TV causing interference on radio

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mark32

mark32

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Currently in NJ
Hi,

The boss asked why when he turns on his tv (Outdoors) it causes interference on his nearby radio. Says it was fine last year but now this problem has surfaced.
 
mark32 said:
Hi,

The boss asked why when he turns on his tv (Outdoors) it causes interference on his nearby radio. Says it was fine last year but now this problem has surfaced.
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Tell him to tune in FM. He is hearing the 60hz tranny in the TV on AM.
 
Just about every electrical device sold has an FCC statement somewhere on it that says two things. This device may not cause interference, and it may recieve interference that causes undesirable operation.
In essence, it says "Tough Cookies!"
 
mark32 said:
...when he turns on his tv (Outdoors) it causes interference on his nearby radio. Says it was fine last year but now this problem has surfaced.
Click to expand...
Radio interference is on FM?

WAG
Both the TV and the FM radio have 10.7Mhz IF. Something cracked/broke/changed in the TV/radio. The radio IF amp is now picking up the TV IF signal.

carl
 
Thanks guys,

The boss mentioned that he temporarily replaced a cable, which one I don't recall as I was busy during the conversation, but said the interference went away. I never got into electronics so I don't know what an IF is, I just assumed that something happened to some of the equipment after spending the winter outside.
 
080527-1232 EST

mark32:

IF refers to intermediate frequency. It is very hard to do all your RF amplification at the incoming carrier frequency. This requires a variable tuning circuit for each stage of amplification.

If one has a tunable oscillator that can be mixed with the incoming signal, then a new signal can be generated that contains the information of the original but at a frequency that is the difference of the incoming signal and the oscillator, the IF frequency. It is easier to build a fixed frequency IF amplifier than a tunable one. Sometimes two conversions are done and this is called double conversion.

It is a very long time since I played with IF frequencies. The 10.7 mHz may be correct for FM, but I believe TV used a higher frequency. In standard TV broadcasting of times past the audio of the TV signal was 4.5 mHz from the video carrier. In the early days two separate IF amplifiers were used. One for video and the other for audio, but the same tuner oscillator was used.

Then someone realized that the 4.5 mHz audio carrier could be a considered a carrier on top of the video and maybe by the early 50s the switch was made to a single IF amplifier with an FM discriminator tuned to 4.5 mHz from the demodulated signal from the IF. This reduced a big problem with RF tuner oscillator drift and constant retuning to maintain good audio quality.

.
 
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I just assumed that something happened to some of the equipment after spending the winter outside.

Now I can see where this is coming from. He left equipment outdoors for the winter??

-Hal
 
hbiss said:
He left equipment outdoors for the winter??
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Chilly_Willy.jpg


"Does that matter?"​
 
Just about every electrical device sold has an FCC statement somewhere on it that says two things. This device may not cause interference, and it may recieve interference that causes undesirable operation.
Click to expand...

Don't make me laugh.

"Most favored nation" trumps the FCC requirement every time.

Check out the problems with electric blankets, battery chargers, dimmer switches, aquarium heaters, etc....the list goes on.

All I can say is 'good luck, Pilgrim'.
 
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