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mikaelnousiainen / RS41ng

Custom firmware for Vaisala RS41 and Graw DFM-17 radiosondes with support for amateur radio use. Ideal for tracking high-altitude balloons. Supported modes include APRS, Horus 4FSK mode, CATS, morse code (CW) and additional digital modes like WSPR and FT8 via Si5351.
GNU General Public License v2.0
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Reduce spectral splatter when transmitting 4FSK #49

Closed darksidelemm closed 10 months ago

darksidelemm commented 11 months ago

The use of OOK mode for sending 4FSK seems to be producing more transmitter sidebands than should be the case. The code where this is set is here: https://github.com/mikaelnousiainen/RS41ng/blob/main/src/radio_si4032.c#L73

Example of spectra with OOK mode:

Screen Shot 2023-07-29 at 09 26 10

.. and with the 'NONE' mode (currently used for RTTY):

Screen Shot 2023-07-29 at 09 27 22

I recommend changing modulation_type to SI4032_MODULATION_TYPE_NONE.

mikaelnousiainen commented 10 months ago

@darksidelemm Fixed in https://github.com/mikaelnousiainen/RS41ng/commit/84c7a7d6c134f88f89b639379c7b95534b203640