[Elecraft] Coiled Coax Choke

[Michael Walker]

David

What mix of ferrites are you using?

Mike va3mw


On Tue, Oct 21, 2014 at 8:29 AM, david Moes <dmoes at nexicom.net> 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
>>
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