Hi Larry,
>Why 1-2 mH?
So that the choke still behaves as a choke down on 160 rather than becoming a
significant portion of the plate circuit.
73 & Good morning,
Marv WC6W
http://wc6w.50webs.com/
--- On Thu, 1/14/10, Larry <larry@w7iuv.com> wrote:
> From: Larry <larry@w7iuv.com>
> Subject: Re: [Amps] (Perhaps) A plate choke too far ...
> To: "Radio WC6W" <wc6w_amps@yahoo.com>
> Cc: amps@contesting.com
> Date: Thursday, January 14, 2010, 10:12 AM
> 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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