Due to higher loss of driving level for the internal PA of the AMSAT-Transverter PA, I decided to go with the 20W PowerAmp by SG-Labs.After some measurements and combining information from AMSAT I decided to buy the newly available Version 3 of SG-Labs PA.After 2,5 weeks I received the PA from SG Labs without any issue.Communication with Hristiyan, LZ5HP was quick and easy.I ordered the PA with 3 three additional feedthrough capacitors to have the possibility to measure via directional couplers- Input Power- Forward Power- Reflected Poweras relative DC voltages up to 5V.These 3 channels, will be measured later with my homebrew microcontroller project.PTT issueAfter mechanical work for the capacitors I connected the PA to my AMSAT-Transverter.From professional power supply, I saw a steady current of 0,5A, which was the Quiesant Current of PA.Ok, PTT doesn´t work as expected…The idle voltage level of AMSAT transverter is 3.3V and PTT active 0V.Adding a series diode e.g. 1N4148 in direction PA solved the problem!In addition the PA has a RF Vox and I reduced the decay time to minimum level (internal VOX HOLD TIME potentiometer).
NB - PA (20W - class AB, SG-LAB V3 PA)
Measurement Output Power vs. Supply Voltage (interesting)
I was really impressed about the functional and controllable power range (even with attenuation).The first picture shows the PA output power from driving level of AMSAT-DL QO-100 Transverter using 2% Driving Power of ICOM IC-9700.From investigation of AMSAT UpConverter, overdrive of TX mixer starts with 4% of Driving Power from IC-9700, see 2nd picture below.Communication via Satellite was possible down to 25dBm of transmit power, this is equal 0,3W power level.
SG-Labs 20W PA (pictures)
Up:Internal view of PA- Driver is NXP MMG30271B- PA is AMPLEON BLP9G0722-20Left:Closed setup, ready for operation.Used some thermal grease from Thermal Grizzly Kryonaut.Heatsink in my case is 160x100x40 and is oversized, but was available from Flex1500 (something around 0.7K/W).After 1h of SSB operation maybe up to normal temperature of 37°C.
Here you can see my live measurement setup. Using directional coupler with 40dB attenuation + 20dB additional attenuation and using ADALM Pluto device for carrier measurement.