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Has anyone ever done this

D

DXER1

Guest
When ever I am going out of town with my parents, They have their radio tuned to a certain frequency, I will try to find the one frequency that will block their reception I will aim the antenna that is on my radio towards their antenna, it bugs the hell out of them but it is funny never-the-less. ;D
 
I remember doing that to my folks a number of times when growing up when AM radio was the craze. Fortunately that gene got bred out of the next lineage.
 
I remember doing this on a school bus field trip in 1971.

Offset by 455 khz for AM, 10.7 Mhz for FM.
 
Thats funny. I used to drive my parents crazy by doing that with the Television. I found that if I tuned to certain frequecies or TV channels, it would knock out the TV in the other room. I'd laugh myself silly while my dad was up twisting the knobs on the tv scratching his head trying to figure out what was wrong.
 
Indeed I have!!!! Glad to see I'm not the only loony willing to exploit the unusual (at least to the uninitiated) powers of IF. :D Unfortunately, my parents were fully aware of my general geekiness, and had figured out by the second time I tried it that I probably had something to do with it, even if they were unaware of precisely how it worked. ;) Nevertheless, it's still fun in public places, and under the right circumstances, the trick can be used in reverse (if you're REALLY nerdy) to determine whether a certain station is popular in your area. When a car drives by, if 103.3 is open in your area... tune to it, and a dead carrier will tell you whether your mark is listening to your local classic rocker on 92.5. (On FM, at least, the trick does seem to work "100 kHz off", as would be required where both radios tune only on odd 200 kHz increments as most U.S. radios do...)

BTW, never been able to get the AM to work. Can anyone walk me through anything that might be different from FM (eg having to be on one side or the other of the carrier frequency)?
 
Anyone have a chart with what frequencies will interfere with what? What about for TV frequencies? I use to do that all the time to my sister back when she was living at home both of our TVs were back to back on the same wall It would drive her nutts. And I would pick up what ever movies she was watching in her room If I had it tuned to channel 3. I still laugh everytime I think of that.
 
Generally, I think for AM you tune 450kHz or 455kHz (depending on the IF/LO in your radio - most portable analog tuners are 455kHz, and most portable digital tuners are 450kHz, at least the ones I've seen) BELOW the frequency the other radio is tuned to, and for FM it's 10.7MHz.

Anyone know how to do this for frequencies below 87.5+10.7MHz or 520+450kHz?
 
TFC -- You might want to try one of those FM radios that includes TV audio. If the VHF TV audio (channels 2-6, 54-88 MHz) is on the same band selector position as the FM, then I'm presuming it tunes using the same part of the circuit as FM reception does, meaning they probably have the same IF.
 
Grrrradio said:
Indeed I have!!!! Glad to see I'm not the only loony willing to exploit the unusual (at least to the uninitiated) powers of IF. :D Unfortunately, my parents were fully aware of my general geekiness, and had figured out by the second time I tried it that I probably had something to do with it, even if they were unaware of precisely how it worked. ;) Nevertheless, it's still fun in public places, and under the right circumstances, the trick can be used in reverse (if you're REALLY nerdy) to determine whether a certain station is popular in your area. When a car drives by, if 103.3 is open in your area... tune to it, and a dead carrier will tell you whether your mark is listening to your local classic rocker on 92.5. (On FM, at least, the trick does seem to work "100 kHz off", as would be required where both radios tune only on odd 200 kHz increments as most U.S. radios do...)

BTW, never been able to get the AM to work. Can anyone walk me through anything that might be different from FM (eg having to be on one side or the other of the carrier frequency)?
Click to expand...

I knew about being able to do it on FM, but I didn't know how it would work on AM or TV. It seems like I remember reading somewhere that this method was used somehow to determine what stations were most popular, maybe not for ratings, but for some other purpose, by logging what stations people had on in their cars. Does anyone know about that?
 
Grrrradio said:
TFC -- You might want to try one of those FM radios that includes TV audio. If the VHF TV audio (channels 2-6, 54-88 MHz) is on the same band selector position as the FM, then I'm presuming it tunes using the same part of the circuit as FM reception does, meaning they probably have the same IF.
Click to expand...

I have a digitally (display/PLL synthesized, not IBOC) tuned FM radio that can be set to tune the somewhat lower Japanese band - would that work?
 
tfcwings said:
Grrrradio said:
TFC -- You might want to try one of those FM radios that includes TV audio. If the VHF TV audio (channels 2-6, 54-88 MHz) is on the same band selector position as the FM, then I'm presuming it tunes using the same part of the circuit as FM reception does, meaning they probably have the same IF.
Click to expand...

I have a digitally (display/PLL synthesized, not IBOC) tuned FM radio that can be set to tune the somewhat lower Japanese band - would that work?
Click to expand...

It definitely would work - in fact it would work really well (assuming that yours goes down to 76.0, as my Sony does). Just subtract 10.7 or 10.8 from whatever station you want to block and you would be able to do it to every FM frequency on the US dial + the audio for TV channel 6 (87.7).

A standard FM tuner only goes down to 87.7 or 87.9 and so could only "play the trick" to FM stations above 98.5.
 
Anotherguy -- you may have been thinking about an experiment done with a receiver on a billboard a couple of years back. I think it MAY have been preliminary research for Arb's portable people meter, but my memory is somewhat hazy on this as well, as you can see...
 
Ah the memories of my mischievous childhood are being awakened. I'm not sure if it works on todays PLL radios, but on the old transistor radios, I would take an 8 ohm audio output transformer & feed audio into the 8 ohm side & place the primary in series with the + battery lead...mine didn't broadcast carriers...mine broadcasted audio. The fun I had with that set up... To this day, my kid brother still thinks he picked up Los Angeles on FM from Cincinnati....hehehe
 
It's a lot tougher on AM. The local oscillator doesn't seem to radiate nearly as well from within an AM radio. Plus, there is no "capture effect" to wipe another station off the dial -- the best you can do is cause a heterodyne whistle which is usually around 5kHz (because of the 455kHz offset).
 
FYI, if you have one of those AM/FM/TV audio radios, they usually combine TV channels 2 - 6 on the same selection as FM (effectively covering 54 - 108 MHz). You can wipe out any FM channel from 88 - 108 with one of those radios!
 
Philip J. Smith said:
It's a lot tougher on AM. The local oscillator doesn't seem to radiate nearly as well from within an AM radio. Plus, there is no "capture effect" to wipe another station off the dial -- the best you can do is cause a heterodyne whistle which is usually around 5kHz (because of the 455kHz offset).
Click to expand...

The Sony SRF-42 and the Panasonic RQ-SW10 and SW20 (both Pannies are digitally tuned (not the IBOC type)) have 450kHz filters. The Pans tune down to 520kHz, so I can "block" anything as low as 970 kHz. Is there a way to block station lower on the dial? or will I have to find some longwave tuner?
 
I use to do this with little toy walky talkies they would picked up the signal from a cordless telephone I could hear what someone was talking about.
 
Philip J. Smith said:
FYI, if you have one of those AM/FM/TV audio radios, they usually combine TV channels 2 - 6 on the same selection as FM (effectively covering 54 - 108 MHz). You can wipe out any FM channel from 88 - 108 with one of those radios!
Click to expand...

But Phillip, those radios only stop on the exact frequency for channels 2-6. They are not continuous (unless it's a rare analog version), they skip frequencies to tune the TV channels. As you need to tune to a pretty exact 10.7 or 10.8 MHz below the "target" station, the Walkman type TV sound radio will not work in the same way as a radio that tunes continuously from 76.0 to 107.9.
 
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