Those of us who have been around RTTY before the days of electronic
printers remember the second meaning of LSMFT - low space means fine
teletype. (refers to the RF frequency, not the demodulated audio of course.)
Jack K8ZOA
www.cliftonlaboratories.com
Joe Subich, W4TV wrote:
RTTY was based upon the frequency
of Mark (2125) and Space (2295) and the surplus military
equipment available, unless you could afford some of the high
dollar HAL equipment (which was also used by the military).
No, RTTY is always "Shift low" - that is Mark is the HIGHER
RF frequency and space is the LOWER RF frequency. When the
audio tones 2215 and 2295 are applied to a LSB transmitter
in AFSK this results in the correct shift.
I have no idea what the protocol is for DATA (perhaps Elecraft
can tell us.) As an experiment, try switching rigs in MixW and
observe what is happening to the signal frequency.
FSK D and AFSK A receive in LSB while PSK D and DATA A receive in
USB for compatibility with the (backward) convention of most non-
RTTY software writers (PSK32, MFSK, etc.).
73,
... Joe, W4TV
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Rich (KE0X)
Sent: Friday, June 27, 2008 4:49 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] K3 Firmware 2.10,1.81 problems Update
As Julian suggested the problem is in MixW. It has been 40
years since I had the RTTY training course in the NAVY, but,
it has to do with the convoluted history of RTTY. Although
SSB is on the LSB on the HF bands below 30 Meters and USB on
those bands above 30 meters (Many reasons given for this most
of which are not correct) RTTY was based upon the frequency
of Mark (2125) and Space (2295) and the surplus military
equipment available, unless you could afford some of the high
dollar HAL equipment (which was also used by the military).
Military protocol was to have the Mark the lowest tone in
frequency. This was ok with most equipment made BPC (Before
Personnel Computers). The PC brought out the conversion of
telephone modems, use of the modem IC’s and finally the PC
sound card for generating these tones. If you built a TNC out
of a modem chip and did not include a reverse switch you were
stuck to either the low or high bands. This was fixed on the
PC with a button to reverse the signal that you could click
on and copying. Some of the Rigs treat RTTY as SSB, others
put RTTY so that the Mark is always the lowest frequency
transmitted regardless of the band selected, and RTTYR
reverses this. I have no idea what the protocol is for DATA
(perhaps Elecraft can tell us.) As an experiment, try
switching rigs in MixW and observe what is happening to the
signal frequency. You wil not be able to chang frequency
with MixW but you can see what happens to the signal as you
turn the dial on the RIG.
Rich,
KE0X
--
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