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General Asylum General audio topics that don't fit into specific categories. |
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General Asylum General audio topics that don't fit into specific categories. |
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In Reply to: Whatever dude posted by Awe-d-o-file on March 27, 2017 at 08:14:29:
30 feet from the antenna is not very far at all, considering how far away the TV transmitter is. A weak TV station might be 30 miles away, and signal strength scales by the inverse of distance squared. According to the FCC, the median effective radiated power for TV transmitters operating in the VHF high band is about 30kW. If you do the math, a 30kW RF source located 30 miles away will have about the same signal strength at the antenna as a 1 milliwatt source 30 feet away. 1mW is pretty noisy, but not unheard of. I've read through data sheets for lighting dimmers where the EIRP spec was stated as <1mW.
Another thing to consider is that AC wiring is not a good carrier of RF. There are problems getting powerline Ethernet to cross from one circuit to another on the same phase, and that's operating 1-2 orders of magnitude lower in frequency than broadcast TV. Finally, the power supply of your TV is designed to filter RF and provide clean DC to the receiver. Any RF present at the wall socket will certainly be heavily attenuated at the output of the supply.
So, one hypothesis is that your noise source is radiating RFI in the VHF band, which is reaching a device specifically designed to collect that energy (your antenna), which is feeding another device that is specifically designed to amplify it (your TV's receiver).
Another hypothesis is that your noise source is feeding VHF frequencies back through its power supply, and over lossy AC cabling, possibly also crossing circuits, and then is getting through your TV's power supply which is specifically designed to be quiet in the TV's reception bands.
The former seems a lot more likely to me. It may not be the right answer, but you are far from proving your hypothesis.
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Follow Ups
- You can't use an AM radio to sniff for noise in the VHF band - Dave_K 11:08:37 03/28/17 (0)
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