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.