A couple of weeks ago, we were down visiting Bob, K9QLL and he gave David a crystal radio set. It was nearly complete — I had to provide a couple of pieces of hook-up wire. David connected it up to a 7 foot wire for an antenna and used my truck for a ground but didn’t hear anything. I thought that was weird, so I brought it into my shack/workshop, where I could bring $75,000 worth of test equipment to bear. During troubleshooting, we found that the 1N34 diode (that is the ‘heart’ of the 4 component radio) was open. Rummaging around in my parts bins, I found an old Motorola 48-82139G01 diode that had been resting for, oh, a couple of decades. This was not a 1N34 but was a germanium type transistor, a requirement for the circuit to work. Past time for it to go to work — replaced the bad with the good.
Since we were in the shack, I had David hook the ground wire to my metal desk and the antenna to my 160 meter vertical antenna (hey, if you’ve got it, use it!). The radio set sprang to life and WGN at 720 KHz started blasting in — I could hear it without the headphone to my ear.
I am imagining that David is going to become quite a WGN listener from now on. Hmm, maybe I can improve the selectivity so that he can pick up TWO stations. . . .
BTW, when I was a kid, I had the ‘rocket’ style crystal set (1950′s), that was held in one hand and tuned with the other by moving the stick in and out. Picked up WNIL and some South Bend stations. Got me interested in radio.
- Jakarta Mark, K9AM
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My crystal set was given to me by my granddad (original W6LSN) when he visited us in Hawaii. Previously, we’d visited him in SoCal and I was enamored with seeing his voice on the ‘scope in the shack.
The radio was built on a small board with a coil wound on a an over-sized toilet paper tube. An air variable cap rounded it out with of course the obligatory Germanium diode. I could here the local station in HI, and at night could hear stateside stations from LA.
ground was to the water pipe and antenna was bell wire under the eaves. Everything was held together by Fahnestock clips. Fell asleep many a night listening to that…