Without military or government communications experience, the assignment
of frequency by center of the channel is foreign to amateur radio. What
these mean is that we will be running SSB with the carrier frequency 1.4
or 1.5 KHz below the assigned channel center frequency. Though with the
carrier offset 300 Hz from the filter edge, perhaps we could run one SSB
signal with the carrier 1.7 KHz below the center frequency and another
(using a 1.8 KHz transmit filter) with the carrier frequency 2.1 KHz
below the top, or 700 Hz below the center frequency. They'd overlap, but
no worse than evenings on 75 meters with suppressed carriers 1 KHz
apart. Still keeping the total bandwidth in use to just 2.8 KHz.
When frequency assignment by center of channel was introduced to MARS 20
years or so ago, some stations and state directors had a hard time
figuring out where they should transmit, either voice or RTTY with AFSK
tones.
73, Jerry, K0CQ
--
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.
|