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CT2KCK > WW 14.04.16 19:16l 75 Lines 3848 Bytes #999 (0) @ WW
BID : 3425_CT2KCK
Read: GUEST
Subj: New DIGI Mode SIM31
Path: IZ3LSV<IK6IHL<IK7NXU<IW7BFZ<I3XTY<I0OJJ<GB7CIP<LU4ECL<CT1ENI<CT2KCK
Sent: 160414/1810Z 3425@CT2KCK.CTLX.PRT.EU BPQ1.4.65
SIM31 New PSK Digital Mode by Nizar
Web Page AT: http://www.on4nb.be/sim31.htm
...But why should anyone use a new digimode?
When listening this mode, it seems very close of the PSK mode, and indeed it is a BPSK varicode completely modified.
So to be able to recognize and begin a QSO, it was necessary to add at the beginning of transmission, a signal to recognize
it among other modes.
We chose to transmit the signal "SIM" in CW. This morse code can be disabled during QSO.
You guessed it, the goal of this new mode is not to do exactly as the PSK, but to make the decoding more robust,
more efficient when reception is weak or distorted by difficult propagation conditions (QRN, QRM, QSB ...).
This goal is achieved since tests have shown that this software is able to surpass the sensitivity of other known programs,
thanks to an enhanced decoding, and a better reliability by giving each integrated macro, its own varicode.
All this makes it possible to transmit more quickly and with less risks of errors.
This method should be particularly suitable for any QSO in QRP mode and for DX.
The program is now available and also an history of improvements.
Description of new digimode: SIM_PSK
Name of software: SIM_PSK
Development: 2014
Conceived by : NIZAR BEN REJEB
Origine : Tunisia.
First Issue: October 2014
Modes : BPSK 31 and 63 bps (125 also foreseen ).
Modulation : DBPSK « Differential Binary Phase Shift Keying ».
Pulse shape : Similar to classic BPSK31
Bandwidth : About 60 Hz
Demodulation : Coherent demodulation
Synchronization : automatic on signal
Error correction : FEC (Forward Error Correction)
tolerates one error bit per character
Convolution code : NO (it makes the synchronization too slow)
Interleaved: YES
Repetition : YES, but only for some messages structured as CQCQ, QRZ, QRALOC, NOM, QTH,
Drift tolerance : 20 Hz/min (depending on signal level)
Lower limit of intelligibility: -15.5 dB in text mode. Until -17dB in message mode (in presence of white noise with a bandwidth of 3 kHz)
Reception mode : indifferent (LSB or USB) Note: The frequency adjustment is simplified by staying in USB on all bands
Characters set :
53 "fixed code" A..Z 0..9 <CR> <SPACE> . , : - = + ? ' ( ) ! / @ # *
No character reset on error nor wait character (). Lowercase characters are converted to uppercase,
Special Characters : The special characters such as "É" are converted into standard capitals
characters (in this example: "E") but can be displayed in lowercases locally
Messages: The messages used by the ham-radio are coded and structured.
Speed : 187 char/min ( or 31.25 wpm)
Principle :
"varicode" able to encode characters, words and full sentences.
S I M = Structured Integrated Message BPSK31.
Structure : variable code length, from 10 to 100 bits
according to characters… words… sentences.
Software availability since October 2014 on www.on4nb.be/sim.htm .
Advantages :
Varicode optimized : less sensitive to noises by the use of interleaved fields
Error Correction: by FEC (Forward error correction).
Digital Squelch based on signals coherence.
Very fast transmission due to coding whole sentences.
Gain of 5 dB on an analog PSK (decoding of signals imperceptible on a waterfall).
Mode "split", allowing to use an independent frequency, for receiving and transmission (in the same band).
Automatic centering on the selected frequency, by a mouse click.
Displaying the "Eye diagram".
No special installation. Just copy the exe file or, if necessary, copy / unzip the .RAR file, and paste it where you want .
Permanent evolution, responding to users requests.
Hyperlink to "DX Cluster" and "PSK-reporter." announcing in real time via Internet the presence of the station using the
SIM mode, and where it is received.
All Text Transcrit from http://www.on4nb.be/sim31.htm site..
73´s from CT2KCK
Op. Paulo
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