HFU HF Underground
Technical Topics => The RF Workbench => Topic started by: ThaDood on January 12, 2024, 2000 UTC
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For decades, I've used cheap, trashed, second-hand, car radios / stereos, for AM and especially FM, DX'ing. Apparently, I'm not the only one doing that. https://www.antiqueradios.com/forums/viewtopic.php?f=12&t=433522 Boomer and I were kicking that idea around and he found that post out there. Well, when you can get a second-hand AC Delco car stereo, for free, with great sensitivity, and especially selectivity, spec's, and be a kick-ass DX'er for using it, why not?!? Even, back in high school, one dude home brewed his own boombox from a car stereo, a pair of 6 X 9 speakers, a lead-acid battery, and a wooden case. And, it didn't cost him over $400.00 to do it, like what a Panasonic 'RX-5000 series' box cost. Back then, he was seen as weird for doing it. Today, I can look back and say that was pretty forward think there.
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Back in the 1970s I had salvaged an AM / Shortwave tube type car stereo from a relic at the local dump. I wish I would have kept it. It would have been interesting to play with. A lot of the European automobiles had broadcast shortwave bands in their car stereos. Sony also manufactured one.
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I did that back in the 1980s, worked great.
Locally, the FM band here is packed full. Just a handful (very small handful) of open channels left.
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When it comes to older car radios, note you might need to add some attenuation if planning to use more than a short wire or whip for an AM antenna. AFAIK, most (nearly all?) of the older AM car radio circuits are single-stage superhets. You likely do not want to lose selectivity due to overload.
If the radio is old enough, also plan on potentially having to adjust the radio's varicap used for matching the car's antenna (whip+body | Kirchhoff's current law) and feedline to better optimize AM performance, particularly with small simple antennas. Conversely, more typical MW/HF antennas probably have enough gain to overcome losses due to mismatch.
BTW, many car radios these days are SDRs. Goes the other way as well. For example, the popular Airspy HF+ SDR uses the STA709 tuner originally designed for automotive receivers.
https://www.st.com/en/automotive-infotainment-and-telematics/sta709.html
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For decades, I've used cheap, trashed, second-hand, car radios / stereos, for AM and especially FM, DX'ing.
I have fond memories of listening to the AM radio in my father's 1966 Plymouth Valiant and hearing amazing DX. Had to be careful not to run down the battery. :)
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I have here somewhere a 1980s radio from a Datsun (Nissan) car. It was superb on AM. I would love to mount it on a panel with speakers but I can't find the radio. I also have a radio from an Opel car which is good. It even gives a read out of signal strength which was useful when I was transmitting on MW. I might mount that instead.