Scotty,
the idea is good, but as you can see in the software version of the program, there is no one who would implement all this. For different reasons: those who could do it don't have free time for hobby solutions, and those who have free time are just trying because they've never done it before.
To all,
Since I don't like half solutions either, I started implementing what I can.?
Since I've had the device since last April, but I didn't have time to use it, I started with just a few modifications.
When the shipment arrived, I first checked the screws. Here, the FET amplification was the problem.
I modified this. Then I noticed that there is no output power for the dummy load. I looked for the reason and in the swr circuit around the diodes, one of them led both ways. I replaced both diodes because I had the opportunity to select ones with almost the same opening voltage from a previous purchase. I made this setting (according to the instructions from early May).
Unfortunately, the power display is not accurate (it shows a higher value than the external swr meter placed on the output)
but I noticed that I don't have a good idea how to modify it, so I didn't dive into the solution.
However, I didn't like the Bias setting at all, so I modified it so that the temperature of the FETs is monitored by the 6 Si diodes connected in series and thus affects the Bias voltage (the idea comes from F5NPV). I have published several pictures, this and my cooling solutions can be seen in the photo. I did the cooling because ft8 and especially the sstv mode has a long transmission time. I don't like to change parts often, so I pay attention to what needs to be cooled better.
Unfortunately, initially I only used the device on battery power. When I tried to set the transmission or the Bias (I don't remember which one anymore), one of the final stage with FET was shorted. From then on, I only use it from a power supply with a current limiter, and it (knock-knock) still works with my first installation. However, there were more than 4200 qso's (in ft8, ft4, sstv, js8call modes).
That's why I recommend this power supply to everyone.
One more thing: I definitely wanted to exclude the use of an antenna tuner, so I built an antenna that works well on several bands. This is a vertically fed loop antenna installed at an angle. I had a similar antenna in previous years, which I tuned to several bands with the Drake L4-B output tuner. At the moment, I can only use this one antenna and it does not need a tuner. It is rated at 7MHz, which can work well at 14 and 21 MHz.?
We are close to QRP performance, so a good antenna is very important, I think. This is proven by the fact that 3D2CCC also answered in ft8 mode, and several dx stations also succeeded. Of course, for that you had to be in the right place at the right time.
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Gyula HA3HZ
HA3HZ