New release of MULTIPSK (4.42) - DMR #Multipsk


Patrick Lindecker
 

New release of MULTIPSK (4.42)

 

Pour les francophones: la version en français de ce message se trouve sur mon site (http://f6cte.free.fr). 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 (4.42) is on my Web site (http://f6cte.free.fr/index_anglais.htm).
The mirror site is Earl's, N8KBR: https://www.paazig.net/f6cte/MULTIPSK_setup.exe

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: a5711021fe4d99e7f7b210b4a262e647

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

 

The main improvement of MULTIPSK 4.42 is the following:

 

Ham DMR decoding (but not the voice)

 

"DMR" is the acronym for "Digital Mobile Radio". The basic specifications of this mode are public (ETSI TS 102 361-1 to 3 for the "Tier II" protocol used by Hams), but any supplier can add supplementary functions. It is used in VHF and in UHF, mainly for voice communication but also for data communication. It is a mode for professionals but also used by amateurs (according to a precise organization). For Hams, it is spread in a world net by using, among other means, repeaters and Internet.

 

The amateur DMR communications are the sole object of the Multipsk decoding (professional communications are decoded but ignored). The DMR is considered as a "professional" mode by Multipsk (but the Ham decoding is not limited in time).

 

It is here only considered the data communication which summarizes to identifiers (callsigns+first names) and possible text messages (with some rare positions).

Example:

F9XYZ Michel (2088006 - France), via TG 20800 (YSF France) - Slot 1

F0ZZZ Yves (2083004 - France), via TG 20800 (YSF France) - Slot 1

 

Note: the voice communication decoding is excluded because it needs an AMBE+2 Codec (under a proprietary licence).

 

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

·                     either from the discriminator output of a classical VHF/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 simplest solution.

 

Here is the WEB address where you can know where all DMR repeaters are located, with their frequencies, for each country: https://www.repeaterbook.com/repeaters/niche/index.php?mode=DMR

 

This mode is in freeware, so without time limitation.

 

See general specifications below.

 

Other modification

 

·                     Possibility to automatically record  the pictures received in MFSK (16/32 or 64).

 

Note about translation of Multipsk.exe and Clock .exe:  the 4.41 version of Multipsk has been translated to Spanish by Joachin (EA4ZB), from French.

See: http://f6cte.free.fr/Translation_files.htm.

 

73

Patrick

 

Description of the DMR mode

Baud rate: 4800 (with 2 bits per symbol so 9600 bps)

 

Modulation : each double logic signal (dibit) directly modulates, through a root raised cosine filter (to reduce the bandwidth needed), the VHF or UHF frequency in 4FSK (on about +/- 4.5 KHz). So this signal is received in base band after FM demodulation.

 

Reception mode: FM

 

Character set : on 8 bits

 

Shape of pulse : root raised cosine filter (Alpha=0.2)

 

Bandwidth : about 9 KHz

 

Detection and synchronization code: yes on 48 bits.

 

Codes: many codes are used (Hamming, Turbo-codes, Golay, Reed-Solomon, CRC...)

 

Interleaving : yes

 

Scrambling: no

 

Transmission

 

For a DMR repeater, each 30 ms it is sent a burst of 264 bits (synchronization + data) followed by a 24 bits packet called "CACH" containing diverse pieces of information.

 

Each burst corresponds to a slot 1 or 2 and they are transmitted alternatively 121212... (TDMA system).

 

A simple DMR radio transmits, each 60 ms, only one burst of 264 bits out of 2, without CACH packet.

 

A burst can be a Voice one or a Data one, according to the synchronization code.

 

For about the interface between your PC and your transceiver, see the paper "HOW_TO_DO_DIRECT_DSTAR_BETWEEN_HAMs_Rev_A.pdf" located in the http://f6cte.free.fr/DSTAR.ZIP file, but taking into account only the reception part (no DRM transmission by Multipsk).