Trasmissioni VLF a 8 KHz

Tratto dal gruppo:  [VLF] Natural Radio & VLF Group messages: .

1a.  VLF transmissions from IW4DXW From: Paul Nicholson Date: Thu, 28 Nov 2019 11:58:27 PST Riccardo has sent two EbNaut coherent BPSK messages recently from Ariano on 8270.003 Hz start: 2019-11-26_21:00:00 UT symbols: 15 seconds length: 13 characters CRC: 12 bits coding: 16K21A and start: 2019-11-28_08:00:00 UT symbols: 10 seconds length: 20 characters CRC: 24 bits coding: 16K21A Both messages decode here in Todmorden (distance 1413km), with Eb/N0 +1.3dB and -0.4dB respectively. At Cumiana (distance 371km), cross correlations reveals the signals at Eb/N0 -18dB and -6.0dB, too weak to decode. Bielefeld (845km) also too weak to decode with Eb/N0 -1.8dB and -8.1dB. The 2nd transmission might have decoded but the Bielefeld stream had one of its one-sample-backwards timing breaks. Each transmission lasts about 7.5 hours, the transmit power is only a few uW so a very narrow bandwidth has to be used. See http://abelian.org/ebnaut for info about the BPSK and coding scheme. GPS timing is essential if you want to receive these signals but that is very easy to set up. -- Paul Nicholson