By request, I have added a MEPT SKED page at http://www.obriensweb.com/sked
click on MEPT and join the experimenting... with 6hz wide signals ! Andy k3UK -- In digitalradio@yahoogroups.com, "Andrew O'Brien" <[EMAIL PROTECTED]> wrote: > > > From: Joe Taylor, K1JT > Subject: New software for MEPT > Date: March 9, 2008 > > About two weeks ago Murray Greenman, ZL1BPU, wrote to me suggesting > that I consider adding a mode optimized for MEPT to my software > package WSJT. I expressed interest in the idea, and we exchanged a > few emails about possible specifications. Then I sat down and wrote > out some detailed specs, and finally got busy and wrote a bare-bones > program implementing the new mode. > > I write now to let you know that an early realease of the program is > ready for testing. > > The program's provisional name is MEPT_JT. At present it is a > stand-alone executable, independent of WSJT. It is functional for > both transmitting and receiving, but it has no frills -- no graphics, > no GUI, etc. It is executed from a Windows command prompt. Like > WSJT, MEPT_JT uses a computer sound card to generate audio tones to > modulate an SSB transceiver operating on the upper sideband. In > receive mode the sound card digitizes audio from the transceiver. The > program scans a 200 Hz passband (the "QRSS window") looking for > MEPT_JT signals, and decodes them. Basic operating instructions for > the initial release can be found in the file MEPT_Instructions.TXT at > http://physics.princeton.edu/pulsar/K1JT/MEPT_Instructions.TXT . > > The basic specifications of MEPT_JT are as follows: > > 1. Transmitted message: callsign + 4-character-locator + dBm > Example: "K1JT FN20 30" > > 2. Message length after lossless compression: 50 bits (28 bits > for callsign, 15 for locator, 7 for power level). > > 3. Long-constraint convolutional FEC with K=32, r=1/2. > > 4. Number of channel symbols: nsym = (50+31)*2 = 162. > > 5. Modulation: continuous phase 4-FSK. > > 6. Synchronization: 162-bit pseudo-random sync vector. > > 7. Data structure: each channel symbol conveys one sync bit and one > data bit. > > 8. Keying rate: 12000/8192 = 1.46 baud. > > 9. Duration of transmission: 162*8192/12000 = 110.6 s. > > 10. Transmissions start two seconds into an even UTC minute: i.e., at > hh:00:02, hh:02:02, ... > > 10. Occupied bandwidth: 6 Hz > > 11. Minimum S/N for reception: around -27 dB on the WSJT scale (2500 > Hz reference bandwidth). > > You can run Argo, Spectran, or WSJT at the same time as MEPT_JT, in > order to provide a waterfall spectral display. > > In normal operation MEPT_JT displays information every two minutes and > is silent otherwise. In transmit mode in prints a single line when a > new transmission starts. In receive mode the program looks for > detectable MEPT_JT signals in a 200 Hz passband, decodes them, and > displays the results. If nothing is decoded, nothing will be printed. > > Like JT65, MEPT_JT includes very efficient data compression and strong > forward error correction. Received messages are nearly always exactly > the same as the transmitted message, or else they are left blank. > > Version 0.2 of MEPT_JT is functional -- and extremely sensitive -- but > the user interface is rough in many places. Suggestions for > improvements will be most welcome! Can anyone come up with a better > name for the program? > > Please email all suggestions to k1jt at arrl dot net. > > -- 73, Joe, K1JT >
