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VK1KW QRSS beacon on 2m 15/01/13

This article reports reception of a beacon transmission by VK1KW. The beacon is an A1 Morse code beacon keyed at 12WPM in the even minutes and the message "KW" at QRSS3 (3 second dits) in the odd minutes.

Fig 1:

Fig 1 shows the spectrum grabs from that show signal received mostly with Doppler indicating reflection from aircraft.

Though it takes some care to find the KW identification due to Doppler, short periods of propagation and dropouts, over the hour, it is unmistakably KW.

The identification is strong as a result of several factors:

The signal cannot be heard by ear, much less identified.

This message was identifiable at 5dB S/N in 0.25Hz effective noise bandwidth in Spectrum Lab, equivalent to:

A competent CW operator should be able to read a callsign down to -6dB S/N in 2kHz ENB. In this case, identification was possible 28dB lower in level than would be expected of the 12WPM CW ID.

The extended sensitivity can provide an early warning of improving propagation.

Keyer

The keyer is a quite simple keyer based on an AVR chip.

Fig 2:

Fig 2 shows the keyer hardware. This implementation of the Simple Morse beacon keyer is described at Another simple Morse beacon keyer - basic, but accurate.

Conclusions

A beacon with a composite message containing a QRSS identification can be identified well below the level at which a normal speed CW message can be decoded.

The extended sensitivity can provide an early warning of improving propagation.

Links / References

Simple Morse beacon keyer

Another simple Morse beacon keyer - basic, but accurate

Improving weak signal identification of FSK beacons

Changes

Version Date Description
1.01 15/01/2013 Initial.
1.02    
1.03    

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