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Date: Tue, 21 Dec 1999 11:23:30
To: rsgb_lf_group@blacksheep.org
From: "Rik Strobbe" <rik.strobbe@fys.kuleuven.ac.be>
Subject: Re: LF: qrss
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Hello Malcolm,

>Can anyone explain to me why qrss is necessary on 136 khz. All the
>activity that I have heard on this frequency is workable on normal speed
>cw at my qth.
With Gram (if used properly) you can easily 'see' signals that are 15 to
20dB below the audible level. It is a physical law that SNR is inverse
proportional to bandwidth. Practical bandwidth for 'copy by ear' is 30 to
50Hz, with QRSS you can achieve a bandwidth below 1Hz.
Last sunday I had a QRSS/DFCW QSO with G0MRF, his signal was completey
inaudible.

>I could understand the use of this mode on 20 khz and below because of a 
>possible bandwith consideration. If this was the case,  there are other 
>alternatives like MSK. Commercial stations only use the qrss method as a 
>necessity on VLF.
We have other limitations than the commercials, besides the legal 1W ERP
limit a lot of us are rather limited regarding antenna dimensions (=
antenna efficiency) and in a lot of countries there is also a TX output
limit (20W in DL, 100W in OH, 400W in PA etc...). This limits the ERP of
many stations to 100mW or less.

>I have not seen any weak signals on qrss that I could not copy aurally.
Maybe you have to experiment a bit with the setting of the software you use
for QRSS.

73, Rik  ON7YD