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Technical description of the digimode: SIM_PSK 
Name of program: SIM_PSK
Development: 2014
Manufacturer: NIZAR BEN REJEB
Origin: Tunisia
Date of first issue: October 2014
Modes: BPSK 31 and 63bps (125 bps expected)
Modulation: DBPSK "Differential Binary Phase Shift Keying".
Pulse shape: Similar to the classic BPSK31.
Bandwidth : About 60 Hz
Demodulation: Coherent
Synchronization: On the signal
Correction of errors: FEC per character (Forward Error Correction)
Tolerates 1 bit of error per character
Convolution code: NO (makes synchronization too slow)
Interlaced: YES
Repetition : YES, but only for certain messages structured as CQCQ, QRZ, QRALOC, NOM, QTH,
Maximum drift: 20 Hz / min (depending on signal level)
Lower intelligibility limit: -15.5 dB in text mode, up to -17 dB in message mode
(In the presence of white noise over a bandwidth of 3 kHz)
Receiving mode: Indifferent (LSB or USB) Note: The frequency setting is simplified by remaining USB on all tapes
Character Set:
53 "fixed code" A..Z 0..9 <CR> <SPACE>. ,: = =? '()! / @ # *
No character reset to error or character waiting ().
Lower case characters are converted to uppercase,

Special characters: Special characters such as "" are converted to uppercase "standard" characters (in this example: "E") with the possibility of displaying in lowercase characters locally.
Posts: The messages used by radio amateurs are coded and structured.
Speed: 187 car / min (31.25 wpm)
Principle:
Coding "varicode" representing "structured" whole phrases.
SIM = S tructured I ntegrated M essage BPSK31.

Structure: Variable length coding, from 10 to 100 bits
According to the characters ... words ... sentences
Availability: Since October 2014 on www.on4nb.be/sim.htm.
Advantages

Optimized Varicode: more reliable thanks to the use of interlaced frames
Error correction: FEC.
Digital squelch based on the consistency of received signals.
Very fast transmission thanks to the coding of whole sentences.
Gain of 5 dB on an analog PSK (decodes signals imperceptible on a waterfall).
Split mode: use of a transmission frequency independent of the reception frequency (in the same band).
Centering automatically on the selected frequency with a click of the mouse.
Display of the "eye diagram".
No special installation.
Permanent evolution according to the demands of the OM's
Hyperlink to DX-cluster and PSK-Reporter:
(Real-time announcement via the internet of the presence of the station using SIM mode, and where it is received.)

+effective and auto contact abled
- not many people know about it.


Mode Menu
SIM31
Mode Audio Sample
FFT Window Screenshot
SIM31