SAQ loud and clear on World Radio Day 15:00Z
SAQ is a mechanical low-frequency TX at 17.2kHz, designed in the 1920s to send telegraphy across the Atlantic, over an open-water route, to Riverhead, Long Island.
It’s quite a job to optimise reception for a signal that is on perhaps 30 minutes twice a year. Building on the reception last year I thought I would try and improve the SNR. This thing was originally designed to reach Radio City in Long Island, NY, so there’s a decent amount of grunt, although I don’t think they run the system flat out these days. The signal was received quite clearly
Obvious ways to improve things would be to reduce the noisy urban environment, and to narrow the detection bandwidth. At the moment I use SAQrx as described in the last post together with a ferrite rod antenna, tuned directly to 17.2kHz. I would say the pickup section is working fine, but the associated laptop has two problems. One is that it’s unwieldy, and the second is that it is a source of interference in its own right. I have observed a reduction in noise floor not running it off its mains supply, and for some reason touching the trackpad generated much QRM, either coupling the scanning signals out via my body or simply being noisy when activated.
Today SAQ said they would be tinkering around 12:00 UTC, and this extended period let me play with the signal without losing a shot at their main transmission. Getting the rig out of the house into the garden is worth a fair improvement in SNR. I also recorded the RF signal via the sound card set to 96kHz. This would let me develop a hardware receiver by playing out the RF signal, effectively a SAQ pantry transmitter although I’ll probably inject the signal directly at the point after the tuned circuit, after all I know that the recording came from the amplified output of the preselector made from the ferrite coil and cap.
and a close up of the coil
In the live chat on the yet to be live SAQ YT livestream there was a little bit about the tunng up procedure
Alexander SAQ Grimeton Friendship Association
We are turning hole punch strip reader on/off and trying to tune the transmitter by adjusting drive motor speed and antenna resonance frequency
And I got some of this. The UK is about 1200km away, a great circle map of Bristol to Halmstad which are the nearest airports show most of the distance is over water, and most of the land crossed is the UK. The comparison with JFK shows the original path was a very tough ask
An 8kHz sampled copy of the audio signal
It seems a little bit stronger than last time, perhaps SAQ’s tuning up earlier worked, or perhaps propagation is better today. And I have reduced the noise floor by getting out of the house. Here is last time, for comparison
I also received their line-up transmission at about 12:30 UTC
while helped me line up outside. I was reasonably pleased with the little ferrite rod antenna, signal was 598 to me, if my Morse were better I would say I could catch all of that, signal report 598 due to the slight wander on the tone, not surprising given the way it is generated. It was worth putting the laptop as far away as possible from the ferrite rod, that wasn’t so noticeable indoors with the generally higher QRM but was worth having outside. I will look at improving the design of the ferrite antenna for next time1, which is July 3.
Below is the SAQ livestreamed video of the alternator being started and the transmission
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Fortunately there are other VLF naval stations like GQD on 19.6kHz to test with ↩