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
| 