Hi Jeff and all, > But I do some longwave listening with my old Kenwood TS-850/HF > vertical and often hear European AM broadcast stations in the > 150-200 kHz range even from my QTH in Missouri. Radio France > Inter can often be heard from local sunset until > sunrise in Europe on 162 kHz. The BBC station on 198 kHz is > almost as loud. Interesting. This means that your S/N for these stations is somethinh like 3 dB in 5kHz bandwidth or perhaps better.
> It's easy to assume that these signals are spurs from > local AM stations but they make the very long trip using > immense power, often above a megawatt. Even very low > power 600-meter ham beacons around 500 kHz can be heard > over most of the U.S. Your observation that 1 MW will give a reasonable trans- atlantic signal in AM bandwidth means that 1W will give a reasonable signal in 5 mHz (milliHz) bandwidth. We can easily communicate with QRSS if Rx and Tx are frequency stable enough. Have a look at this page: http://sm5bsz.com/linuxdsp/usage/am1030.htm Figure 7 shows AM carriers at a bandwidth of 3 mHz. Look at the signals around 1029.9975 kHz. There is no question that amateur QRSS would be perfectly reliable as a transatlantic communication link. With 3mHz bandwidth each FFT would have to span a time of something like 600 seconds (with a sine squared window) For good QRSS one might need 5 waterfall lines for a Morse code dot. The speed would be one dot in half an hour. One would not be able to transmit more than one or two letters in a whole night. I could transmit a qrss "L" in 5 hours on a random frequency in the band. Everyone in EU or in the US with any interest could report back my frequency and signal level. Not really a QSO, but simple with existing hardware and software. We can however develop much smarter coding than Morse coded CW:-) > Don't sell longwave short. I do not follow the development, but I would guess interesting things already happen on 137 kHz. Now there will be two bands where really narrow bandwidth is possible. 73 Leif / SM5BSZ _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flexradio.com/ Homepage: http://www.flexradio.com/
