I set up all the blocks and they work perfectly using a .wav file but I’m trying to host a talk radio and while the audio source shows my voice in the microphone input nothing comes out the speaker. What’s wrong? *See flow graph below.
With a .wav file, I would expect to see voltages in the range + - 1.0. out of the source.
Add a tool and see if the microphone is giving you + - 1.0. out of the source.
If you are using a standard broadcast FM receiver, you need to use a wideband FM rather than narrowband FM modulation scheme. NBFM is either 2.5kHz peak deviation or 3kHz peak deviation (depending upon it being really narrow or just narrow), and broadcast is a peak of 75kHz. If you are only deviating 2.5kHz you going to be really quiet on a broadcast receiver.
It’s possible your wav file is giving you more signal input than the microphone, and thus is louder than the mic, but it’s still going to be low if you are too narrow on your modulation.
Settings are all wrong/different:
- in Lime Sink TX RF freq is 12MHz (HF?) but in GUI FFT 446.094MHz (UHF?)
- add Float multiplier after Audio source (Mic must be Default input)
Ok I did that and it worked. Now just wondering how to get rid of the white noise and make the voice higher quality?
Putting a low pass filter on it should help remove the white noise - if you are only interested in voice, you can set the corner frequency pretty low (5000 hz or less)
If you are getting a lot of white noise, you may not have enough signal. What is your output level, and what kind of antenna are you using on the TX path? Also, why are you taking your sample rate to such a high level on the hardware? IIRC you should be able to feed the 480kSample/sec from the modulator directly into the hardware; adding the interpolater is just making work for everybody.