[Elecraft] OT: modifying your amp for lower drive requirement

[Vic K2VCO]

Well... keep in mind that an input attenuator also reduces the SWR seen by the exciter. 
Even a relatively small 3 dB pad means that the SWR can't go above 3:1 even if the input 
impedance of the amplifier was zero or infinite!

On 12/20/2010 2:09 PM, DOUGLAS ZWIEBEL wrote:
> Almost 30 years ago now, before I was 99.9999% a QRPer, I had an Alpha
> 76CA (3 tubes).  It had a giant swamping pad on the input (I still
> have it - the swamping pad, that is).  Just take it out and like
> magic, you could drive the amp with QRP.  My intention was never to
> exceed legal limit, just to be able to use the amp when driven with a
> QRP rig. I don't remember how much out I could get with QRP in, but it
> was nowhere near 1500 watts.
>
> I have no clue what they have on the inside of the KPA500, but if
> there is a swamping pad, you can probably take it out.  What is
> Elecraft's motto?  Hands-on radio?  :-)
>
> When I used to use a Ten Tec Titan Amp, it required 36 watts of drive
> for 1500 watts out on 20m.  That was probably 25 years ago.
>
> Finally, if you want to fly under the radar, there are certain high
> quality amplifier manufacturers overseas (closer to W6 than W2...hint
> hint) who will custom make you an amp for low power drive.  Check the
> FT817 Yahoo group archives.
>
> de Doug KR2Q
> had my fill of QRO ages ago
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-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/