I wanted to know how I would have done building a first receiver from scratch. So, fifty years later, I found out.
John’s recent column about his first receiver – a Knight-Kit R55A – ended with an observation that he might have been better off not building a first receiver. Last year, I built a single conversion radio to use with my old 1625 transmitter in the Novice Rig Round-Up.
The object of my desire was the Junior Miser’s Dream (JMD, shown above), from a 1960’s ARRL Handbook. The name suggested to me a beginner’s receiver – subsequent events proved otherwise. Other novices built regens, or Handbook-favorite 80 and 40 meter band-imaging superhets. Boring.
The JMD seduced me half a century ago. Cool dial, high IF 2 crystal filter, a 7360 mixer, AGC and a two diode product detector! It even had a RF (not IF) Q-multiplier! Years ahead of its time.
And it probably was. Despite decades of researching emerging technologies in my day job, I decided to build it, without looking for evidence of a single working example built by a mere mortal. And definitely not by a novice vacuum tube receiver builder.
It was a rocky road. Being a product of the ARRL lab whiz kids, the radio used special coils, an exotic tube, a hard to find AGC transformer and had a fairly critical layout. The Lab even had the sense to warn you that the inductors they selected were vital.
Building a First Receiver – Finding Parts
Yeah, sure. In the true spirit of amateur radio I’ll build with what I find. T.O.M. would be proud. I had a garage filled with 50 years of hamfest flotsam and jetsam. And I’d been generously provided an old HR-10B chassis with a good power transformer.
The chassis was stripped, and the holes naively filled with the JMD design. I couldn’t find a 7360, so I borrowed a 6U8 mixer circuit from the same Handbook chapter. The IF crystals were unobtanium, but I found on old Heathkit filter near the required IF. And I wound some coils on whatever cores I could find. If those coils didn’t work, I’d try some plug-in coils from the Handbook’s DCS-500. And I’d keep shopping eBay, or redesign the front end. I’d be done in a few weeks.
Or, maybe not. More on my actual build in the next article and on my blog, Scotty’s Skunkworks. Check out the original JMD article on page 126 of the 1967 ARRL Handbook.