8 FAX
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8.10
Tips and Tricks
8.10.1
IF-SHIFT
With the normal SSB speech reception, the speech frequencies stretch from 300 to 2700
Hz. Steep sided SSB filters usually have a 6 dB bandwidth of around 2.4 kHz. The FM-
FAX standard sets a center frequency of 1900 Hz. With standard resolution FAX and
SSTV pictures, the signal requires a bandwidth of approximately 2.5 kHz. The audio limit
frequencies that should be transmitted are 1900-1250 Hz and 1900+1250 Hz or 750 Hz
and 3150 Hz. The frequency band for FAX/SSTV appears to be shifted about 400 to 500
Hz higher in frequency. With normal SSB reception, the higher FAX/SSTV tones suffer
great attenuation and thereby cause asymmetrical reception.
In order to help this situation, it is recommended that the IF-SHIFT control be used. With
the TS-450 for example, it has been found that the best setting is around
3 o’clock
.