How to set appropriate value for a FM receiver [LimeSDR-USB]?


#1

I begin to construct a FM receiver using limesdr-usb.


Now, a .grc file can been run. But I found that I’m not quite sure how to set appropriate parameter values (RF gain, IF gain, BB gain, Transition Width and so on) for a FM receiver.

I’ve tested a lot of values. There are usually heavy noises in the output. It is strange that the output is not as good as the RTL-SDR’s output (with the same gain value, as show in the above fig).

By the way, there is an interesting phenomenon. Every time I touching the receiving antenna, the noise decreased.

Without touching the receiving antenna: (there is a FM music station at 97.4M, but i can’t hear the music)

Touching the receiving antenna: (the station’s signal appears in the frequency spectrum, and I can hear music)


#2

Just replacing the original antenna by a thin wire, I can hear clear FM music.
So, I think the original antenna gain is too low (at least for a FM signal).


#3

A thin wire? what are you using, do you have a picture or description.


#4

OK.
Fig1: a straightened paper clip is used.

Fig2: A long wire is used. This one works better.