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Re: [Amps] (Perhaps) A plate choke too far ...

To: Radio WC6W <wc6w_amps@yahoo.com>
Subject: Re: [Amps] (Perhaps) A plate choke too far ...
From: Larry <larry@w7iuv.com>
Date: Thu, 14 Jan 2010 10:12:42 -0800
List-post: <amps@contesting.com">mailto:amps@contesting.com>
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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