fm95/README.md

fm95

FM95 is a audio processor for FM, it does:

• Pre-Emphasis
• Low Pass Filtering
• Stereo
• Polar Stereo
• SCA
• BS412 (mpx power limiter, simplest implementation ever)

Supports these inputs:

• Audio (via Pulse)
• MPX (via Pulse, basically passthrough, i don't recommend this unless you have something else than rds or sca to modulate, you could run chimer95 via here)
• RDS (via Pulse, expects unmodulated RDS, stereo, left channel on 57 KHz, right on 66.5, rds95 is recommended here, in modulation this is inphase to the pilot)
• RDS2 (via Pulse, expects unmodulated RDS, stereo, left channel on 71.25 KHz, rigth on 76 KHz)
• SCA (via Pulse, by default on 67 khz with a 7 khz deviation)
• DARC (via Pulse, stereo, with one left clock channel [change when data is changed] and other one is data which is expected to be nrzi with bit 1 being 1 here, and bit 0 being -1)

and one output:

• MPX (via Pulse)

How to compile?

To compile you need cmake, liquid-dsp and libpulse-dev, if you have those then do these commands:

mkdir build
cd build
cmake ..
make

Done!

CPU Usage?

Should run completly fine on a pi 5, fine on a pi 3b (30% cpu, 45% with lpf)

Other Apps

FM95 also includes some other apps, such as chimer95 which generates GTS tones each half hour, and dcf95 which creates a DCF77 compatible signal, and vban95 now which is a buffered VBAN receiver

FM95 Calibration

FM95 features a calibration mode -V which instead of outputing the MPX just outputs a 400 hz tone, use that tone to match the deviation on your transmitter