QRM-free Digital SSTV.
Digital SSTV users
growing day by day and like in old days for SSTV we have to find
a way to operate hopefully in a QRM FREE environment. 14240 kHz
is often in EU used as CQ point for Digital SSTV, stations gather here and we have an inferno of
transmitting -1750 tones-Tunings-WF messages-Callsigns-Files- but
no listening or use of microphone and not a single complete
contact can be done.
This situation is just like that for
analog SSTV at the end of the 1980´s. SSTV segment of 10 kHz was
too narrow (read above in "Operate QRM-free SSTV"). I
asked the Swedish Amateur Radio Society for help and in 1992 we
introduced a bill to the IARU Region 1 asking "How to
improve the conditions for HF SSTV? Region 1 Vienna meeting in
1995 gave the following answer (HF/Doc.93/DHB/C4.15):
"It is recommended
that the frequencies 14.230; 21.340 and 28.680 MHz should be as
calling frequency for SSTV/FAX operators. After having
established contact, the station should move to another free
frequency within the telephony portion on the band"
If we now imitate the above rule for
14240 (some similar spot on the 21 and 10 MHz bands) we find a
way to have QRM FREE contacts also in Digital SSTV but we have to adopt some simple operating
rules like:
- Listen carefully and identify
yourself and ask by VOICE if 14240 is free. If the spot
is free, call CQ by VOICE and send your TUNE signal.
- Station(s) reading
you answer you by VOICE or sending CALLSIGN. By VOICE ask
your answering friend(s) to follow you to a clear spot
(up or down in 3 kHz steps) on the band.
- A breaker should not break into an
ongoing QSO to call attention. Break in by VOICE (break)
between transmissions. Trained operator wait always some
seconds before starts to transmit again.
- If 14240 not free, follow the same
procedure for CQ in 3 kHz STEPS up or down (1 - 2 kHz is
too narrow).
- Spread out Digital SSTV activity on our bands.
- Remember use
MICROPHONE and before you transmit anything use TUNE
signal.
- Porno pictures are banned,
Children, YL´s and XYL´s watching also the screens.
Back to Home