[Amps] RF Chokes

[Kenneth D. Grimm, K4XL]

wc6w at juno.com wrote:
>> -- "Phil Clements" <philc at 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 at arrl.net

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