fscoles

It has to be a radio based on the superheterodyning (around since approx 1926) or similar having one or more IF (intermediate frequency) stages, which makes the rf stage of the radio also sensitive to incoming low frequency signals from the fob. Some superhets may work better than others, so if one radio doesn't work, try another one, etc. The really old TRF (Tuned Radio Frequency, which does not have an IF or LO (local oscillator) stages) will not work for this...so don't try using your antique radio. Some SWL receivers have from two to three IF stages, such as the popular/collectible Hammarlund HQ 180 & 180A models. And while we're on the subject of magical tricks with car fob's, I found that only in certain cases can you remotely lock and unlock and start your car from a fob that's sending its signal thru your cell phones from across the neighborhood or from another country...it all has to do with matching the cell phones' with the respective fob's various designed IF frequencies....so sometimes it works and sometimes it doesn't.

Papa Bear

Let me rephrase my question.
srp204 said: "This is also the way to check tv and other remote controllers." TV remote controls are infra-red and, as far as I know, don't emit radio frequencies to be received. I have never tried it so I can't verfy one way or the other but there is a big difference between an auto remote fob and a TV remote control.
fscoles, thank you for clarifying the technology but I knew how it worked as I am a retired electronics tech and my father was a ham radio operator before 1920.

fscoles

Yes PB, I understand, and the amazing thing is my XYL (aka "wife") of 34 yrs still puts up with me. The only reason I brought up the related topic of remotely starting & operating one's car from a distance via fob signal thru cell phones is that there's lots of misunderstandings on how these things actually work. As for the TV & "universal" remotes mentioned above, yes their actual controller signal is usually from an IR-type LED, but do any of them emit a significant signal RF field from any intermediate stages on their circuit boards, which might enable them to do what was stated above?? (to use them in troubleshooting for the existence of a signal from one's fob). I haven't tried it. Hmmm....maybe we should try measuring for RF signals from our cell phones, to determine if they actually could cause brain tumors, and so on, and so forth.

Papa Bear

Read you 5 X 5 .