From Dave G3YMC
Bandplans are an attempt to all users of a band to operate in harmony without
causing
each other interference. I would hope you would see these comments in that
light!
For instance, on the hf bands it is difficult to have a CW QSO underneath an
SSB one
(although some SSB ops seem quite happy to chat on totally oblivious to the CW
QSO
beneath them (happens all the time on Top Band..). Hence the historic division
of
the bands into CW and SSB segments. Although in the bandplans CW is allowed
anywhere
in the band (to allow dual mode QSOs), in practice all CW activity is confined
to the
CW only parts. The original CW segments have narrowed over the years to
accomodate
the incoming digital modes. Incidently the announcement of a data beacon on
1843
(admittedly low power) raised consternation in Top Band qrp ops - 'why do they
always
choose the QRP frequencies?'.
136 is of course an unusual case, primarily because of its narrow band.
Rightly or
wrongly therefore it has been decided that a hard and fast bandplan is not to be
made. However the requirement to make it available to all users and
(narrowband)
modes remains, and it is on that basis that it has been drawn up and submitted.
The biggest problem the CW users face on 136 is receiver bandwidth. Many of
us, and
certainly the casual listener we are trying to encourage to get interested in
the
band, will have a 350Hz (or even wider) CW filter with not particularly sharp
skirts.
Some operators have narrower CW filters and/or dsp filtering in their receivers
- but
probably none of them have anything better than 50Hz with square edges!
With a simple split, CW in the lower section and other modes in the upper
section,
this is not a problem - though clearly more bandwidth is required to fit the
same
number of CW stations than their narrowband counterparts. In general that split
works well, and with the Ropex around 136.55 has led to the current CW usage
area.
However with typical receive filters the presence of strong QRSS stations at
135.922
ish limits the usable bandwidth, and if CFH is on on 137.0 there is a relatively
small segment in between that can be used. I am prepared to accept the need to
use
the lower segment for QRSS, but would be disappointed if activity moved any
higher -
in fact when SXV is off (as it seems to be most of the time at present, but
that may
change) there would be a case of moving back down.
I would suggest also that the bandplan data mode segment (137.4-137.6 as it was
in
the original bandplan) is virtually unused. Surely that could be put into use
(although presumably not for transatlantic - but there again CFH is not on much
these
days). With most of these new modes requiring less than 1Hz of bandwidth (even
the
seven dot measle stuff) there is plenty of room there.
Activity is perhaps not as low as some would suggest. Among stations heard
yesterday
(a weekday) included F6BWO, DF3FDO, OH1TN - Reino called CQ several times,
failed to
hear me calling (understandable!) then went away. Last year he would have had a
pileup. Also heard F6BWO on QRSS on 137.1.....
73s Dave G3YMC
[email protected]
[email protected]
http://www.dsergeant.btinternet.co.uk
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