|
Stefan, LF,
very nice! Thanks for the link to the UA0SNV
monitor.
Yes if there is fading during the sequence this
will widen the carrier, just like any other amplitude or phase
modulation. For medium distances with multiple skywave modes, fading
periods on LF could be on the order of 10 to 20
minutes, equivalent to a millihertz or two. Longer paths tend to
be more stable with slower fading because the steep skywave components
have died out.
But keep in mind that a wider peak might also
have been caused by a small receiver drift.
BTW In my other posting I hadn't explained the
last dB number in the opds result line. This describes the quality of the
match to the callsign template, ie how many dBs the highest peak in the
cross-correlation function exceeds its average power, which
comes from noise and autocorrelation sidelobes. The range is from
about 22 dB for a perfect signal, down to a chosen threshold of 15 dB where
false positives start to appear occasionally.
I also intend to send more Op-32 later tonight.
All the best,
Markus (DF6NM)
Sent: Saturday, October 19, 2013 9:11 PM
Subject: Re: LF: T/A OPDS
Markus and OPDS fans,
On the page of UA0SNV,
http://dl.dropboxusercontent.com/u/76751319/opds32.txt
i just found this text:
UA0SNV OO18JB Opera-32 correlation http://df6nm.bplaced.net/opera/opds.zip
date time call distance frequency bandwidth snr correlation
2013-10-19 19:00:33 DK7FC 5745km 137560.111Hz 5mHz -49.1dBOp 81% 15.7dB
2013-10-19 18:20:32 DK7FC 5745km 137560.110Hz 5mHz -44.1dBOp 100% 19.1dB
So
it also works over the land path of that distance.
It appears to me that,
if the transmitted coherent signal and the receiver is stable, the x-mHz reading
says something about the phase stability of the path (?).
Markus, good
luck! In an hour or so i willy QSY to 472 kHz CW but will be back at
night.
73, Stefan/DK7FC
|
|
