re: [Elecraft] A Good Antenna Length?

> On 7/5/2014 2:05 AM, David Cutter wrote:
>> You might consider an off-centre-fed dipole with appropriate balun and
>> choke.
>
> Not if you're going to run power. An off center fed antenna generates high

> common mode voltage, which will fry even the best choke when running
> power. I wouldn't consider such an antenna at greater than 100W.
>
> 73, Jim K9YC

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LA7NO

Re: A Good Antenna Length?

Try here: http://www.dj0ip.de/cmc-test/results-test-data/

P-T

On 5 July 2014 20:45, Dick, K2ZR <[hidden email]> wrote:

> Where can I find the results comparing these 4 antennas?
> http://www.dj0ip.de/cmc-test/the-antennas/
> Thanks and 73,
> Dick, K2ZR
> -----Original Message-----
> From: Elecraft [mailto:[hidden email]] On Behalf Of David
> Cutter
> Sent: Saturday, July 05, 2014 1:30 PM
> To: [hidden email]; [hidden email]
> Subject: Re: [Elecraft] A Good Antenna Length?
>
> Rick DJ0IP has performed many hundreds of cmc measurements over the last
> year or so. He has yet to publish his complete findings but here is a
> taste:
> http://www.dj0ip.de/cmc-test/
> http://www.dj0ip.de/cmc-test/the-components/the-baluns/
> http://www.dj0ip.de/cmc-test/pre-test-preparation/
> http://www.dj0ip.de/cmc-test/results-test-data/ant-1-b0/
> http://www.dj0ip.de/cmc-test/test-configurations/
> http://www.dj0ip.de/cmc-test/results-test-data/ant-2-b5/
>
>
> After many hundreds of measurements he has demonstrated that with a *dual
> core* Guanella 4:1 balun at the feed point, common mode current can be tamed
> even with deliberately poor antenna and feeder layout.
>
> There are not many folks who would take the care and have the patience to do
> this sort of work.
>
> David
> G3UNA
>
>
>
>
>
>
> ----- Original Message -----
> From: "Jim Brown" <[hidden email]>
> To: <[hidden email]>
> Sent: Saturday, July 05, 2014 3:24 PM
> Subject: Re: [Elecraft] A Good Antenna Length?
>
>
>> On 7/5/2014 2:05 AM, David Cutter wrote:
>>> You might consider an off-centre-fed dipole with appropriate balun and
>>> choke.
>>
>> Not if you're going to run power. An off center fed antenna generates high
>
>> common mode voltage, which will fry even the best choke when running
>> power. I wouldn't consider such an antenna at greater than 100W.
>>
>> 73, Jim K9YC
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>
> ______________________________________________________________
> Elecraft mailing list
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>
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> Message delivered to [hidden email]

73,

Per-Tore / LA7NO

Barry K3NDM

Re: A Good Antenna Length?

In reply to this post by Jim Brown-10

Jim,
What you say can be correct. However, this need not happen all the time. When common mode issues arise one of the problems is that the wrong type of balun was chosen. Voltage baluns suffer when the VSWR gets too high. What you really need to use on these types of antennas is a current type balun. They have less of a problem than do the voltage type.

I use a Carolina Windom here. That means I use a voltage type balun at the feed point, deliberately causing radiation from the shield of the vertical section of feed coax. 18 feet bellow the antenna feed point I place a 1:1 current balun, an RF choke, to prevent common mode problems. I have not had problems with common mode currents with this arrangement, and it will work at higher powers than the 100 Watts I normally use so long as the baluns and coax are rated for the power level you plan to run.

73,
Barry
K3NDM

----- Original Message -----

From: "jim" <[hidden email]>
To: "elecraft" <[hidden email]>
Sent: Saturday, July 5, 2014 10:24:19
Subject: Re: [Elecraft] A Good Antenna Length?

On 7/5/2014 2:05 AM, David Cutter wrote:
> You might consider an off-centre-fed dipole with appropriate balun and
> choke.

Not if you're going to run power. An off center fed antenna generates
high common mode voltage, which will fry even the best choke when
running power. I wouldn't consider such an antenna at greater than 100W.

73, Jim K9YC
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Guy Olinger K2AV

Re: A Good Antenna Length?

In reply to this post by Elecraft mailing list

An end-fed half wave inverted L (EFHWL) done properly works very well. It
needs to be tuned at the base of the wire against ground.

An EFHWL for 80m is an excellent antenna that has no nulls and has
vertically polarized low angle radiation equal to a decent 1/4 wave
vertical. The horizontal wire fills in the general pattern to a hemisphere
with a broad and mild null in the direction of the horizontal pull. It is
an ideal all-distance contest antenna, because there are no holes in
coverage in any direction or elevation.

I have used this antenna at 1.5 kW off and on across 50 years with
excellent results. The current max is at the bend, with a high resistance
feed at the ground, making the effective series resistance of the grounding
system of no consequence. Even a completely pathetic 100 ohm ground at the
base does little damage against a 1000-2000-3000 ohm feedpoint for the
wire.

It IS uncommon and requires tuning at the base of the antenna, and that
network requires components usually found in the output tuning networks of
tube based QRO amplifiers. You can't feed the base of the antenna directly
from coax without a tuner, and you can't buy the tuner off the shelf
anywhere.

With some DPST relays, coil stock and a single well-chosen fixed value QRO
transmit capacitor, the antenna + tuning mechanism can cover the entire
3.5-4 ham band with less than 1.5:1 SWR anywhere.

With some further work in the tuning mechanism, and attention to a proper
160m counterpoise, the wire will work well on 160-80-40-30 with distance
from any tower(s).

In my experience with that over the years, the EFHWL always beat an 80
dipole or inverted vee for DX and was as good as or beat dipole and vee for
local and mid range. A 4-square would beat the EFHWL for DX.

73, Guy.

On Sat, Jul 5, 2014 at 1:10 PM, WILLIS COOKE via Elecraft <
[hidden email]> wrote:

> Off center fed dipoles, Windoms and end fed half waves are primarily low
> power if not QRP antennas where you can do poorly with any antenna.
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riese-k3djc

Re: A Good Antenna Length?

In reply to this post by Jim GM

Hi Guy

same thing here I was going to use it on 160 but really like 75
makes a good DX antenna and when the band is open I have
no problems breaking pileups,,, up 40 Ft and out ? Horz
works OK on all other harmonic related bands ,,, did run some tests with
a station 30 miles from me. I used to use a tuner at the base but I find
the
HB antenna tuner in the shack works well ,,,So what the heck ,,, Use a
series of ferrites on the
coax feed and run the feed about 50 Ft through the basement to the shack
not a QRP antenna ? use a Heath amp drive it wit a K3
bottom line
put up some wire and get on the air

Bob K3DJC

On Sat, 5 Jul 2014 16:08:19 -0400 Guy Olinger K2AV <[hidden email]>
writes:

> An end-fed half wave inverted L (EFHWL) done properly works very
> well. It
> needs to be tuned at the base of the wire against ground.
>
> An EFHWL for 80m is an excellent antenna that has no nulls and has
> vertically polarized low angle radiation equal to a decent 1/4 wave
> vertical. The horizontal wire fills in the general pattern to a
> hemisphere
> with a broad and mild null in the direction of the horizontal pull.
> It is
> an ideal all-distance contest antenna, because there are no holes
> in
> coverage in any direction or elevation.

Eric Swartz - WA6HHQ

Re: A Good Antenna Length?

Administrator

We are well past the posting limit for a single topic. Let's give this one a rest for now.

73,
Eric
List Moderator etc.
elecraft.com
---
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Jim GM

Re: A Good Antenna Length?

In reply to this post by Jim GM

Thank you for all the input.

Antennas are a fun thing to talk about and something every one seams to
enjoy and building their own, like I do. I had many wires antennas in the
last 46 years. I am still learning. One thing I have not done is get a
computer program for my Apple Computer and an antenna analyzer with
software for it. So I do every thing trial and error.

So far I found that the KX3 and KXPA100 internal tuner seams to be as good
or better than the MFJ 989B that I had for many years. there were 2 tuners
that were as good or better than this back in the day. Tuners have not
changed much since then except for the introduction of auto tuners. I have
a MFJ 998RT that I blew up on 160M with 500 watts MFJ replaced it for free.
They shipped me a new one and I have not even opened the box.

With that said, I have been searching for that antenna that will tune 160-6
meters and found out on this forum it does not exist. I never attempted to
do this type of search. I now know why Wayne had stated that in Digest 123
Issue 6 about 3rd harmonics on the same coax. Jim Borwn comments are words
of wisdom to stand by.

I try to stay away from baluns as much as possible. Hairpin matches seams
to be the best route, and I had proved that with tests on and spots on RBN.

I have to go to work now and will be gone for a couple of days and I know I
can add more to this. Took me a while to go through all the comments, and I
had forgotten some of them. so my apologies for not mentioning them.

Thank you for all your help.

--
Jim K9TF
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