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RTTY
Frequency Guidelines
Following
regular
complaints of RTTY stations encroaching on the PSK sub-band, HFCC
members were monitoring the May Data leg.
A number of problems were identified, the most significant being that
some RTTY operators were relying on their rig's frequency display to
indicate their
radiated frequency. These displays may require considerable
interpretation before they indicate correctly.
Consider a station with a
transceiver set up for LSB and using a
software package such as MMTTY. The software injects tones of (by
convention)
2125 and 2295Hz into the microphone socket to produce an LSB FSK
transmission. The rig's frequency display reads 3584.0kHz (outside the
PSK sub-band)
but the actual frequencies radiated are 3581.705kHz and 3581.875kHz ,
(3584kHz -2295 and 2125 Hz) both within the PSK sub-band.
Using a rig which generates FSK directly can give different results
again, often dependent upon the rig's menu settings.
Stations transmitting RTTY need to be certain that they KNOW, whether
by calculation or direct measurement, EXACTLY what frequencies they are
radiating.
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