On 6 Jul 2003 01:10:01 -0700, Brian Kelly wrote:

have no idea how or why the BC stations choose their specific
operating freqs within their bands. Gotta be strategies involved. Any
clues here?

Four times a year, the ITU International Frequency Registration
Board (or whatever it's called nowadays) holds a conference for SW
broadcast frequency assignment. Most of it is by paper submission
and is routine "we've been on this frequency for 70 years....."
stuff.

For new requests, the requesting Administration will have submitted
info on the location of the transmitter, directionality and power,
hours of service, and the target area. A computerized frequency
coordination study is made by the IFRB to determine what frequency
in the band in question would cause no harmful interference to
existing (earlier priority date) stations. Quite often the
coordination will be for less or different hours or power than
requested to avoid any harmful interference to or from the
applicant. This coordination will be "ratified" at the quarterly
conference and a priority date assigned.

One thing I do know is that significant freq shifts can cost the BC
stations a bunch of money because the equipment and antenna arrays are
purpose-built & tweaked for operating on specific freqs. I understand
that they cannot just grab a big knob and twist it to QSY 150 kHz like
we can. I 'spose this is why it'll take six years to fully implement
their move out of 7.0-7.1.

Or so they say. A 150 kHz shift is no big deal as long as the
broadcaster is willing to take the transmitter down for a period of
time (weeks? months?) to find the proper coil and capacitor settings
(synthesizers are a no-brainer nowadays). A good friend of mine was
a tech at a SWBC station years ago and could do a band change with
pre-set taps in less than two minutes (of course the walk-in 50 KW GE
monster was shut off during that time).

The long lead time comes in not where the broadcaster has to
order and install parallel equipment currently (from scratch it
should take no more than 2 years at the very outside) but where the
broadcaster wants to amortize the equipment, i.e. when they are
ready to order a new transmitter they will order it for the new
frequency.

--
73 de K2ASP - Phil Kane