Heathkit HR-10B as a SDR front-end?

A fellow ham has an old Heathkit HR-10B receiver and based on some recent experiments I thought it would be interesting to see if using SDR software with an old radio like this, it would make it more useful.



Since the radio had sat in a garage for many years the first step was to clean it up a bit. The chassis was covered with about an inch of dust and dirt. I removed all the tubes and inspected and cleaned the sockets and I was surprised to find the radio was now working! There is a bit of hum in the audio so the electrolytic capacitors are in need of replacement.




Since I wanted to connect this to a computer I will need an audio interface to be safe since there are high voltages in the radio up to about 300 volts. This gave me a reason to finish my audio interface that I started back in October HERE.



This is the completed audio interface cabled to the radio. I just used the RX AF to TO PC side of the interface to connect it to SDR-RADIO.COM v1.5 software.



I was surprised with this setup and with a lot of fiddling I was able to view about 6 khz of spectrum and tune CW and SSB signals just fine. The radio does drift but after an hour or so it is not too bad and you can listen to a SSB QSOs, CW, etc. and only need to adjust it every 5-10 minutes. I even decoded a PSK-31 signal. It will only hold on frequency for 10-30 seconds with PSK-31 but it can be done.