New release of MULTIPSK (4.35) (RS41 radiosonde)

Patrick Lindecker

New release of MULTIPSK (4.36)


Pour les francophones: la version en français de ce message se trouve sur mon site ( Il suffit de cliquer sur le lien "Principales modifications (courriel avertissant de la sortie de la nouvelle version)".

Hello to all Ham and SWL,


The new release of MultiPSK (4.36) is on my Web site (
The mirror site is Earl's, N8KBR:

The MD5 signature of the downloaded MULTIPSK_setup.exe file to, possibly, check (with WinMD5 for example), that the downloading works without error, is equal to: 8b9669cf7cfda8abb14b53490dc309ee

Multipsk associated to Clock are freeware programs but with functions submitted to a licence (by user key).


The main improvements of MULTIPSK 4.36 are the following:


RS41 radiosondes decoding


The RS41 radiosonde is in service since 2014. It equips the weather balloons used in meteorology. It is a small box of 109 g, equiped with sensors, a GPS receiver (for its position) and a transmitter for data transmission, this one being done according to a mode poorly documented. It is possible to monitor these radiosondes up to a range of 600 km, according to the reception equipment, whereas the weather balloons can travel up to 300 km, in general. It has to be noted that the balloons launches are generally done at fixed time. One or two launches are done each day.


For Hams and SWL, the RS41 signal can be received:

·                     either from the discriminator output of a classical UHF FM receiver via a direct connection to the PC sound card. However, the receiver must have a large reception bandwidth due to the high modulation speed,

·                     or with a SdR receiver (FunCube Dongle, RTL SDR,...) and directly demodulated by Multipsk. It is the most simple solution.


Note: Multipsk decodes the radiosonde position but not the telemetry (temperature, pressure etc).


This mode is available for licencied copies, only (otherwise, the decoding is stopped after 5 minutes).


See general specifications further on.



Other improvements:

·                     In ALE400, possibility to fix the frequency.

For more details about the basic operations in ARQ FAE, download:




Note about translation of Multipsk.exe and Clock .exe:  the 4.35 version of Multipsk has been translated to Spanish by Joachin (EA4ZB), from French.






Description of the RS41 mode

Baud rate: 4800 symbols/second.

Modulation : GFSK ("Gaussian Frequency Shift Frequency")

Reception mode: FM

Bandwidth : about 5 KHz

Demodulation : not coherent

Synchronization for bits: automatic using the signal

Detection code: yes on a header of 64 bits

Interleaving : no

Scrambling: yes

Each RS41 frame of 320 or 518 bytes is composed of two sub-frames Reed Solomon at the format 255-231, with the power of the first root (b) at 0. So it can be fixed 24 bytes as a maximum.

The data part contains different blocks:

·                     a block frame number + sonde identifier, protected by a a checksum,

·                     a block date and time, protected by a a checksum,

·                     a block containing the position and the speed of the sonde, protected by a a checksum,

·                     other blocks relative to telemetry (not decoded by Multipsk).


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