The RPi3 has served me well as a solution tool. So, today I added a commercial 10dB gain block to the main SDR board and could see that the output signal using the RPi3 was being way overdriven -- read extensive flat topping.
One of the files that Jim Ahlstrom does not mention in the setup of QUISK is the control panel for the Pulse Audio. In a Linux terminal window simply type in:
sudo apt-get install pavucontrol
This is an app that has about six menus where you can set the various levels for the two sound cards. It is a critical tool. Now the Optimal Shop USB Sound Card takes inputs via the Line Input as well as produce outputs via the Speaker ports.
So, in noting the Speaker output level for the Optimal Shop sound card I "cranked" it down and the scope pattern suddenly cleaned up!
See CM106 Sound Device Analog Stereo and the Port Speakers.
Line In controls the Received level and the Speaker Port controls the level for the I and Q sound card for the transmitted signal
It was like air: Not enough and you die and too much and you go nutty. The huge light bulb went on -- where is that setting on the RPi5. Yep, it was on silence. Adjusting that speaker control produced an output. With 6 volts PTP output from the commercial amp -- terrible distortion and overdrive. With 2 volts PTP out of the amp -- a clean signal (cleaner).
My goof I just did not think about the speaker output level as the critical piece for transmit. The 2nd speaker output level on that same page is for the headset/microphone dongle.
This is a huge step forward and now we will work on the Analog Front End and the Transmit Power stages.
Them that know can make it go.
We had 77F weather yesterday and indeed a great time of year. Seems like there were a lot of demonstrations yesterday regarding old what's his name. So, did you really have any expectations that this time would be different? How is your 401K doing?
73's
Pete N6QW