LF: Re: Olivia 8 x 250 / psk31 / MFSK 8

["James Moritz" <james.moritz@btopenworld.com>]

Dear Graham, LF Group,

Monitored your beacon with 2 x Fldigi and 1 x Spectrum Lab. It is a bit hard 
to make a comparison, since the transmissions don't always overlap, and the 
signal level is constantly changing. (For future tests I would suggest a 
longer text would make for better comparison.) But the two modes seem 
roughly equivalent as far as likelihood of decoding successfully is 
concerned, although the MFSK8 has a faster throughput than Olivia, I think. 
Both were more or less 100% copy at the peaks of signal strength, and 
dropping out completely at the bottom of the dips. The QSB seems to be 
particularly fast at the moment, with signals sometimes dropping out 
completely and returning within 30s.
G4JNT says the Olivia signal looks brighter on a spectrogram... funny, for 
me it was the other way round...
BTW, re your earlier e-mail; both these modes are M-FSK modulation with 
constant amplitude (not if you TX both at the same time of course!), so no 
linear required in either case. PSK31 needs envelope shaping though.
Cheers, Jim Moritz
73 de M0BMU