Power output for the QCX mini 20m version #20m #power


Christian Gosch
 

Hi all,
I got to the point of measuring the output power of my newly built QCX mini. It started with a fairly low 1W or so,
and following Hans' youtube video on tuning up the QCX, I managed to get it to something that looks like just under 4W with 13.2V,
by spreading out the windings on L3 as described in the video, and squeezing L2 and L1 a little.
Is that value what I should expect for the 20m version? Or might I be able to get a little more by removing a turn from L3 like mentioned in the youtube video also?
I should add that I use a Daiwa analog power meter set to 0-15W range, and I am not entirely certain how accurate it is. I believe they say 10% error, which would put it somewhere in the 3.6-4.4 Watt range.

Christian


Russ AB6MU
 

On Mon, May 17, 2021 at 09:29 AM, Christian Gosch wrote:
Are you using the Daiwa analog power meter with a dummy load?


Christian Gosch
 

Yes, I am using the QRP-Labs 20W dummy load (got that along with the QCX mini kit).


Christian Gosch
 

The reflected power needle is staying at 0 while I am keying up.


Russ AB6MU
 

OK, good. You will probably be able to get a little more power by removing a turn as Hans demonstrated in the video he posted.

I ended up removing one turn from L1, L2, and L3 on the 20m QCX mini that I build.


Christian Gosch
 

Thanks Russ!


Skip Davis
 

Christian,
Start by removing one turn only from L3 and then expand or compress the turns on L1&2. I just unwind one turn and tack solder the wire back to check BEFORE CUTTING THE WIRE to length.
Just remember that spreading the turns reduces the inductance and compressing them increase it. So if after removing one turn from L3 and spreading them out still increases output them unwind one more turn to see your results. Getting about 4 watts out is good for the 20m QCX when you’re are using about 12vdc for power, that is what I use as a start voltage which matches my portable battery pack ( about 12.8 vdc charged after resting).

73, Skip NC9O


ke9uw
 

I did the same and got 4.5 watts out starting out at 3. If I get 4 or more, I quit.


ke9uw
 

BTW, I use the QRPoMeter. Pretty handy digital meter/dummy load. Fun to build too.


Christian Gosch
 

Oh thanks, I hadn't heard of that one.


Christian Gosch
 

Thanks all and thanks QRP-Labs for the excellent Youtube videos. Removing one turn from L3 and compressing L2 further resulted in about 5W out with 13.1V (happens to be my battery voltage), and 6W with 14V, which happens to be the output of my 13.8V power supply (according to an inline meter).