[Amps] 4CX1500 QSK

[R.Measures]

On Nov 2, 2004, at 4:09 AM, Mark Hill wrote:

> Rich,
> Karl-Arne,
>
> Many thanks for the suggestions.  Having looked at the circuits for 
> the amplifier section, I think leaving the screen Voltage present at 
> all times and switching the grid bias would be easiest.  Prompted by 
> your circuit idea Rich, I have dug out a suitable power FET and OPTO 
> that should handle switching duties.
>
> Rich, it seems as though this particular TX /amplifier has been 
> optimised for very low IMD at the 1 kW level - probably because there 
> were lots of them in close proximity to one another.  The manual 
> quotes IPs as better than -36 dB on either of two tones (CCIR 326-2).

Mark -------- Which is better than virtually all Ham transceivers 
presently available.

> The operating parameters seem to be taken more or less straight from 
> the Eimac data sheet for the valve.  I noted you point about the valve 
> being capable of producing more Watts.  I may try just a few more 
> Volts on the screen out of curiosity,

More power is good when conditions aren't.  On SSB, with good 
conditions, if one does not need as much power, one can simply turn 
down the microphone gain control.

> but the low IMD probably betters my triode units and will be good for 
> local rag chews and digital modes.
>
A 3-500Z in g-g does typically better than -40db on IMD -- thanks to 
the inherent RF-NFB of g-g operation.  .

cheerz

> Karl-Arne, the Collins sounds like an interesting unit.  I hope I 
> don't come across one at a bargain price - it would be terrible to 
> have to choose between a lovely wife and a 'tube with handles'!
>
> Regards.
>
> Mark.
>
>
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Richard L. Measures, AG6K, 805.386.3734.  www.somis.org