Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
this circuit radiates as well, albeit at very low power, but if your antenna is cut right, and conditions are right, you have a slim chance of contacting a ship by using the device as a transmitter as well, to get you off the desert island.....
yes, since the circuit is an oscillator at the received frequency. one of the reasons this circuit is no longer commercially produced (and hasn't been, except in the form of hobbyist circuits in many years), is that radiation from the oscillator is coupled back into the antenna. back in the 30's, Great Britain instituted a "receiver tax", and a big splash was made in their media about direction finder vans that could detect "unlicensed receivers", because at the time most receivers were of this. or similar type. the truth was, it was just media hype (the "searches and arrests" made on film were completely bogus), but the fact remains that regen or super-regen receivers do radiate.... even superhet receivers radiate at the local oscillator's frequency (but not on the same frequency that the receiver is tuned to), but proper design usually completely isolates this from the antenna... this was one of the reasons for most receiver designs having at least one RF amp stage between the antenna and mixer in superhet radios.
I remember the TV detector vans, always just guessed they picked up the IF. Nowadays they just assume everyone has a TV and get shirty with people who genuinely don't (and hence don't have a license). But I've learnt at least two things about radios I didn't know, so thank you!
Your right, my old man doesnt have a tv and gets badgered continuously.
I've had problems with neighbours tv interference in the past on low freq's, I suspect its been the scanning coils, so maybe detector vans or mans can detect this also, its pretty powerfull on some sets.
Thing of the past now though.
It would be interesting to know exactly what they did detect. One of those questions that never quite leaves your mind. Well, my mind anyway, what's left of it...
Going off the fact they can tell what channel you are watching I think you were right IF frequencies, probably 2nd & 3rd video IF, I believe on old telly's they are the strongest signal, you'd need something really high gain topick this up from a distance though.
TV detector vans actually detected nothing. If you ever had the chance to look inside one (I did), They were empty. Nobody was ever prosecuted on evidence produced by these vehicles as none was ever produced. The whole idea was if you had no license and you saw the van in the area you go and buy one in panic.
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