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Coiled Coax Choke

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Edward A. Dauer

Coiled Coax Choke

I am thinking of adding a coiled coax common-mode choke to my system.
Presently it goes K3-KPA500-KAT500 then 100 ft coax to the base of an
inverted Vee¹s center support pole (collapsible fiberglass), then 30 feet
up the pole to a 1:1 balun feeding a fanned 10-15-20 Vee. The idea, for a
couple of reasons, is to put the choke at the base of the pole, something
I haven¹t seen discussed in the literature. Two questions I am wondering
about: 1. The choke would be 100 feet from the tuner and about 25 feet
from the antenna/balun. Probably not as good as having it right at the
Vee, but is that compromise worth while? 2. For appearance sake I am
thinking about winding the coax around the base of the support pole. It
is 2 inches in diameter but I could slip a 3 inch PVC over that section to
increase the diameter. Anyone know an algorithm for determining the
number of turns in the winding if I do that? I would be much obliged for
any thoughts and suggestions . . . Tnx!

Ted, KN1CBR

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k6dgw

Re: Coiled Coax Choke

On 10/20/2014 7:28 PM, Dauer, Edward wrote:

> I am thinking of adding a coiled coax common-mode choke to my system.
> Presently it goes K3-KPA500-KAT500 then 100 ft coax to the base of an
> inverted Vee¹s center support pole (collapsible fiberglass), then 30 feet
> up the pole to a 1:1 balun feeding a fanned 10-15-20 Vee. The idea, for a
> couple of reasons, is to put the choke at the base of the pole, something
> I haven¹t seen discussed in the literature.

Are you having common-mode RF problems in your shack?

Two questions I am wondering
> about: 1. The choke would be 100 feet from the tuner and about 25 feet
> from the antenna/balun. Probably not as good as having it right at the
> Vee, but is that compromise worth while?

Maybe, every installation is unique.

2. For appearance sake I am
> thinking about winding the coax around the base of the support pole. It
> is 2 inches in diameter but I could slip a 3 inch PVC over that section to
> increase the diameter.

If you're having RFITS problems ["RF In The Shack"], there are better
and far less visually obvious ways to suppress that using common mode
ferrite chokes than winding up your coax around anything. If you don't
have RFITS problems, "nothing" might be the best course of action

> Anyone know an algorithm for determining the
> number of turns in the winding if I do that?

Air inductor equations are in the ARRL Handbook and ARRL Antenna Book.
If you really need to do this, I'll suggest you look at the publications
from Jim, K9YC, at audiosystems.com first ... he pretty well has this
subject knocked.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2015 Cal QSO Party 3-4 Oct 2015
- www.cqp.org

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Jim Brown-10

Re: Coiled Coax Choke

In reply to this post by Edward A. Dauer

On 10/20/2014 7:28 PM, Dauer, Edward wrote:
> I am thinking of adding a coiled coax common-mode choke to my system.

Although it's all over the literature, a coil of coax is NOT an
effective common mode choke. I've discussed this at length in
k9yc.com/RFI-Ham.pdf

What do you mean by "antenna/balun?" The word "balun" describes at least
a dozen different things. What problem are you trying to solve?

73, Jim K9YC
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ve3dvy

Re: Coiled Coax Choke

In reply to this post by Edward A. Dauer

You say a 1:1 balun. What type is it and should it not be preventing
common mode currents? If not Id consider one that will rather than
adding a choke. I bought a commercial 1:1 Balun opened it up and found
it to be just a length of RG8X looped once inside the casing with half a
dozen ferrites around it. What I have done is have ground rods at the
base of the pole. I am using a 10-80 +warc fan dipole that looks a
little like a flattened spider web supported with guyed camouflage tent
poles to about 40 ft I have 6 ferrites on the coax at the feed the
ones I got out of the commercial balun. Then at the base I have several
5 ft copper pipes driven into the ground around the pole about 5 ft
apart all bonded together with 6 gauge bare copper that is also burred
a few inched below the surface safe from the lawn mower. I have a
barrel connector at the base that lets me connect the shield to this
ground I have no common mode issues. at least I have not experienced
any.

David VE3SD

On 10/20/2014 22:28, Dauer, Edward wrote:

> I am thinking of adding a coiled coax common-mode choke to my system.
> Presently it goes K3-KPA500-KAT500 then 100 ft coax to the base of an
> inverted Vee¹s center support pole (collapsible fiberglass), then 30 feet
> up the pole to a 1:1 balun feeding a fanned 10-15-20 Vee. The idea, for a
> couple of reasons, is to put the choke at the base of the pole, something
> I haven¹t seen discussed in the literature. Two questions I am wondering
> about: 1. The choke would be 100 feet from the tuner and about 25 feet
> from the antenna/balun. Probably not as good as having it right at the
> Vee, but is that compromise worth while? 2. For appearance sake I am
> thinking about winding the coax around the base of the support pole. It
> is 2 inches in diameter but I could slip a 3 inch PVC over that section to
> increase the diameter. Anyone know an algorithm for determining the
> number of turns in the winding if I do that? I would be much obliged for
> any thoughts and suggestions . . . Tnx!
>
> Ted, KN1CBR
>
> ______________________________________________________________
> 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
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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Michael Walker

Re: Coiled Coax Choke

David

What mix of ferrites are you using?

Mike va3mw

On Tue, Oct 21, 2014 at 8:29 AM, david Moes <[hidden email]> wrote:

> You say a 1:1 balun. What type is it and should it not be preventing
> common mode currents? If not Id consider one that will rather than adding
> a choke. I bought a commercial 1:1 Balun opened it up and found it to be
> just a length of RG8X looped once inside the casing with half a dozen
> ferrites around it. What I have done is have ground rods at the base of
> the pole. I am using a 10-80 +warc fan dipole that looks a little like a
> flattened spider web supported with guyed camouflage tent poles to about 40
> ft I have 6 ferrites on the coax at the feed the ones I got out of the
> commercial balun. Then at the base I have several 5 ft copper pipes driven
> into the ground around the pole about 5 ft apart all bonded together with
> 6 gauge bare copper that is also burred a few inched below the surface
> safe from the lawn mower. I have a barrel connector at the base that lets
> me connect the shield to this ground I have no common mode issues. at
> least I have not experienced any.
>
>
> David VE3SD
>
> On 10/20/2014 22:28, Dauer, Edward wrote:
>
>> I am thinking of adding a coiled coax common-mode choke to my system.
>> Presently it goes K3-KPA500-KAT500 then 100 ft coax to the base of an
>> inverted Vee¹s center support pole (collapsible fiberglass), then 30 feet
>> up the pole to a 1:1 balun feeding a fanned 10-15-20 Vee. The idea, for a
>> couple of reasons, is to put the choke at the base of the pole, something
>> I haven¹t seen discussed in the literature. Two questions I am wondering
>> about: 1. The choke would be 100 feet from the tuner and about 25 feet
>> from the antenna/balun. Probably not as good as having it right at the
>> Vee, but is that compromise worth while? 2. For appearance sake I am
>> thinking about winding the coax around the base of the support pole. It
>> is 2 inches in diameter but I could slip a 3 inch PVC over that section to
>> increase the diameter. Anyone know an algorithm for determining the
>> number of turns in the winding if I do that? I would be much obliged for
>> any thoughts and suggestions . . . Tnx!
>>
>> Ted, KN1CBR
>>
>> ______________________________________________________________
>> 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
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>>
>>
> ______________________________________________________________
> 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
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

ve3dvy

Re: Coiled Coax Choke

what ever it was in the balun I purchased and took apart so Im not sure.

David Moes
President: Peterborough Amateur Radio Club.
[hidden email]
VE3DVY, VE3SD

On 10/21/2014 09:49, Michael Walker wrote:

> David
>
> What mix of ferrites are you using?
>
> Mike va3mw
>
>
> On Tue, Oct 21, 2014 at 8:29 AM, david Moes <[hidden email]> wrote:
>
>> You say a 1:1 balun. What type is it and should it not be preventing
>> common mode currents? If not Id consider one that will rather than adding
>> a choke. I bought a commercial 1:1 Balun opened it up and found it to be
>> just a length of RG8X looped once inside the casing with half a dozen
>> ferrites around it. What I have done is have ground rods at the base of
>> the pole. I am using a 10-80 +warc fan dipole that looks a little like a
>> flattened spider web supported with guyed camouflage tent poles to about 40
>> ft I have 6 ferrites on the coax at the feed the ones I got out of the
>> commercial balun. Then at the base I have several 5 ft copper pipes driven
>> into the ground around the pole about 5 ft apart all bonded together with
>> 6 gauge bare copper that is also burred a few inched below the surface
>> safe from the lawn mower. I have a barrel connector at the base that lets
>> me connect the shield to this ground I have no common mode issues. at
>> least I have not experienced any.
>>
>>
>> David VE3SD
>>
>> On 10/20/2014 22:28, Dauer, Edward wrote:
>>
>>> I am thinking of adding a coiled coax common-mode choke to my system.
>>> Presently it goes K3-KPA500-KAT500 then 100 ft coax to the base of an
>>> inverted Vee¹s center support pole (collapsible fiberglass), then 30 feet
>>> up the pole to a 1:1 balun feeding a fanned 10-15-20 Vee. The idea, for a
>>> couple of reasons, is to put the choke at the base of the pole, something
>>> I haven¹t seen discussed in the literature. Two questions I am wondering
>>> about: 1. The choke would be 100 feet from the tuner and about 25 feet
>>> from the antenna/balun. Probably not as good as having it right at the
>>> Vee, but is that compromise worth while? 2. For appearance sake I am
>>> thinking about winding the coax around the base of the support pole. It
>>> is 2 inches in diameter but I could slip a 3 inch PVC over that section to
>>> increase the diameter. Anyone know an algorithm for determining the
>>> number of turns in the winding if I do that? I would be much obliged for
>>> any thoughts and suggestions . . . Tnx!
>>>
>>> Ted, KN1CBR
>>>
>>> ______________________________________________________________
>>> 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
>>> Please help support this email list: http://www.qsl.net/donate.html
>>> Message delivered to [hidden email]
>>>
>>>
>> ______________________________________________________________
>> 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
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>>
> ______________________________________________________________
> 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
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Edward A. Dauer

Coiled coax choke

In reply to this post by Edward A. Dauer

Thanks to all who replied to my coiled-coax choke question. Good ideas,
all; and I am off to study what K9YC has written on the subject . . .

73, Ted KN1CBR

>
>
>
>------------------------------
>
>Message: 6
>Date: Mon, 20 Oct 2014 19:48:29 -0700
>From: Walter Underwood <[hidden email]>
>To: "[hidden email]" <[hidden email]>
>Subject: Re: [Elecraft] Coiled Coax Choke
>Message-ID: <[hidden email]>
>Content-Type: text/plain; charset=windows-1252
>
>A choke in the middle of the transmission line could help, but the usual
>configuration is a current balun at the antenna to reject common-mode
>signals at the source, plus an optional choke at the entrance to the
>shack to reject noise picked up by the outside of the coax shield.
>
>A coiled-coax choke works OK, but you get the best rejection from a
>toroid-based choke or balun. I?ve had good results with the ones from
>Balun Designs (http://www.balundesigns.com).
>
>Putting a Balun Designs balun at my dipole dropped the noise by 6dB.
>
>I highly recommend K9YC?s super-detailed explanation of fighting noise in
>your antenna and elsewhere in your shack.
>
>http://audiosystemsgroup.com/RFI-Ham.pdf
>
>wunder
>K6WRU
>
>
>------------------------------
>
>Message: 8
>Date: Mon, 20 Oct 2014 20:31:35 -0700
>From: Jim Brown <[hidden email]>
>To: [hidden email]
>Subject: Re: [Elecraft] Coiled Coax Choke
>Message-ID: <[hidden email]>
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>On 10/20/2014 7:28 PM, Dauer, Edward wrote:
>> I am thinking of adding a coiled coax common-mode choke to my system.
>
>Although it's all over the literature, a coil of coax is NOT an
>effective common mode choke. I've discussed this at length in
>k9yc.com/RFI-Ham.pdf
>
>What do you mean by "antenna/balun?" The word "balun" describes at least
>a dozen different things. What problem are you trying to solve?
>
>73, Jim K9YC
>
>
>
>------------------------------
>
>Message: 12
>Date: Tue, 21 Oct 2014 08:29:38 -0400
>From: david Moes <[hidden email]>
>To: [hidden email]
>Subject: Re: [Elecraft] Coiled Coax Choke
>Message-ID: <[hidden email]>
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>You say a 1:1 balun. What type is it and should it not be preventing
>common mode currents? If not Id consider one that will rather than
>adding a choke. I bought a commercial 1:1 Balun opened it up and found
>it to be just a length of RG8X looped once inside the casing with half a
>dozen ferrites around it. What I have done is have ground rods at the
>base of the pole. I am using a 10-80 +warc fan dipole that looks a
>little like a flattened spider web supported with guyed camouflage tent
>poles to about 40 ft I have 6 ferrites on the coax at the feed the
>ones I got out of the commercial balun. Then at the base I have several
>5 ft copper pipes driven into the ground around the pole about 5 ft
>apart all bonded together with 6 gauge bare copper that is also burred
>a few inched below the surface safe from the lawn mower. I have a
>barrel connector at the base that lets me connect the shield to this
>ground I have no common mode issues. at least I have not experienced
>any.
>
>