>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 <measures@vc.net> writes:
>>.........
>>>I would also try and obtain schematics from Command, Emtron and any
>>other
>>>company that is using the Svetlana 4CX1600B. There should be
>>excellent
>>>information on no hassle input circuits, protection, etc.
>>>
>>- No hassle HF input circuits dismiss the importance of
>>neutralization.
>
>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
>viewpoint.
- 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 www.vcnet.com/measures}
>>
>>cheers
>>Rich...
cheers
Rich...
R. L. Measures, 805-386-3734, AG6K
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|