User's Manual

6 1892 1344 - SX450G Transceiver Operator Guide v1.2 / Dec 2006
OVERVIEW OF FREQUENCIES AND PROGRAMMING
Each radio is built to order to cover a band (the switching bandwidth) of 15 or 20MHz
within the range 400 - 490MHz. Available bands are 400-415, 415-430, 430-450, 450-
470, and 470-490MHz. Each radio is also manufactured to work with a particular channel
width of 12.5kHz, 20kHz or 25kHz. These are fixed parameters, and cannot be changed
by the user.
Within the switching bandwidth, the unit can operate on any frequency (provided it is a
whole multiple of the comparison frequency - see page 9), and up to 256 frequencies can
be stored as numbered channels 0 to 255.
There can also be an offset between transmit and receive frequencies, which is the same
for all channels. You can set this offset, but both transmit and receive frequencies must
remain within the switching bandwidth, fixed at manufacture.
During operation, a channel can be selected at any time either using logic lines or a serial
data input. Logic lines can only select channels 0-63, serial commands can select any
channel.
Before the unit leaves the factory, each of 256 channels is allocated to a frequency, but
you can reprogram them if you wish. To do this, you need to read the existing data from
the unit, edit it using a special program supplied by Wood & Douglas (SXWIN.EXE),
which runs on a PC under Windows, then write the data back to the unit.
You can program the unit in one of two ways:
v 256-channel mode: All 256 channels 0-255 can be programmed, but as a
block by entering a starting frequency and a step size, so that they contain
uniformly spaced frequencies.
v 80-channel mode: Each of channels 0-79 can be individually programmed
with any frequency, but the remaining channels 80-255 are not available for
use.
One channel is then nominated as the operational channel.