>
>-----Original Message-----
>From: Bill Coleman <n2bc@stny.rr.com>
>To: AMPS <amps@contesting.com>
To: <amps@contesting.com>
>Date: 03 April 2002 02:04
>Subject: [Amps] WTD: 5CX1500A Datasheet
>
>
>>Thanks to all who aimed me at the Svetlana info - I should have mentioned
>>that I already had this in my first post. The Svetlana datasheet is rather
>>abbreviated.
>>
>>Anybody got an old Eimac datasheet, ...
? The Eimac data sheets do not have a constant current curve graph for
the rated screen potential of 750V. If you like, I can scan the 8-pages
and e-mail them to you in jpeg format. However, to me, the important
items are 75pF input; c. 3.1A of peak-emission at 750 screen V; 0.2pF
feedback; appros. 120v of bias; 250mA of ZSAC; and extraordinarily low
IMD at a screen-I of 60mA (AØ), or 30mA using 50wpm dits. Since the
plate-modulated rating is 3500V/7000V-peak, If I were designing a SSB
5cx1500 amp,. I would use an anode supply of c. 5500V no-load, 750 reg.
screen V, and a 50-ohm grid termination mounted close to the grid.
Neutralization may not prove to be necessary, but I would neutralize
because the 75pF grid will muck up the input match above 10MHz.
Driving P is c. 150W pep for a 50-ohm grid term. With a 200-ohm
grid-term., c. 38W. With a 200-ohm grid term., neutralization is
probably good engineering practice - unless one needs a VFO.
- To protect the screen from all Murphy-esque possibilities, I would
obtain the screen V from a string of zeners mounted on a perf-board.
(c.40), 20V, 5w zeners should work well. Zener bias needs to come from a
1500V or more source limited by a series R that limits current to c. 70mA
under normal conditions. [note -- in the real world, zener diss. ratings
should be divided by 1/3].
have fun
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
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