Based on the previous results, I decided to readjust the IDLING current for the final MOSFET Stage.
Using a digital VOM on its 10A scale, I interposed it in the positive line to the transceiver.??
When receiving with audio at 0%, the current was 0.52-0.53 Amperes
When transmitting SSB with drive at 1 and mike at 1, the current rose to approximately 0.99 Amperes (it changes with temperature as the devices heat up)
When the idle current adjustment was carefully adjusted, down to ZERO idling current, it read approximately 0.81 - 0.83 Amperes.
This indicates the idling current as RECEIVED was approximately 0.16 Amperes.? ?This was close to, but slightly lower than the idling current measurement that was on the very impressive TESTING SHEET that came with the radio, which indicated the idling current had been set to about 0.20 Amperes.
I decided to increase the idling current to approximately 0.36 Amperes (above the minimum and thus I carefully adjusted for a total current of 1.19-1.21 amperes.? ?I then reassembled the system....and in the process I damaged the DSI video cable.? ? Not having a suiitable spare, I was DELIGHTED to learn that I could see the screen of the unit by using an adapter to the HDMI port closest to the USB-C on the Raspberry Pi.? ?Hooray!? ?Able to continue testing.?
Now with an increased MOSFET idling current, I re-measured some of the bands as follows:
MHz? ? ? ? Fundamental? ? ? ? ? ? ?Any notable Spurs? ? ? ? ? ? ? ? ? ?2nd harmonic? ? ? ? ? ? ? ? ? ? ? ? ? ?3rd Harmonic
3.510? ? ?20W? ?73%? -20.8 dBm? ?approx -66dBm? ? ? ? ? ? ? ? 7 MHz -62dBm -43dBc? ? ? ? ? ? ? ?10.5? -72 dBm -51 dBc
7.010? ? ?20W? ?72%? ?-21.5 dBm? ? 10.5 MHz -55DBm? ? ? ? ?14MHz -60dBm? -38.5 dBc? ? ? ? ?21? -66 dBm? -44.5 dBc
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? (-44 dBc)
14.01? ? 20W? ? 78%? ? -21 dBm? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?28MHz? -47 dBm? -36dBc? ? ? ? ? 42MHz -52dBm? ?-31 dBc
CONCLUSIONS
1.? The 40 meter 2nd harmonic is 1 dB improved.
2.? ?The 20 meter 2nd harmonic is almost 12 dB improved -- HUGE improvement
3.? ?The 20 meter 3rd harmonic is a real problem.??
4.? ?All of my measurements are subject to question, this is NOT a professional measurement lab.? ?This is just the best that I can do with a very expensive (in my estimation) $1400 spectrum analyzer and reasonable layout of a radio as it might well be utilized in practice using a very popular power supply.? ?
I believe the 20 meter 3rd harmonic has been previously noted to be a problem.
OK.....so there is work still to be done on this radio!? ?I am concerned that the ARRL testing lab would conclude that it is not yet read for their testing and an article.? ?I think manufacturing is a MUCH more difficult task than prototype building (which in itself is a monumental task!).? ? So I think we should work together to make this so that Serila No. 141 (and most other radios) easily meets the requirements right out of the box.? ?Such an excellent design deserves to have this accomplished, yes?
Sincerely,
Gordon L. Gibby KX4Z
