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[AMPS] 4CX1000A advice??

To: <>
Subject: [AMPS] 4CX1000A advice??
From: (km1h @
Date: Sat, 14 Mar 1998 11:54:58 EST
On Sat, 14 Mar 98 05:44:02 -0800 Rich Measures <> writes:
>>Rich, first of all how about adding a few spaces between messages and
>>your replies....some of us older folks might appreciate it.
>OK, Carl.  I keep forgetting that there are e-mail apps. that don't 
>automatically change the colour of  the quoted lines, like Claris 
>E-Mailer does.  Unfortunately, they only make a Mac version.  

Add another line or 2 of seperation Rich...please. 

>-  I am opposed to "no hassle" untuned inputs for grid-driven tetrode 
>amplifiers.   One of the "no hassle" untuned input circuits floating 
>about recommends putting an inductor in series with the grid 
>R to improve the 12m and 10m input SWR.  Doing so is an invitation to 


  If Emtron, QRO, and Alpha do not use such a circuit,  
> .   However, one does not know until one sees the circuit. 

I do not know what they or Alpha use.

>-   If a manufacturer of a Class AB1 amplifier is using a cheapo grid 
>input circuit, buyers need to know about it, Carl.         .  


>-  I built a "tetrode with handles" amplifier.  I asked the recognized 
>amplifier "experts" about the input circuit.  I took their advice and 
>used a "no hassle" grid input circuit without neutralization.   The 
>amplifier was not stable.  This experience changed my viewpoint, Carl.
>-  I read "Care and Feeding...".   I removed the "ho hassle" input 
>circuit, incorporated Eimac's advice, and the amplifier became stable. 

Each tube has it's own requirements and peculiarities. I have only worked
with the 4CX1000A/1500B in traditional tuned grid driven military and
commercial amps. I have kicked a few 30S1's but didn't get into RF

Actually, at the 1500W level and 100W drivers I fail to see any reason
for a tetrode if one must use a tuned input and neutralization. An
8877/YU-158 makes more sense considering the availability to the home
For handles, I would still prefer GG with a YC-156.   A typical rig will
drive it to over 8KW and at less Ep than the 4CX5000A.  Available as
medical pulls for reasonable money, no socket required, no fussy extra
power supplies and superb IMD. 


73  Carl  KM1H

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