Thursday, 26 March 2015

A 630m QRSS Test

A few days ago, the power of the slow speed QRSS mode was nicely demonstrated by Mark, VA7MM (Coquitlam, BC) and Jack, VA7JX (Campbell River, BC, on Vancouver Island).

Mark was transmitting on 630m at a power of just 144mW output, while Jack was receiving on his normal 630m inverted 'L'. Mark tried various QRSS speeds ranging from QRSS3 (3 second 'dits') to QRSS60 (60 second 'dits'). One can clearly see the difference between the three speeds.

Going from the relatively slow CW rate of 6 WPM to just QRSS3 alone, produces a healthy 12db increase in signal level. Going from there to QRSS10 produces another 5db, while going all the way to QRSS60 produces a whopping 24.8db over 6 WPM CW! The trade off, of course, being the amount of time it takes to send the needed information.

In practical terms, contacts can be made relatively quickly at both QRSS3 and QRSS10. After that it becomes a bit of a chore as conditions need to be very stable for long periods of time ... as well, you'll need several hours to complete a two-way exchange.



This is over a 120 mile (192km) path but what is remarkable is the rugged nature of the path as shown here:

Although mostly over water for the second portion, the initial launch of Mark's signal is into a hellish 60 mile path of rugged coastal mountain peaks, with most of them in the 3,000 - 4,000 foot range! If this is an all groundwave path, and I suspect that it may be, it surely demonstrates the amazing groundwave capability of 630m. If there were any skywave involved, I would expect to see some fading on the signal path ... but the QRSS60 signal looks rock-solid and fade-free.

I should add that Mark's transmitting antenna is very minimal at the moment, consisting of an 80m dipole fed as a vertical 'T', tuned but not impedance-matched and ... no ground radials. Pretty remarkable actually.

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