I haven’t posted anything in quite a while. I’ve been very busy and haven’t had much free time to tinker with things, but I have been working on a few projects. I just haven’t finished any of them. Since my last post, I’ve gotten a new 3d printer, a cnc machine, a bunch of stuff to restore and/or fix, a few new radios to mess around with, some kits to build, etc.
Well, since my last post, my house took a direct hit by lightning, I spent some time in the hospital, and my job built a new headquarters and we moved in, so I haven’t had much time to work on anything in my spare time, but I did recap and mod an old Heathkit Laboratory Generator, model IG-42. This is the inside before I did anything. You can see all of the old caps that needed replacing.
I’ve been following along with ZL2CTM’s latest Teensy SDR transceiver build and I’ve been trying to emulate his design even down to his construction style with the strip board. So far, I’ve got the radio receiving well enough. After troubleshooting a bad grinding and squealing noise for a week, I found a bad audio transformer. After replacing that, the rig came to life. I was able to generate the quadrature oscillators with the SI5351 as detailed in this post and I’m amplifying the audio with the teensy itself, rather than an external audio amp.
Over the weekend, I ripped apart an old DVD burner and harvested the laser diode. I needed something to drive it, and there is a simple trick to use an LM317 adjustable voltage regulator as a constant current source. The datasheet mentions this: The device OUTPUT pin will source current necessary to make OUTPUT pin 1.25 V greater than ADJUST terminal to provide output regulation. I used this functionality to build a constant current driver.
Between April 11th and the 14th, the ISS was broadcasting SSTV images related to the Interkosmos program on 145.800 MHz. I was able to grab two images while I was in my truck with a terrible setup. I had a baofeng radio connected to a magmount antenna and was running Robot36 on an android phone. I was surprised that I was able to pick up anything with that mess, but the two images below are what I was able to decode.
I’ve been following ZL2CTM’s video series on building a phasing sdr rig with a teensy and an si5351. Charlie used a SN74HC74 and an RF splitter to generate the quadrature oscillator signals, but I wanted to see if I could get the si5351 to generate the quadrature signals using two of its outputs. The Etherkit SI5351 library has an example that shows how to set the phase and I took that example along with Charlie’s teensy sketch and put together a quick example of generating quadrature signals from CLK0 and CLK1 of an SI5351.