Clever idea - the RBW is a few kHz, and it’s not particularly sensitive (i.e. somewhere between -10 and 0 dBm is S21 of 0). Noise floor is around -80 dB (on S21 log mag), so you’d need -60 dBm into the receiver to see anything.
I’m not sure a TV or FM station would have that much power in a 5 kHz BW. TV is spread over 5-6 MHz. Say an EIRP of 1 MW at 100 MHz 10 km away = +90 dBm -32.44 - 40 - 20 = about 0dBm, and the RBW is about -30dB of the signal BW. So you would see that. But 10 km is pretty close (which is why nobody in Pasadena needs a TV antenna - a paper clip in the antenna connector is plenty). And 100 MHz is the middle of the FM band, where EIRPs aren’t 1 MW, like they are for TV.
I note that when I was running two NanoVNAs back to back with a SMA T (to try making full 4 parameter measurements at one time), you could see the other NanoVNA sweep across the receiver occasionally (a big spike in apparent S21), if they were both sweeping.
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On Dec 2, 2024, at 06:11, jskinner58@... wrote:
I realize this hardware is not made for this and results will be poor but I want to give it a shot anyway. New user of the H4 version. Looking to get some idea of signal strength of some local FM and TV stations. I tried setting the start and stop freq for the FM band and looking at logmag of S21 and got nothing - just an almost flat line near the bottom of the screen. Thinking I am missing a few settings. I have searched and read some but haven't found a complete list of settings needed. If I need to do this as some smaller freq bands I could do that.
