Left Coast Political Scene

I found two old RPi3's in my junk box this morning and so an idea sprung from the junk stuff. With a bit of panache and a flare for the dramatic, I updated the software and included the vwspkg in the QUISK directory. Both took the VWS pkg software and after identifying the serial port as /dev/ttyACM0 and in a blink of an eye the MHST was receiving signals. JFF (Just For Fun) I installed a 50 Ohm resistor on what is normally the transmit output port of the steerable amp and put my scope probe across the resistor and this is what I saw. Damn -- it is working! That said it will not transmit with the RPI4 or RPi5. The RPi3 is configured as a 32-Bit machine and the 4/5 are a 64Bit machines. I have no explanation. True it is a crap looking signal with a lot of trash riding along but the 1st real sign of a signal output in transmit. Some big issues remain such as cleaning up the signal and the transmitted frequency is nowhere correct.  So, if you have an RPI3 -- you are good to go! MHST w...

  Today we start with an updated Block Diagram of the MHST (Minimalist Homebrew SDR Transceiver). Let us start by tracing the Receive and Transmit Paths. Essentially the Received signal starts at the Analog front end passing through the TR Relay into the Main Board. The received signal is first amplified by the Steerable Amp and then passes this signal stream on to the Band Pass Filter.    From here a simple FT-37-43 transformer splits the received RF signal into two RF signal paths passing one each to the RF input side of the two ADE-1's. There in each ADE-1 a Quadrature LO signal introduced from the Pi Pico converts the RF signals into two audio streams (In Phase and Quadrature -- I & Q).   The next step is the Sound Card which processes the two audio streams into the RPI5 for signal processing and displaying the signals on the HDMI Screen and sending recovered audio to a Headphone/Mic Sound card dongle.  The Optimal Shop Sound Card has both a stereo ...

More progress on the MHST rig and thus some more sharing. I note that when there is nothing but boring words, the interest level drops. This often happens on the weekend posts. So, for this last day of March 2025, hopefully more interesting stuff. The MHST project has two main elements and these are of course the hardware and the software. The more visible of course is the hardware and even then, not much of that. The not so much seen of course is the software. Both are needed to be working for the total rig to work. I posted a video about some of the progress and problems if only to show it was alive. One comment -- hey you have the presence of the opposite sideband image. That was true as the video was done without any adjustments. Contained internally within the QUISK software is a means to compensate for not so perfect hardware where component tolerances do not create the perfect 90-degree phase shift. In fact, you have the capability to make these adjustments over the whole band o...

I am happy to report that I now have the Pi Pico able to work with the RPi5 SBC. The issue was that the package to recognize the Pi Pico has to be manually loaded into the QUISK directory. Once installed what should normally happen is that when QUISK is executed that radio should show up on the menu. It didn't on the RPi5 SBC. It was a mystery as using essentially the same process the radio did show up on the Windows 10 machine.  Then, I decided to closely read the instructions where I spotted something you needed to do differently for the Linux install. Dah RTFM! Suddenly the MHST rig is in the list. I still have a few warts to polish off but a huge step in reducing the size of the rig with the bonus of the features in the Linux form factor versus the Windows 10. One really important Linux feature is the Pulse Audio Control Panel that is loaded in a terminal like this. sudo apt-get install pavucontrol This control panel gives you a whole series of adjustments and selections with r...

A productive day yesterday on two fronts. I visited the XYL at the cemetery to bring some of her favorite flowers and was happy to see that the headstone was installed. I had been told it might take six months. Now no longer an unmarked grave. The second front was the MHST is back on track. As I had suspected it involved the software. This requires a bit of explanation that deals with the two different approaches using the QUISK software. (Windows/Linux) But let us start with some fundamentals of the I/Q implementation which is basically sound cards -- TWO of them. One sound card, typically external, involves the processing of the I/Q data stream to/from the computer. The second sound card handles the Audio output and Microphone input. This often is an external sound card built into a mic/headset dongle. In a Linux implementation using a RPi3, RPi4 or RPi5 there is an issue with using any internal sound cards on the SBC. In the earlier Pi Models, there is an on-board Headphone jack but...

For some strange reason my mind works while I sleep and often, I will awake with an answer to a confounding problem from the day before. That didn't happen last night! Instead, I did think of a new mantra to describe the situation. Things simply do not aright themselves through spontaneous correction. Yesterday was both a Good Day and Bad Day at the bench with the MHST project. First the Good News. I was able to get a HIGH on GP2 when you hit the PTT button on the QUISK panel. It all boiled down to adding a #define statement in the Arduino IDE that cites the Pin title and GPIO Pin Number.  That worked but for as fast as the Pi Pico is (133 MHz) there is a noticeable delay (with no internal delay statements in the code) from button engagement until there is power on the pin and the same is true once the button is released. Thus, not like unkeying the Microphone and you are in receive. More opportunities for going down the rabbit hole. But then the two Bad News Stories. I noticed a w...