Re: QCX-20 ... low output power (~1.5 W) #qcx #20m


Bill Cromwell
 

Hi Rob,

So you were measuring across a 50 ohm dummy load. Aome of the variation *could* be in the dummy load or whatever bits you are using to connect it. As you hold the key down things begin to warm up. Even if they don;t get overheated there are still physical changes. That could account for the bit of wobble you are seeing.

The drop to 300 mW being intermitt is no doubt a poor connection somewhere. You know what to do about that:) I have a radio here with a lot of miles on it that I got cheap as 'not working right'. It had a similar problem to yours but on receive. I discovered a fractured winding on an inductor and had to rewind it. Look for things like that. Use a plastic prod to poke parts while transmitting into the dummy load (for brief periods). That will help you find the 'flaky' part.

73,

Bill KU8H

On 5/31/20 10:34 AM, Rob French (KC4UPR) wrote:
Bill, I had a dummy load connected abs wad using the built in RF power meter to measure across the dummy load, at the center pin solder joint (on the back of the PCB).
That all makes sense about harmonics.  Maybe more salient is that the transistor output seems rock steady whereas the LPF output appears to wander a little (when it's not dropping to 300 mW).
Rob  KC4UPR
--
bark less - wag more

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