Insulation thickness comes into play here. A heavy double Formvar or other
high heat/voltage coating can add to the apparent size.
Carl
KM1H
----- Original Message -----
From: "James Colville" <jimw7ry@gmail.com>
To: "Jim Thomson" <Jim.thom@telus.net>
Cc: <amps@contesting.com>
Sent: Saturday, January 16, 2010 10:36 PM
Subject: Re: [Amps] KK5DR's ferrite loaded plate chokes.
>I just wound an ameritron look alike with #28. It's larger than they use. I
> have an original ameritron choke to compare with. I think they must use
> #29.
>
> My resistance was lower using #28 and it was less uH.
>
> 73
> Jim W7RY
>
>
>
> On Sat, Jan 16, 2010 at 6:59 PM, Jim Thomson <Jim.thom@telus.net> wrote:
>
>> I Checked a bunch of really old e-mail, and notes. The folk's who
>> duplicated the KK5DR plate choke, using 1/2" type 43 rod, stuffed into
>> the
>> inside of a hollowed out 1" OD Teflon rod
>> had nothing but grief. All the rods overheated ! In some cases, the
>> rod actually launched itself out the top !
>>
>> Either 1" type 43 rod is required, [like several type 43, 1" Od
>> beads slid over the 1/2" rod].... or several type 43 rods bundled
>> together.
>>
>> Perhaps type 43 material is the wrong stuff to be using for a plate
>> choke...esp considering the typ plate load Z's involved ??
>>
>> Type 43.... 1" OD bead's, slid over 393 Teflon coax makes for
>> excellent Choke baluns. The 1/2" x 8" long type 43 rods work
>> great
>> for Bifilar's. But in both those cases,
>> the Z is only 25-50 ohms.
>>
>> What would be an excellent solution, would be a higher current version
>> of
>> the RF parts /Ameritron plate choke. I have asked a few times what ga
>> wire is used in the Ameritron choke,
>> and can't get a straight answer. I believe it's around 28 ga. A
>> version made with 22 ga wire would be the ultimate solution. I know
>> how
>> Tom designed the Ameritron choke.
>> However, I'm not prepared to sit there in the shop for months, with a
>> vna, etc, trying to park resonances. The 2 x choke + relay version
>> was a cheap way to get around the problem.
>> Incidentally, the choke relay coil was activated by a 3rd wafer on the
>> tuned input switch.
>>
>> Later.... Jim VE7RF
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>>
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