[Milsurplus] RTA-1B ftequency question

[Jack Antonio]

Happy New Year to all.

I'm starting to get a Bendix RTA-1B going, and
have a frequency question.

It looks like the radio was recrystalled around the
beginning of 1954, one of the changes was 3105 became
3023.5. I base the date on a "9-53" marking on one
of the crystal units.

However, two of the channels are in what in
the US is a ham band, 3855 transmit and receive,
and the other is transmit on 7248.5, but the receive
frequency is split, at 7475.5. Theze are not
ham mods, the crystal units were manufactured and
factory marked with these channels. (And
yes, these are actual channel frequencies, the
actual receive crystal frequencies are 455 lower,
3400 and 7020.5).

I'm thinking that 75 meters wasn't provided to
give the pilots something to do on a long flight,
but where were these channels used in aeronautical
service?

And, anyone know what the story is behind the
split channel?  That is pretty common in maritime
service, but what use in the aeronautical service?

Thanks

Jack Antonio WA7DIA
scr287 at sbcglobal.net