KX3 Behavior with Brick Amplifier

[Richard Lawn]

I took an old Palomar solid state "broadband" amp and added a band pass
filter to the output to clean things up. I then tried it with my KX3 and to
my surprise the SWR was showing high at the KX3. The filter alone attached
to a dummy load shows a near perfect 52 ohms so the problem isn't on that
end of the chain.  If I use an inexpensive littte 5 watt 40 m QRP CW rig to
drive the amp everything seems perfect with nearly 100 watts out of the
amp.Should I assume that my idea to recycle an old CB amp was just a bad
idea and cut my losses by throwing it away?  Or am I missing something?

Rick, W2JAZ
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[Jim Brown-10]

On Thu,3/9/2017 1:11 PM, Richard Lawn wrote:
> Or am I missing something?

I'm guessing that that amp is a POS. You can filter harmonics, but you
can't filter IMD. I'd throw it in the trash. The SWR issue is likely
because the input circuit is tuned for 11M and doesn't pass whatever
frequency you're trying to drive it with.

73, Jim K9YC

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[Elecraft mailing list]

Or , you can turn the amp on with a keying line and sweep the input with a analyzer to see where it is matched.  CB amps are notorious for having very narrow input match networks, like Jim said, but the transformers are most likely broad band.  Worth tinkering with if you want to see whats going on..
Mel, K6KBE

      From: Jim Brown <[hidden email]>
 To: [hidden email]
 Sent: Thursday, March 9, 2017 1:49 PM
 Subject: Re: [Elecraft] KX3 Behavior with Brick Amplifier
   
On Thu,3/9/2017 1:11 PM, Richard Lawn wrote:
> Or am I missing something?

I'm guessing that that amp is a POS. You can filter harmonics, but you
can't filter IMD. I'd throw it in the trash. The SWR issue is likely
because the input circuit is tuned for 11M and doesn't pass whatever
frequency you're trying to drive it with.

73, Jim K9YC

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