RadCom April 2024, Vol. 100, No. 4

34 April 2024 Regulars SAQ The SAQ Christmas transmission is a regular event and many VLF enthusiasts around the world tune in to 17.2kHz on Christmas morning to see if they can hear the characterful transmission from the 100-year- old alternator transmitter in Sweden. Obviously, the signal is easily received here in the UK but it is challenging to hear further afield. Gedas, W8BYA caught some traces of the transmission in Indiana as did Jay, W1VD in Connecticut, despite much QRN from an incoming storm. In total, there were 508 reports from around the world including eight from the USA, one from Argentina and one from Australia. Paul Nicholson in Todmorden has access to VLF receivers at four “Indian Lightning Detector Network” sites and reported that he could see traces at some sites but nothing audible was apparent. He then combined the four feeds together to form a phased array, compensating for the phase delay on each path and, with suitable adjustments, was able to extract the audio. I’d give it about 339. He also made a spectrogram of the optimised feed where you can clearly see the varying frequency of the mechanical transmitter ( Figure 1 ). There is a fascinating video of the Christmas broadcast on the station website [1] . I love the water- filled rheostats which control the alternator speed. 472kHz Malcolm, G4FQI finally got his troublesome 472kHz amplifier going again in January and pretty soon made it to W1FRV and K1BZ. W1FRV also copied G4CLO at 5300km. Malcolm’s receive capabilities seem good as he copied K9KFR on a few occasions at a distance of 6125km. In the middle of January, K8TV made an appearance for the first time on UK screens. His best distance on that occasion was to F6CWA at 6759km. One of the best spells of good propagation occurred in the small hours of 18 January with K8TV, W3TS, W2XAM, N9LB, WB8RJY, K3MF and KD2OM all being seen in the UK at various stations. In the West of Ireland, EI0CF also spotted WD9EKA, NV4X, N4TKW and K1BZ in addition to the ones seen in the UK. The end of January saw a drop in conditions with few transatlantic signals coming through until N4WLO was seen by G8AOE, G0FYD, GM3YXM and G4FQI around dawn on 30 January. His best distance on that occasion was to PA0RDT at 7532km. G4FQI and G0FYD also copied K9KFR on that day. Not many QSOs are made on 472kHz digital modes but I was pleased to have a JT9 contact with Steve, SO5AS in January. It proves that it’s worth keeping an eye on the WSJT-X waterfall to see if anyone is calling! In February conditions started to improve and Malcolm was getting reports from WA3U and W1FRV on 7 February. Malcolm’s signal also reached WA3U, so there’s a QSO opportunity there. Around this time, N4WLO was getting decodes from DL4RAJ (8277km) and from ZL2AFP at 12,365km. By the middle of the month, G4FQI, G4CLO, PA3GSH and DC0DX were all reaching W1FRV who is near the east coast of the USA, south of Boston. All of the above activity was on WSPR or FST4 but Graham, G0NBD is keeping the Opera flag flying and made some QRP transmissions with his barefoot IC- 7100 producing “just a few Watts.” His signals were reported by G0TKN, PA7EY, PA0RDT and LA3EQ. A shorter-range contact was a landmark event for Laurence, KL7L when he made the first Alaska-to- Alaska CW contact on 472kHz with Hudson, KL4LJ. They had problems with Hudson’s QRP Labs Tx but Laurence kept hearing an occasional keyed carrier. This turned out to be Hudson connecting his VNA across the coaxial cable feeding a few tens of metres of wire via a tuner. In the end, he managed to key the VNA and they exchanged reports of 559/599. Laurence was using his Monitor Sensors transverter throttled back to a few watts. They are only a few miles apart, but he says that the VNA QSO will stick with him for a long time! Talking of CW, Roy, G4CLO is keen to encourage some activity. He is often around after the Sunday morning net at about 9.30am or around 8pm on 473.0kHz. He’d be happy to arrange a sked – his email is OK on QRZ.com 136kHz Keeping an eye on the “Top DX Spots” posted by Roger, VK4YB, it is interesting to observe that 136kHz long-distance propagation seems more consistent than that on 472kHz. Some nights when 472kHz is only achieving 6000km or so, 136kHz is still hitting the 10,000km mark. This is despite the much greater difficulty in radiating a decent signal on the band. The best distances achieved recently were DL7NN to VK4YB (15,763km) and VK6MJM to KM5SW (16,165km). R2BM also made it to VK4YB at 14,038km. All of these amazing results came in late January and early February using FST4. The Opera mode is also in regular use on 136kHz with SO5AS being the most active European transmitter of the mode. VO1NA has also been received on 136kHz Opera by G4SDG, G0FYD, F5WK, LA3EQ and PA0RDT on this side of the pond before Christmas. VLF VO1NA has been running a beacon on 8.27kHz for a long time, enabling a record of propagation effects throughout the year to be logged by members of the DL0AO club station where the receivers are sited. Local weather seemed to be affecting the reception and Markus, DF6NM has been working on a solution in order to give more consistent results. One effect he noticed was, because the E-field antenna at DL0AO is surrounded by forest, sensitivity increased markedly in frosty weather and reduced in warm, damp conditions. They are now experimenting with an AGC system which attempts to equalise the E and H components from the two antennas (a 150m long ‘earth-dipole’ and an E-probe) so as to give more consistent results. Unfortunately, Joe’s transmission has been compromised by bad weather which snapped the halyards for his big antennas and he is now using a longer but lower wire which suffers more from tuning variations caused by the weather at his end. You can see various parts of the VLF spectrum on the DL0AO grabber site at [2] . References [1] https://alexander.n.se/en/ [2] https://vlf.u01.de/ LF Dave Pick, G3YXM daveyxm@gmail.com FIGURE 1: SAQ received by Indian Lightning Detector Network.