Last Updated on October 26, 2023 by John Berry
Modern data modes are powerful. This video on data modes describes just how powerful.
They are well aligned to the propagation mode for which they are intended – JT65 (and later, Q65) is suited to moonbounce communications while MSK144 is well suited to communications via meteor scatter.
The designers, led by Joe Taylor, K1JT, have recognised that for simple QSO-bagging, little information need be sent. Two callsigns and something about the signal reports and locations is all that’s needed to meet many needs. This reduction in information means two things.
First, the necessary RF bandwidth of the channel need only be very narrow. This means that the required signal to noise ratio is small – even negative. A bandwidth factor applies so that an improvement of anything up to 25dB can be had. So, the effect is that signals can be decoded well below the noise.
Second, since the information to be transmitted is meagre, and of the same form in all transmissions, source encoding is used to reduce the transmission to a 72-bit user message in each transmission cycle. Depending on the target propagation mode (such as meteor scatter), error detection, error correction and synchronisation is added. So, the result is further effective gain of up to 8dB.
And additional gain is available through averaging of multiple part receipts.
The result is the same as if you add a 10kW amplifier to a 1 Watt SSB phone transmitter, or if you add a 1MW amplifier to a 100W transmitter. The improvement in receiver threshold sensitivity and resulting system value is huge. Suddenly, for example, you can do moon-bounce (EME) with a modest antenna array.
DX – the seeking out of rare amateur stations at vast distance – is a central focus of many radio amateurs. Modern data modes materially affect the hobby by making rare not so rare, and shrinking distance. The outcome of such a revolution has been questioned by many in the hobby. They wonder “whither amateur radio”. If it all becomes too easy – like shooting fish in a barrel – where’s the fun.
Does it mean, for example, that the fun is in the GHz bands? Will the fun be in more esoteric propagation modes? Or in something else?
Simply, some love the new-found contacts, while others predict the hobby’s demise.
This video presentation illustrates that whilst the modern modes get close to the Shannon limit, they’re not there yet. So, is there more to be had? Or will the hobby spin off more great developments led by other elites like Joe Taylor?
Is the hobby dead, or just getting started? Watch this, and add to the debate.