Wednesday, November 04, 2009

No whispering for contacts

An interesting question was raised in the WSPR forum: If my WSPR beacon is received by another station, and I receive his beacon, can we claim a contact and exchange QSLs?

I had been thinking about this myself a couple of days before the question was raised. WSPR is a good mode for HF propagation studies but it has become a popular activity with people who like to see what can be achieved with very little power. It is also popular with those who have no opportunity to put up good antennas who find that despite this they can still experience the thrill of sending radio signals half way round the world. So it's easy to see why people would like to claim contacts using WSPR.

The answer given, with which I must reluctantly agree, is that no, reception of each other's beacons does not constitute a contact because the confirmation of contact is only sent via the internet and not over the radio. WSPRers can QSL reception reports if they want, but these cards should be treated as SWL reports not two-way QSOs, and will not be valid for awards.

There is a WSPR QSO mode, but I have hardly ever heard anyone using it. The reason, I suspect, is that it is fatally flawed and unusable. WSPR works in synchronized two-minute cycles, of which about one minute and 54 seconds is spent transmitting information. The information is not decoded in real-time, it is decoded after the transmission period is over. This means that in theory you have five seconds to react to seeing someone's CQ call and set up your reply to them.

In practise you have less than that, because it takes at least a couple of seconds before you see whose signals have been decoded. Sometimes you have literally less than no time, because if there are a lot of WSPR signals it can take the computer more than five seconds to decode everything that was heard. Because the start of transmission time is critical you would have to wait best part of two minutes before you could send your reply. By that time the other station, seeing no response, might send his CQ again so he won't receive your reply anyway. It's a test of patience that is likely to end in frustration and I'm not surprised that the QSO mode receives little use.

It's a shame, but I don't see a solution without speeding up the transmission period so it takes 1m45s, or rewriting the software so that it does at least a quick decode of stronger signals in real time. There are other JT modes that can be used for QSOs, though they don't work with such weak signals and are unlikely to get you round the world with 2 watts to a curtain rail on a day with no sunspots.

3 comments:

Jorge Luis - ki4SGU said...

I too would have to reluctantly agree that is not a bonafide QSO, and certainly not valid for credit towards any traditional AWARDS. But with the advent of eQSL et al, it would seem that a pseudo or virtual category could exist where the long standing practice and tradition of QSL exchange could take place in a diminished state. And even pAWARDs with extra value placed on low power or antenna handicap, etc. Why not it is a Hobby, not the bloody Olympics here.

As for the 2 minute window, I believe it is a remnant of the program's EME origins. I'll dig it up and learn up on it.

I would also humbly predict that based on my S/N ratios, anywhere that WSPR can establish a 2 way link a traditional Olivia QSO "could" take place, maybe we should try it.

Anonymous said...

I have, for a while, thought it was a pity that WSPR reports showing that 2 stations obviuosly hearing each other are not having a QSO in real time. This may not be realisable with signal to noise ratios in the order of -20dB or so with conventional modes. But quite often you see SNRs with a positive value. I would conclude from this that a CW or PSK31 contact should be possible for the path reported. So far I have not seen anyone mention that they have achieved a QSO first suggested by a WSPR report. Maybe food for thought?

As an aside, I have tonight been sampling a few pints of your local real ale brew from Jennings - Cockerhoop - here in West Bromwich. Very pleasant!

Cheers Ju;ian de MAurice G4DVM.

g4ilo said...

I think the JTxx modes would probably offer the best chance of a contact when WSPR is just making it. In the WSPR.net forum a couple of months ago Patrick F6IRF suggested using JT4A, but he abandoned this as he found results were poor. He then suggested trying JT65A, but I haven't seen any reports as to whether this was successful.