Jim,
Thanks for your comments.
Your comment about out-of-band levels is correct. Ofcom's key concern in
agreeing to raising our ERP level is that of the effect outside 501 -
504kHz; the reason that the upper limit is 504kHz is to provide a guard-band
between our usage and 505 - 510kHz and 505 - 525kHz allocations.
My feeling is that Ofcom want to be able to satisfy MCA that their use,
irrespective of actual systems, of the spectrum around 501 - 505KHz would
not be put at risk from Amateur usage at the higher power. To make our case
for Agenda Item 1.23 at WRC11 we will of course need to do some technical
studies that will include looking at protection ratios with primary user
services. We've already done some preliminary work on known systems, such
as NAVTEX and NDBs, which look promising. I don't think that Ofcom want to
get into this detail with MCA at present. The other reason for the
bandwidth issue could be because of footnote 5.82A in the Radio Regulations
- "The use of the band 495 - 505kHz is limited to radiotelegraphy". This
footnote was inserted in the Radio Regs at WRC07. If Ofcom can say that we
are restricted to 200Hz bandwidth or thereabouts and leave it up to us what
actual modes are used they perhaps feel that they are keeping roughly to the
spirit of 5.82A in terms of spectrum occupancy. It would obviously be in
our interests to have flexibility to investigate novel modes.
I agree though that novel modulation modes to overcome these fades will
probably need wider, rather than narrower, bandwidths if we are to keep the
information rates reasonable. It's more likely though that such innovation
will have to wait until we get a reasonable slice of spectrum after WRC11 -
it must be the Christmas spirit making me so optimistic!
73 John, G3WKL
_______
|
