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3

The 300 650 combination is often used for CW (Morse Code) reception. It tunes the SDR receiver’s (Tayloe mixer or FPGA or software synthesized) oscillator(s) 650 Hz below (or above for LSB) the dial frequency so that you will hear a 650 Hz beat frequency tone for RF signals transmitted at the dial frequency, and inserts a 300 Hz bandpass filter that cuts ...


3

SSB has a bandwith of roughly 2.7KHz. However, if you are listening to a station, but there is another station (or loud noise) overlapping with it slightly either below it or above it, you can narrow the receive bandwidth to try to clip off the interfering signal. The result will make the fidelity of the station you are listening to slightly worse, but ...


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Note that I am not a radio guy, but another possible explanation occurs to me: The signal might really be there but not coming from the station. Rather, radio receivers typically have an intermediate frequency that's used to make the signal easier to work with. Somebody nearby was listening to the radio station you were hearing and you're actually picking ...


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I know next to nothing about amateur radio, but I'd like to float a possible explanation. If someone in your area is broadcasting an unmodulated carrier somewhere in the FM broadcast band, and if the frequency of this carrier is 1.355 MHz above or below the sports station's frequency, won't you detect an FM signal way down at 1.355 MHz due to heterodyning? ...


3

Don't trust everything you see when using hardware well outside its design specifications. The R820T2 tuner chip inside the NESDR Mini 2 was meant to be a TV receiver, and its datasheet says it works between 42 and 1002 MHz. SDR dongles push it beyond those limits, but even NooElec only claims 25 - 1750 MHz "approximately". The signals you're ...


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I figured it out! I examined this chart provided by the government to see what the 1.355MHz frequency (and nearby frequencies) were allocated for: https://www.ntia.doc.gov/files/ntia/publications/january_2016_spectrum_wall_chart.pdf I see now, they are allocated for AM radio. As I mentioned, I am new to this, so I have always known AM radio stations to have ...


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Try disconnecting your antenna to see if its entering the radio via that path. Ethernet interference (at least 10/100) has a different profile I've covered here Hunting RFI with bars every 61 khz And gigabit is a bit more white-noise like. Try disconnecting the antenna when the rfi is again present to determine which path the rfi is taking to enter the radio,...


4

I notice you said 50 KILOhertz, not 50 hertz. Big difference, folks! You're picking up interference from some sort of electronic device that has a component producing a 50 kilohertz wave. Since this appears to be dead-on accurate down to a kilohertz or less, it's probably controlled by a quartz crystal. Any time a signal is produced at some frequency, there ...


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Mine was from my ethernet router in my radio room. It didn't show up on lower bands, but started across 20 meters, and on harmonics. Unplugging the router made the problem, but I couldn't operate 20 meters as long S the router was activated.


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I had the same problem......discovered it was my florescent house lights in which I have led replacement tubes.


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At first I'd have said it's Xmas lights or a SMPSU, but then the 50Hz part got me thinking and remembered that it's more likely to be Ethernet over Power line device, they are also known as PLT's. These create RF noise of all types all over the radio spectrum either all the way through constantly, or in little blocks that come and go. Some have radio ...


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Those equally spaced lines in the waterfall are very likely from EMI/RFI noise generated by modern electronics, often harmonics and/or intermodulation coming from DC-to-DC power converters. Could be something inside an LED light or lightbulb, USB charger, wall-wart switching power supply, computer peripheral or network hub, video monitor, solar panel, or ...


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