Everything takes time, and this IF channel rebuild is no exception. I thought building things in a separate chassis would make the job easier, but of course, it’s a tighter space to work in. And I spent, all in, about eight hours on this detour. But victory, and a small defeat, are mine. The oldContinue reading “Day 44 – A Qualified IF Success”
Well it’s been a week. I’ll keep the status report brief as the frustration has been pretty intense. The diode situation As mentioned last time, I feared that my recent (non-vintage) 1N34’s might be lowering the detector sensitivity. After finding the 1N67A’s at a CB shop, I did the swap, and there was a noticeableContinue reading “Day 38 – This is why they call it a Rabbit Hole…..”
Nominally, the JMD is complete for 80 meters. But I know better. I just do. The BFO output seems low, with no readily apparent fault. And there’s that mixer tube substitution. But to test my hypothesis, I fired up the signal generator and tried to get a signal from the antenna terminal to the speaker.Continue reading “Day 31 Into the Rabbit Hole”
Finally, a relatively straight forward couple of hours without any difficulty! You would hope a guy that has been a radio amatuer for 51 years might be able to build a triode oscillator without anything going wrong. But I’ve learned to take nothing for granted. All in, it took two hours to install the components,Continue reading “Day 29 The HF Oscillator”
The JMD mixer promised to be a king-sized PITA. First, I decided to use a 6JH8, affordably available, rather than the esoteric 7360 mixer. Swan did this swap in the 60’s to save some money, and the tube should be functionally identical. This meant wiring the 7360 socket with different pin assignments required for aContinue reading “Days 27 and 28 Mixered Up”
Having an oscillating BFO provided motivation for building the IF amp. Looking at the schematic, I thought this would be a two hour tour and I’d be ready to move on. But not quite. The JMD uses some IF coils that in the good old days were made from Miller coils installed in off theContinue reading “Day 26 IFfy Amp”
Well, 24 days into building a radio and I’m finally starting on something that works at radio frequency. It’s been about three weeks of lockdown and four weeks of isolation and I have to say, the project remains a great distraction from the news. True to the “build a stage and test it” philosophy, I’veContinue reading “Day 24 – BFO ho ho”
It’s hard to believe that it’s taken about 5 hours over the last few days to wire and test the 12AT7 audio amp but it’s sad and true. You can see the amp wiring at the bottom of this picture. I’ll admit, it looks a bit unusual, what with the size of components shrinking overContinue reading “DAY 20 – Can you Hear Me Now?”
The last couple of days have been spent trying to wire and test the JMD power supplies. It has not been without some unexpected difficulty. Yesterday my goals were to wire the on/off switch and transformer leads to appropriate tie points, test the voltages, and wire the filament string to light up the tubes. EverythingContinue reading “DAY 18 POWER PLAY”
The joy of metal working is directly proportional to the number of metal working tools you can access. At least that’s what I tell me wife. Not that I have much. A decent drill press, a good nibbling tool or two and some chassis punches are, for me, pretty much the minimum requirements for enjoying,Continue reading “DAYS 14 – 16 HEAVY METAL”
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