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[AMPS] 4CX1000A advice??

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Subject: [AMPS] 4CX1000A advice??
From: (Rich Measures)
Date: Sat, 14 Mar 98 05:44:02 -0800
>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.  

>On Fri, 13 Mar 98 08:40:20 -0800 Rich Measures <> writes:
>>>I would also try and obtain schematics from Command, Emtron and any 
>>>company that is using the Svetlana 4CX1600B. There should be 
>>>information on no hassle input circuits, protection, etc.  
>>-  No hassle HF input circuits dismiss the importance of 
>So you already are condemning the Emtron, QRO and even the Alpha amp or
>anyone into tetrodes? You are beginning to sound like someone else.....

-  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 termination 
R to improve the 12m and 10m input SWR.  Doing so is an invitation to vhf 
oscillation.  If Emtron, QRO, and Alpha do not use such a circuit,  Good. 
 .   However, one does not know until one sees the circuit. 
-   If a manufacturer of a Class AB1 amplifier is using a cheapo grid 
input circuit, buyers need to know about it, Carl.         .  

>Me......I want to know what REAL companies are using, not just your

-  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.  
The bottom-line is that "no hassle" is usually more hassle than doing it 
right in the first place.   

>The Svetlana 4CX1600B (or 2 ) looks increasingly interesting.
Agreed.  However, for c. 1500w, you only need one.  For the price of 2, 
we are getting close to the price of a more-interesting, larger tetrode 
that has an instant-on cathode plus a much tougher 75w grid.  
>> With a grid termination R of 12.5 ohms, no problem  With a grid 
>>termination R of 50 ohms, maybe no problem.  With a grid termination R 
>>of 200 ohms, good luck.  With 450 ohms, enjoy the ride.  
>>-    Eimac says that neutralization can be important in grid driven 
>>linear service, and, as an added bonus, neutralization results in a 
>>virtually perfect input swr.   The neutralization circuit  is simpler 
>>than most folks seem to expect.  {Figure 5 at}


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

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