In a message dated 30/12/2004 07:57:33 GMT Standard Time,
avilaseca@bluewin.ch writes:
> I've got some papers from an IEE Conference on HF back in 63, where they
> were described. There'a also a paper from STC about a 60kW tx:
Could you please make some info available?
I can photocopy and mail next week - I could try getting the XYL to use her
scanner if she has time before she goes off on her next business trip.
Personally, I'd just use the distributed amplifer as a source of parts. Use
4 4CX250B's for 1kW out, and you'll get a relatively clean 1kW. 4CX250s
aren't the most linear of tubes - bear in mind the basic design is 1946, and
they
weren't looking for linearity much then - but put some negative feedback on
it and you'll improve the linearity - I assume you're driving from the usual
transceiver power level, so you've plenty of power available in passive grid.
Use a shunt regulated screen supply, too. Easiest way to do NFB is something
like a 10ohm 2 watt metal film resistor in the common cathode lead to the 4
tubes, shunted by an RFC of around 10 or 20 microhenries, wound on a bit of
ferrite - you want an impedance of greater than 100 ohms over the operating
range. You can often liberate suitable chokes from old switching power
supplies.
73
Peter G3RZP
10 4CX250B's for a kW is still a lot of electricity for the blower, heaters
etc. And nobody describes distributed amplifiers as power efficient for narrow
band work.
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