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Re: [Amps] RF Chokes

To: "'Kenneth D. Grimm, K4XL'" <kgrimm@adelphia.net>, <wc6w@juno.com>
Subject: Re: [Amps] RF Chokes
From: "Harold Mandel" <ka1xo@juno.com>
Date: Wed, 19 Jul 2006 09:31:48 -0400
List-post: <mailto:amps@contesting.com>
Yesterday, W1ITT mentioned his chokes are hollow Teflon, filled
with a "particular" ferrite filling.

I wonder if the use of the word "particular" refers to the 
meaning "particle-matter," or " a specific variety?"


In asking this, does anyone have experience with ferrite powders
filling such devices? Is it possible to formulate a ferrite core
starting with powder and something like a chemical eutectic?

Can just ferrite powder without a binder work?

Hal
W4HBM


-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Kenneth D. Grimm, K4XL
Sent: Wednesday, July 19, 2006 9:09 AM
To: wc6w@juno.com
Cc: philc@texascellnet.com; amps@contesting.com
Subject: Re: [Amps] RF Chokes

wc6w@juno.com wrote:
>> -- "Phil Clements" <philc@texascellnet.com> wrote:
>>     
> <snip>
>
>   
>> Harris has been doing this for years in their amps. The RF->110, 
>> (pair of 4CX1500B's) has a plate choke that is a very small ferrite 
>> loaded unit that is clean from 1.8-30 mhz. This was the ideal fix 
>> for adding WARC bands and 160 meters, but the amateur amp 
>> manufacturers did not pick up on this.
>>
>> <snip>
>>
>>     
>> (((73)))
>> Phil Clements, K5PC
>>     
>
>   

Would it be possible to have a look at the photos that you took of the 
choke and parasitic suppressor arrangement that you posted on  
www.pixhost.com/pixp/philk5pc/Platechoke.jpg but which are no longer 
available?

> Hi Phil,
>   If I recall correctly, that choke is listed on the schematic at 
> 115uH.
>
>   Employing the ferrite core should place the first (parallel) 
> resonance suitably above 30 MHz.
>
>   This appears to be a valid approach because of the low plate 
> impedance (circa 1000 ohms).  Though there will still be plenty of 
> reactive current through that choke on the lowest bands.
>
>   Still a compromise, albeit a less objectionable one than 
> most "amateur" amps.
>
>   I'm feeling just a bit of deja vu all over again. :-)
>   To see why, start at this old link:
>
>    http://lists.contesting.com/_amps/2000-03/msg00603.html
>
> 73 & Good evening,
>   Marv WC6W
>
> http://wc6w.50webs.com/
>
>   
Actually, it makes pretty good reading...all over again.   ;-) 


73,
-- 

Ken K4XL
k4xl@arrl.net

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