Done!... just finished building and calibrating.. bottom line? have already made several QSO's, getting 5w out with 12.5vdc supply.
I powered it up yesterday and tested it right in the middle of a contest!. Great time to check out the receiver with all the big signals on the band.
Very impressive opposite sideband rejection!. Honestly, I wasn't expecting performance like this but was very pleasantly surprised.
A few observations....
If hadn't watched this video, I would have had a much harder time performing the alignment procedure and tweaking the LPF for maximum output.
My worries about correctly winding T1 were for naught. Got the peak just where it should be. As Hans mentions in the video, the 20 meter version rarely needs changes. This verbal explanation in the alignment section of the manual at first had me like a deer in the headlights....?
"It is very important to understand the number at the top right of the LCD, here shown as 09. This is
an amplitude scaling factor, expressed as a power of 2. In this example, the actual amplitude is
divided by a factor of 512 (2 to the power of 9) then displayed on the screen. In this photograph,
27 little vertical bars are shown, which means the actual measured amplitude value is 13,824."
.... and again, after watching the video, the lightbulb went on and I figured out that the numbers in the upper right corner
represented different ranges of amplitude... oh yea, I get it... (grin)
I ended up removing 3 turns on L3 and moving the turns around to get max output. Just squeezing turns together a little on L1 and L2 and there? it was, 5 watts out. Didn't have to touch L4.
I guess the only real "Issue" i had was fitting the front panel PCB to the optional enclosure. The "black 20mm M3 screws" that hold the LCD module to the PCB are too big for the holes on the LCD module. they will not just slide through. You have to actually force thread them through. I could have enlarged the holes in the LCD module slightly but I was afraid of damaging the multilayer LCD PCB. One more point... It would be WAY easier if you used non-threaded spacers between the PCB and LCD module and only used threaded nuts on the back of the PCB. I was having such a hard time getting everything tied down because of those threaded spacers, I ended up using some nylon, hollow, non-threaded standoffs that I happen to have and that did the trick.
Not a complaint really, but I was disappointed in the AGC module.... Setup as suggested, setting the pot so it barely cuts down the background noise, it still let somewhat bigger signals come blasting through. Since this is an audio AGC, I was thinking there must be a better audio limiter/compressor circuit that can be implemented here. There isn't enough gain reduction when bigger signals hit.
Let me say, in the end, I absolutely love this radio!. in fact I'm ready to order the 40m and 30m versions.
An incredible design, Hans is a genius. If you take your time with the build, pay attention to details, you will end up with a box of fun!
Glenn W2BX
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