----- Original Message -----
From: "James Moritz" <[email protected]>
To: <[email protected]>
Sent: Sunday, December 28, 2008 12:19 PM
Subject: LF: Re: WSPR and CW
Dear Klaus, Laurence, LF Group,
I have been doing some experiments with WSPR on 2 PCs linked by audio
cables. I would certainly agree with KL1X about the importance of clock
accuracy - I found that an error of 5 seconds was enough to completely
prevent decoding. Fortunately, the clock on my shack PC is accurate enough
that setting it against an MSF-controlled clock once every several hours
is
OK. I also found that the "QSO version" of WSPR in WSJT 7 and the WSPR
1.01
beacon software will correctly decode each other's signals, although in
either case the QSO mode requires reception of all the overs of the QSO in
order to display the callsigns, due to the format used. When using the
beacon software for reception, be aware that it may take some minutes for
the decode to appear after the signal has been received - this seems to be
due to the "off line" nature of the signal processing used.
Recent experience here is that the WSPR mode offers advantages compared to
CW, either manual or QRSS, on the 500kHz band due to the low SNR and the
fading experienced. Many signals are either always below the audible
noise,
or not audible for long enough for aural CW copy without large numbers of
repeats. With QRSS, and a sufficiently long dot period, one can indeed
detect very weak signals, but the fading often prevents receiving, for
example, a complete callsign without losing some symbols and so also
requiring repeats. QRSS works much better on 136k, where the fading period
is much longer.
WSPR certainly decodes signals that are too weak for aural reception. In
sensitivity terms, I think it is comparable to QRSS 3. WSPR has the
advantage over QRSS 3 that the message duration is shorter. The 2 minute
transmission period of WSPR is a reasonable match to the fading period
experienced on 500kHz, so there is a good chance of sending the message
successfully before the signal fades out.
JIM
YOU OBVIOUSLY HAVE NOT SEEN MY REPORTS RECENTLY.
I OFTEN COPY THE USA STATIONS AUDIBLE AND LOUD ON CW AS WELL AS THE QRS3
TRANSMSSIONS.
WHEN YOU WERE STRUGGLING A FEW NIGHTS AGO ON WSPR I WAS SEEING THE SIGNAL
TRACE SOLID INSPITE OF SOME SLOW QSB AND HAD XGR/2 BEEN ON QRS3 I CERTAINLY
COULD HAVE HAD A QSO AS I DID A COUPLE OF NIGHTS LATER, XGR/2 OOO COPY.
This is the situation at my QTH obviously your RX set up needs tweaking. An
other disadvantage of wspr is the accurate time sync required for a decode
plus frequency accuracy, NOT the case with ON/OFF keyed morse slow or fast.
All things considered there is nothing to date to beat CW in its many
formats.
On the HF bands I have noticed an increase in hand sent and auto CW
commercial acty, CW is certainly not going away, and during contests on the
amateur bands one can hardly find a slot to TX.
There are digital modes also about but they seem to be slow at overtaking
CW, most are obviously not convinced.
mal/g3lev
I have yet to see any readable
trans-atlantic CW or QRSS signals at this QTH, while copy of WE2XGR//2
using
WSPR was reasonably consistent, producing a decode for about 25% of the
transmissions. The redundancy in the data should also make WSPR relatively
resistant to errors caused by QRN impulses, although the QRN level has
been
low here recently. For beacon purposes, WSPR also has the huge advantage
that reception, logging and reporting is automated, so the operator can go
to bed sometimes!
While WSPR does work well, I don't think it is the final word in LF/MF
digital modes - In particular, the information in a QSO is largely
restricted to "rubber stamp" exchanges. So I will certainly be interested
in
trying other modes, and look forward to see the results of Klaus' work.
Cheers, Jim Moritz
73 de M0BMU
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