Monitoring QRSS Transmissions
October, 2010
QRSS is a data transmission mode (or technique) that is used by radio amateurs to transmit messages at very low power (also known as QRPp). The QRSS method involves reducing the data rate of the transmission to an extremely low value - thus reducing the bandwidth occupied by the signal to a minimal amount. This, in combination with computers and long FFTs provide us the ability to detect the presence or absence of very weak signals visually and decode the data.
As usual, I'm very interested in anything radio - and so I've setup Spectrum Lab to monitor the 30m QRSS frequency (10140khz) with an ICOM IC-R75. It was tuned to 10.13815 Mhz USB, thus the AF Centre is at 1850hz (+/- about 100hz as the factory calibration isn't perfect). What follows are pages of spectrograms which visualize the data over a 24-ish-hour period. Each page presents a 3.75 hour period.
The spectrograms below were made on 25th October 2010. Timestamps are in EDST (UTC +11).
Unfortunately, the results weren't as good as I expected. Part of the reason has to do with my short antenna (12m, half-wave, feeding 25m coax run) and my poor location (elevated noise floors). Also, being in Australia, we're a bit away from the main QRSS action. It's a bit of a dissapointment, but at least there is some evidence that there are some QRSS transmissions happening. The thing is - these QRSS transmissions are buried in so much noise, it isn't apparent just by ear whether there is a transmission or not. The noise can be 30db over the signal, and still, if you send slow enough and spend enough time doing FFT - you can recover the signal. Maybe I'll be able to decode that WOLF signal by eye ... more to come!
Currently I've got the radio tuned to the 136khz QRSS subband of the 4000m band building some more spectrograms of this more challenging VLF band. Experiments continue ...
Update: Unfortunately my small antenna picks up nothing but noise on the 4km band. The interesting part is the noise - a lot of it is from switchmode supplies such as the one in mum's DVD player ... Attempts to decode the regular beacon have been quashed as it seems it's not being transmitted in JASON mode as first thought - this one seems to have half the number of tones. It could be a JT variant ... but I don't have access to the specs to decode it visually. The only decoders available are for live audio stream use only :(.