Message-ID: <004b01c81ed0$d4e46d70$6d3e6a58@wgt01>
From: "Gary - G4WGT" <g4wgt@tiscali.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <00f201c81e39$d10712d0$f7636a58@wgt01> <001701c81e3b$b16e2ab0$0e00000a@AGB> <010d01c81e3d$3528e510$f7636a58@wgt01> <002d01c81e53$32f07f40$7f107ad5@w4o8m9> <019401c81e58$5c428dc0$f7636a58@wgt01> <000a01c81e72$31c8b000$2a298351@w4o8m9>
Date: Sun, 4 Nov 2007 10:52:45 -0000
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Subject: LF: Re: 500 KHz Narrow RTTY
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Good Morning LF,

My thanks to Graham - G0NBD, Jim - M0BMU & Dave - G3WCB for the very 
interesting reports & comments regarding my narrow shift RTTY tests. It 
looks quite likely that this mode could be competition for normal CW QSO's 
at 20 wpm were RTTY 45 Bd gives the equivalent of 60 wpm without taking too 
much bandwidth on a small band allocation ( 23 Hz in this case).

The findings have surprised me in such that I believed that the narrow shift 
could be a problem but as Jim stated with a little care tuning to the signal 
a very good percentage copy can be achieved.

In Jims case the distance is 268 Km & Dave 274 Km.

During the test I was also monitoring Johns (GM4SLV Shetland) grabber IP90GG 
at 739 Km & Daves (G3YXM Birmingham) grabber IO92BK at 143 Km. The traces 
there were such that at Birmingham the qsb periods between dips were short & 
deep but at Shetland the QSB period between dips was much longer & dips 
shallower maintaining a longer readable trace. The traces after dark at 
Shetland were so strong that my RTTY signal was producing a solid white line 
so in those terms we could expect the narrow RTTY would have given a 100% 
copy.

Perhaps John could send me or make available to some captures of last night 
so I can include them on my web site at the next update, even better if 
there were a sound bite available.

Thanks to all for watching & reporting.

73

Gary - G4WGT - IO83qp




----- Original Message ----- 
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: Saturday, November 03, 2007 11:35 PM
Subject: LF: Re: Re: Re: 500 KHz Narrow RTTY


> Dear Gary, LF Group,
>
> The attachment shows a spectrogram of the last hour or so of your test, up
> to around 2251utc - earlier periods were similar. The upper trace is 
> G0MRF's
> beacon, which is quite local to me, and the lower trace is G4WGT. As far 
> as
> readability goes, the transmissions that are fairly yellow were printing 
> out
> with few errors; this was about 20dB above the "blue" noise floor on the
> spectrogram. I would estimate that this mode will work with similar signal
> levels to CW - the "yellow" signals would have been comfortable audible CW
> copy. As you can see, the periods of QSB are quite variable - For a short
> QSO of a couple of minutes, this wouldn't be a problem, but long QSO would
> require standing by waiting for the signal level to build up after a 
> fade -
> also rather like CW.
>
> I used MMTTY for reception - with 23Hz shift, the signal has to be tuned
> quite accurately for best reception, perhaps within 5 Hz, and I found it 
> was
> neccessary to turn the AFC off to avoid it wandering off towards G0MRF's
> CW/PSK31 signal - the separation between the two signal carriers was only
> 100Hz, so not surprising I suppose. The bandwidth of the narrow RTTY looks
> quite similar to PSK31.
>
> Thanks for the test,
>
> Cheers, Jim Moritz
> 73 de M0BMU
>
>