I've used RG142 which is Teflon insulated for high power use but still
small in diameter (like rg58).
I find that cutting the jacket off allows it to bend enough to fit a 2.4 in
toroid pretty easily. I dip
the completed assembly in the dip-it plastic stuff (normally used to put
grips on tools) to seal it.
Mark n2qt
----- Original Message -----
From: "jeremy-ca" <km1h@jeremy.mv.com>
To: <n7ka@comcast.net>; "TowerTalk" <towertalk@contesting.com>; "Jim Lux"
<jimlux@earthlink.net>
Sent: Wednesday, July 25, 2007 9:05 PM
Subject: Re: [TowerTalk] Ferrite beads for common mode current
> It aint easy getting 5 turns of RG-213 thru a 2.4" OD dia toroid!
> The definitve tests for Fairite 43 Mix beads as a sleeve balun was done in
> the early 80's and published in Scuttlebut and most likely reprinted
> elsewhere.
>
> Carl
> KM1H
>
>
>
> ----- Original Message -----
> From: "Jim Lux" <jimlux@earthlink.net>
> To: <n7ka@comcast.net>; "TowerTalk" <towertalk@contesting.com>
> Sent: Wednesday, July 25, 2007 8:12 PM
> Subject: Re: [TowerTalk] Ferrite beads for common mode current
>
>
>> At 01:58 PM 7/25/2007, n7ka@comcast.net wrote:
>>>Getting ready to install another 6M yagi here and building another
>>>for a friend. Want to use a choke on the feed line which will be
>>>either RG-213 (MIL-C-17 compliant) or on LMR-400UF (super flex). In
>>>all cases I want the capability for 1500W. I do not like the idea
>>>of additional connectors so my plan is to but the beads on the line
>>>at feedpoint of the cable that goes down to the hardline just below
>>>the top of the tower. Would Fair-Rite 2643102002 be the correct
>>>choice? The id at 0.505 inch is large enough to fit over the
>>>RG-213/LMR-400. Or do I need another mix and how many beads.
>>
>>
>> You can also use a larger diameter toroid and run multiple turns of
>> your coax through it. The inductance of the choke goes as the square
>> of the number of turns, so 5 turns through one core is like 25 cores
>> in a row (in an ideal world... there's capacitance and leakage L...
>> but still... )
>>
>>
>> Jim Brown's website http://www.audiosystemsgroup.com/ has a paper on
>> various ways to make RF chokes for feedlines (among other things)
>> with measured data over a wide range of frequencies. It's that
>> RFI-Ham pdf file referenced in recent posts. 5 turns on a #31 2.4
>> inch core looks like around 1Kohm Z.. (see page 12) page 28 has a
>> photo of a mondo choke. I use one very similar to this for
>> connecting a network analyzer to antennas (except I use smaller coax).
>>
>> Jim, W6RMK
>>
>>
>> _______________________________________________
>>
>>
>>
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>
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