> In fact I have tried up to 110 Baud. Using 170Hz shift within
> a 250Hz filter width errors start creeping in at 110 Bauds and
> even at 100 Bauds, but 75 seems a good standard to aim for.
If your filter is truly 250 Hz at -6dB, it is too narrow for
even 45.45 baud 170 Hz shift RTTY as the required bandwidth
is roughly 270 Hz. Most "250 Hz" filters are actually wider
- often between 300 and 350 Hz which results in an effective
bandwidth of 250 Hz when cascaded with a 280 - 300 Hz wide
filter at 455 KHz (e.g., INRAD #186 or #704).
The required bandwidth for 75 baud/170 Hz shift RTTY is about
350 Hz. 100 baud represents about 420 Hz and 110 baud gets
to about 450 baud although the onset of bandwidth issues may
be masked by QRM, QRN, multipath and selective fading.
> It would increase Q rate in both contests and DX-pedition
> pile-ups, but it certainly is stressful on the typing!
I have to question the wisdom of higher speeds. Even with
short "canned" messages like those in contests or DXpeditions
the overall data rate increase is not anywhere near the raw
difference in data rate considering transmit to receive and
receiver recovery times. The time "advantage" disappears
completely for keyboard RTTY (or paddle generated RTTY from
an Elecraft K3).
It seems to me that the pursuit of higher speed RTTY is
speed for speed's sake without consideration of the extra
bandwidth (QRM) or compatibility with existing hardware
(e.g., Icom's "twin peak" filter, or the Elecraft paddle
generated RTTY) problems inherent at the higher speeds.
73,
... Joe, W4TV
> -----Original Message-----
> From: rtty-bounces@contesting.com
> [mailto:rtty-bounces@contesting.com] On Behalf Of Roger Cooke
> Sent: Thursday, January 28, 2010 5:26 PM
> To: rtty contesting rttycontesting
> Cc: bartg@bartg.org.uk
> Subject: [RTTY] High Speed RTTY again
>
>
> Hi.
>
> Judging by the amount of emails flying about there does seem
> to be some
> interest in 75 Baud RTTY at last! I have had several QSOs
> at that speed
> both on 80 metres and 20 metres with total success. In fact I
> have tried up to 110 Baud. Using 170Hz shift within a 250Hz
> filter width errors start creeping in at 110 Bauds and even
> at 100 Bauds, but 75 seems a good standard to aim for. It
> would increase Q rate in both contests and
> DX-pedition
> pile-ups, but it certainly is stressful on the typing!
> I usually answer points as the other station is transmitting anyway
> and then
> sending at full speed it sure does rattle along. I will be
> calling CQ
> on 20 metres
> on Friday at around 1400z at 75 Bauds if anybody wants a QSO.
>
> John, GW4SKA certainly is giving it some thought now for a
> BARTG contest at that speed, possibly a short one, but as he
> says, although membership of BARTG is free and we would like
> as many as we can get, staging the contests does cost, with
> the certificates and plaques and things. Small donations
> add up
> so please consider making just a token donation when joining. It will
> all help
> sponsor the contests, plus BARTG also sponsors DX-peditions
> too. If you would like to sponsor a plaque too, that would be
> really nice! Perhaps all RTTY contests will move over to 75
> Bauds. :-)
>
> The next main BARTG contest is the Spring, in March. Don't
> forget the GB50ATG event that is on-going too. There are some
> nice certificates and plaques available for that. GB50ATG
> finishes at the end of July. Take a look on the BARTG web
> site, and see if it floats your boat, cocas your cola,
> bakes
> your cake, or diddles your Baud!!!
>
> www.bartg.org.uk
>
> Send some feedback. Hey, if you DO join, why not send us
> some pictures
> of your station/antennas etc., for the Gallery. You can
> even see the
> mug-shots
> of the committee on there if you can stand it!
>
> See you on the green keys on 75 Bauds Fri PM.
>
> 73 de Roger, G3LDI, Chairman, BARTG
> _______________________________________________
> RTTY mailing list
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