Wasn't me. Ididn't hear anything on 4147 before I left for work this morning. Our groups test signal stopped at 07:00 CST and was centered around 7.2 MHz and covered 100 kHz and running 10 watts or so peak power for the signal. Four transmitters all at one location and trasnmitting a single data stream all synced together...on 4 different antennas. The date stream from each transmitter was not more than 6 kHz wide and consisted of a simple B&W picture with the station's call. Antennas were near ground folded dipoles with 3 counter poises for each FD. The feedpoint impedance was 50 ohms. Two antennas running N-S and two antennas running E-W. All 100 ft from the transmitter site. Four remote receivers located at 20, 50, 75 and 100 miles were used. All were receiving 100% copy of the data. Data sequence was 1 minute on and 5 minutes off each hour. Each transmission had a new data stream (picture).
The hardest thing was getting the antennas set up and deciding weather to use my call of that of one of the other 3 hams involved. There were a couple of dozen SSB and AM signals on top of my signal last night with at least a dozen QSOs that I could hear. Thanks to a rather large research firm for allowing us to use their equipment. The format was OFDM with interleaving as described in on the firms' web page. As far as I can tell, the results were the same as the firm's test on their test frequencies but they will have to run the received data in their lab as we were only recording the information. It was interesting to see if QRM affected the signal. Listening to the QSOs on band, no one seemed to notice the signal. The band faded about 04:00 local time. Talkback was on 75M SSB and via cell phone when 75 went out. I'd like to try the same set up with 5/10/15 WPM CW sometime. I have done this with 2 CW transmitters before but never 4 transmitters. And you need to do this when the band is not very occupied. Walt ________________________________ From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Robert Chudek - K0RC Sent: Monday, March 26, 2007 10:51 AM To: [email protected] Subject: [digitalradio] What's the roar? On 7147 KHz at about 14:00 UTC today there was a 10~12 KHz wide digital signal that was booming in. It's still there 2 hours later but only S-5 now. Can anyone tell me what this "noise" is about? It sounds almost at bad as the old Russian jamming signals from years gone by. 73 de Bob - KØRC in MN
