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Radio Amateurs Continue to Plumb the Spectral Depths


David Bowman, G0MRF, reports that he and Dave Riley, AA1A, have completed what is believed to be the first transatlantic contact on 630 meters since the MF band was released to US radio amateurs this past fall. They used JT9 digital mode to complete the more than 5,160 kilometer (approximately 3,200 miles) contact during the early hours of December 23.


On the UK end, G0MRF was running a modified Icom IC-7300 with a filtered preamp and a 60-W amplifier to a 250-foot wire configured as an inverted L. AA1A benefited from his near-Atlantic Coast location in Marshfield, Massachusetts, Bowman said.


Elsewhere, Dex McIntyre, W4DEX, continues to extend the limits of what is possible at VLF by achieving two significant results at 8.270 kHz. A record transatlantic message length of 42 characters resulted from an overnight transmission on December 25/26, received by Paul Nicholson in Todmorden, UK. The distance covered was 6,194 kilometers (approximately 3,840 miles), and the information rate of 24.6 bits/hour was reported to be about 70% of the channel capacity (signal bandwidth was 0.133 Hz).


The following night, a three-character message (“QRZ”) from W4DEX was received in Cumiana, Italy by Renato Romero, IK1QFK, achieving a new world-record distance of 7,173 kilometers (approximately 4,447 miles) for message decoding at VLF. The signal-to-noise ratio on the Italian end was on the order of –70 dB. W4DEX operated with an ERP of just 100 µW. The mode used was EbNaut coherent BPSK with transmitter and receivers phase locked to a GPS-derived timing signal. McIntyre needed no license to transmit in that region of the spectrum, since the FCC has not designated any allocations below 9 kHz — a region known as “the Dreamers’ Band.”


In June 2014, running on the order of 150 µW ERP, W4DEX transmitted the first sub 9-kHz transatlantic message by a radio amateur, also detected by Nicholson. W4DEX and IK1QFK already hold the world record distance for VLF signal detection, and this latest result extends that to message decoding.


In Newfoundland, inveterate VLF experimenter Joe Craig, VO1NA, has been transmitting the letter S using EbNaut, starting at 2100 UTC each evening on 8.2700075 kHz. Craig told ARRL that the very low power signal has been copied in England, Germany, Poland, Russia, and Italy, “where the guy who sent the first S across the pond was born!” Craig quipped. “I wonder what amazing things the new year will bring.” — Thanks to David Bowman, G0MRF; Paul Nicholson, and Joe Craig, VO1NA



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