On higher HF and 6M simply winding all the turns in one direction adds a lot
of capacitance which defeats the effectiveness.
Using RG-142 or RG-303 has been popular for decades on these toroids. Wind
half the turns in one direction, then cross the toroid and reverse for the
next half.
There is a lot more to using ferrites at RF than at DC and audio. Without
adequate test equipmenand understanding the procedures required it is often
very misleading.
Anyone still having a RadioKit catalog from the 1986-90 era will find a
wealth of data that I wrote on using ferrites at RF.
Carl
KM1H
Carl KM1H
----- Original Message -----
From: "Mark" <n2qt@verizon.net>
To: <towertalk@contesting.com>
Sent: Wednesday, July 25, 2007 9:28 PM
Subject: Re: [TowerTalk] Ferrite beads for common mode current
> 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
>>>
>>>
>>> _______________________________________________
>>>
>>>
>>>
>>> _______________________________________________
>>> TowerTalk mailing list
>>> TowerTalk@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk@contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
>
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|