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From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
References: <004f01c9809a$708b5c30$0301a8c0@mal769a60aa920>, <497F3902.1070604@sighthound.demon.co.uk> <497F5976.5945.1B872C2@v.d.heide.on-line.de>
In-Reply-To: <497F5976.5945.1B872C2@v.d.heide.on-line.de>
Date: Tue, 27 Jan 2009 20:59:10 -0000
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Subject: Re: LF: PROPAGATION WSPR
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Dear Klaus, Mal, LF Group,

As far as being able to provide the information required in a beacon signal, 
I think WSPR and QRSS3 are roughly equivalent - they will function with 
similar signal and broadband noise levels at the receiver, WSPR gives a 
faster data rate, but QRSS3 requires less bandwidth, probably an advantage 
when narrow band QRM is present. Both have been used successfully as beacon 
signals. But at the moment, there is no QRSS equivalent of the WSPR beacon 
software. This means there are important practical advantages to WSPR.

The first thing is that the process is automated. The signal is transmitted, 
received, decoded, SNR is measured, and the result uploaded to a searchable 
database, along with every other reception report from all participating 
stations, so the information is available to anyone in almost real time in a 
very convenient form. This happens by individual stations setting up a 
transceiver, running the software, and connecting their PC to the internet 
(Oh, and remembering to enter their station info in place of K1JT's!). So it 
is very simple to add your station to a network of beacons, and access the 
data generated by the network.

Using QRSS beacons, the nearest equivalents are the "grabbers", which are a 
bit more involved to set up. The signals currently have to be interpreted 
visually; with QRSS3, this requires reviewing 100+ images, each with 
potentially several signals for an overnight monitoring session, either as 
they are generated or the next day, a tedious process. Then a report has to 
be manually written and sent to everyone who might be interested. Visually 
assessing SNR from this type of image is not very objective at all (hence 
the "T M O" reporting system). This sort of thing can be done in software 
(there are plently of CW-reading programs, Spectrum Lab has rather good 
facilities for calculating SNR), but it does not exist in an easy-to-use 
package

Furthermore, with WSPR each beacon station can transmit and receive during a 
session, which roughly doubles the number of stations in the network, 
effectively . The availability of a large number of "channels", with 
transmit and receive intervals of fixed duration, but randomised occurence, 
means that little is required to set up the network other than to know what 
frequency range is going to be used. One could imagine something equivalent 
for QRSS beacons, but again it does not exist in a convenient form yet.

Finally, if a single WSPR transmission is decoded, you have a useful amount 
of information - station ID, power, location, signal to noise ratio, without 
any prior knowledge of the station, or other channel of communication. With 
QRSS3 beacons, you usually only get a callsign (or part of one). No reason 
you should not send the other data in QRSS3 as well, but it would take a 
relatively long time to get the complete message, requiring longer "peak" 
conditions for a marginal signal. In practice, you are often relying on QRSS 
beacons station publicising their details on the internet in order to 
positively identify them.

So overall, from a theoretical point of view, I don't suppose there are 
particularly great advantages to a WSPR beacon over a QRSS3 beacon. But in 
practice, WSPR as a package is quite easy and convenient to use and gives 
useful results with achievable power levels, at least on 500kHz. It also 
allows one to get a good night's sleep! There are clearly bug-fixes and 
improvements that could be made to WSPR, or other modes, but at the moment 
it is an example of the maxim "I don't want it perfect, I want it Tuesday!"

Cheers, Jim Moritz
73 de M0BMU


----- Original Message ----- 
From: "Klaus von der Heide" <v.d.heide@on-line.de>
To: <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, January 27, 2009 5:59 PM
Subject: Re: LF: PROPAGATION WSPR


>
> Dear LF Group,
>
> we should clearly differenciate between all aspects.
>
> A propagation study does not need any information transfer
> via the radio path other than confidence on the identity of
> the station in focus. In that case, observing the carrier
> is best. So WSPR has no advantage over QRSS.
>
> On the other hand, WSPR has the advantage of automatic
> recording. But that is not an advantage of the mode, it
> simply is the lack of a corresponding simple program that
> does the same with a QRSS signal.
>