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[AMPS] don't choke on this

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Subject: [AMPS] don't choke on this
From: (Rich Measures)
Date: Tue, 31 Mar 98 10:28:26 -0800
>On Mon, 30 Mar 1998 17:10:39 -0700 John Lyles <> writes:
>>I apologize to you ham amplifier designers as your frequency range is 
>>soooo broad. Bound to hit a sneak resonance if you're not careful, not to 
>>mention a lot of losses across your plate circuit. There have been a number 
>>segmented schemes which seem to work in a fashion. Seems to me that 
>>using a GDO is like setting your timing in your automobile engine by 
>>your eyes fast.
>C'mon now John....what do you think the commercial companies used back in
>days of old?  

Amen, Carl.  Dipmeters are still good for finding resonances, and they 
always will be.   A dipmeter showed me the falacy of using gapped choke 
sections on the same form.  
>A 1/2" diameter is ideal for 80-10M and maybe even 160M. The SB200-220
>choke is only 50uh but the first series resonance is around 45MHz. I have
>not tried extending that form factor to 100 + uh but it might bear some

As expected, the resonance moves down into the HF region, so you gotta be 
careful on which frequency you park it. 
>Also back in the 80's there was a HRM article mentioning the use of a
>ferrite rod inside a choke form...the reference was a 5KW commercial
>application with no series resonances 2-30MHz.  Later on B&W used that
>concept on their BBC-5K choke.

Two potential problems is that ferrite can saturate and ferrite is a 


R. L. Measures, 805-386-3734, AG6K   

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