28 May 2015

DT puzzle

As you may recall, I use (very successfully) on 10m a WSPR-AXE-CW beacon by W5OLF.  In the last 6 months this has served me well.  However I was puzzled by a second report last night that both DT was way out (around 4.7) and the frequency was sometimes outside of the lower end of the WSPR sub-band. I decided to check DT locally using my FT817/PC as a receiver. Sure enough, DT was very high. Setting the clock to internet time -4 seconds made almost no difference. This evening I set my beacon TX frequency about 150Hz higher (adjusted the multi-turn pot) and, for reasons I do not understand, my DT has dropped to - 1.4 setting to internet time exactly on an even minute. It seems resetting the frequency has also fixed the DT issue. Perhaps this is something to do with Wolf's software? Anyway, I am now waiting for local Nick G4IKZ to confirm my DT findings.

UPDATE 2216z:  For reasons I do not claim to understand, I needed a long hard reset (mains power off for 20 secs) to get modulation to appear after a small frequency adjustment. All seems to be working now but the beacon will be on overnight to see if the modulation remains on.


Todd Dugdale said...

What is "DT"?

David (G0LRD) said...

'Delta Time' - It is a local measurement of the offset between the received WSPR message start time and the expected start time (even minute plus 1 second) according to the receiving PC's clock.

73 David G0LRD