There was an article in HRM in the early 80's showing a 5kw rated choke with
a rod. I tried several iterations and all smoked at some frequency at 1200W.
The subject came up again on here, I believe, a few years ago with someone
claiming it works.
Carl
KM1H
----- Original Message -----
From: "Larry" <larry@w7iuv.com>
To: "Radio WC6W" <wc6w_amps@yahoo.com>
Cc: <amps@contesting.com>
Sent: Thursday, January 14, 2010 1:12 PM
Subject: Re: [Amps] (Perhaps) A plate choke too far ...
> Marv & all,
>
> Just some random thoughts which may or may not be appropriate/valid:
>
> Why 1-2 mH? Just curious because if I had a choke design that was
> 250-300 MICRO H and didn't have any resonances below 30 MHz I would be a
> very happy camper.
>
> Several years ago there was a discussion on this list regarding ferrite
> used in plate chokes. I don't remember all of the conclusions but I do
> remember some examples in commercial TX's. Seems like they used a
> rod/slug *partially* inserted into the solenoid choke.
>
> Re the referenced web page, seems like there are some errors there but
> the end result looks interesting. I would like to measure one of those
> myself as I don't trust most guys to get it right.
>
> Having tried the grid dip meter approach myself, I found that was a good
> way to wind up with all the magic smoke escaping the choke in question.
> Just today while measuring the loaded Q of a pi-net in the latest amp
> project, I was able to see and read out the choke resonance to within a
> kHz or so while actually in the sealed up amp and tuned to 10/12 meters.
> I use a VNA for this but can and have used a sig gen and spectrum
> analyzer with equal success.
>
> My normal solution to the choke problem is the restrict the number of
> bands the amp covers. Mono-band amps are the best!
>
> 73, Larry
>
> Larry - W7IUV
> DN07dg
> http://w7iuv.com
>
> Radio WC6W wrote:
>> Hi Angel,
>> The point was to make a rather high value (1-2mHy) choke with no
>> resonances in the HF region.
>>
>> The saturation gotcha was a by-product.
>>
>> A rod wouldn't suffice in this application. A gapped core might. The
>> gap would need to be only a few thousand's wide and I don't have a
>> diamond saw like that... Too bad pot cores aren't made in 43.
>>
>> 73 & Good morning,
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