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48 lines
1.4 KiB
Markdown
48 lines
1.4 KiB
Markdown
# fm95
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FM95 is a audio processor for FM, it does:
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- Pre-Emphasis
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- Low Pass Filtering
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- Stereo
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- Polar Stereo
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- SCA
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- BS412 (mpx power limiter, simplest implementation ever)
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Supports these inputs:
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- Audio (via Pulse)
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- 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)
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- 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)
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- SCA (via Pulse, by default on 67 khz with a 7 khz deviation)
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- 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)
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and one output:
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- MPX (via Pulse)
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## How to compile?
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To compile you need `cmake`, `liquid-dsp` and `libpulse-dev`, if you have those then do these commands:
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```bash
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mkdir build
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cd build
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cmake ..
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make
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```
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Done!
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## CPU Usage?
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Should run completly fine on a pi 5, fine on a pi 3b (30% cpu, 45% with lpf)
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## Other Apps
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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
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## FM95 Calibration
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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
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