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Message-ID: <9659CE43107944DF8A7F81D69373369E@JimPC>
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
References: <1B3950C0CC6641F29CD92B0269A04581@JimPC> <6CAB0066191C4E76B92C8821061A1CB9@AGB> <20090511101759.CBFC3F3863@smtps02.kuleuven.be>
In-Reply-To: <20090511101759.CBFC3F3863@smtps02.kuleuven.be>
Date: Mon, 11 May 2009 21:59:16 +0100
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Subject: LF: Re: 3 Mode Beacon
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Dear Rik, LF Group,

There are a couple of things I have noticed about MFSK4 receiving Graham's 
beacon, and in a QSO with G0NBD and M0LMH last week:

The frequency has to be set accurately; a 3Hz offset was enough to prevent 
any copy.

The AFC function in FLdigi did not appear to work well in this mode.

Once set to the correct frequency, you have to wait several seconds before 
any copy is produced. This would seem to be because of the interleaving of 
data over several transmitted symbols.

The result is that unless TX and RX frequencies are accurately calibrated, 
it is quite possible to get no copy with good signals. Adjusting the 
frequency offset by trial and error is tricky, especially with short 
transmissions, due to the delay in decoding. Once the frequency is 
accurately set, it seems to work quite well, although it was slower, and had 
wider bandwidth, compared to the other two modes.

I will probably be transmitting WSPR again in the next few days, once the RX 
antennas are sorted out - maybe I will even be able to receive you then ;-) 
I'll let you know.

Cheers, Jim Moritz
73 de M0BMU

----- Original Message ----- 
From: "Rik Strobbe" <rik.strobbe@fys.kuleuven.be>
To: <rsgb_lf_group@blacksheep.org>
Sent: Monday, May 11, 2009 11:17 AM
Subject: Re: LF: Re: 3 Mode Beacon


Jim, Graham,

MFSK4 seems to be good once you have it synchronized, as John (W1TAG) 
states.
But the threshold to synchronize seems to be rather high.
Despite the fact that you signal was audible and
the both Throbx2 and psk31 were printing well I
couldn't decode anything in MFSK4.
MFSK4 is probably a good mode to scope with
QSB/QRN for a signal the that peaks strong enough
but when the signal is really weak Throbx2 seems the winner.
A pity that there is little info about Throb(x) on the web.

73, Rik  ON7YD - OR7T

PS:
Jim, if you plan another WSPR session please let
me know. I will try to join (transmitting).