[Racal] Re. What have I done?

[Thomas A. Adams]

Hello Howard.

I know what you're saying in that message title.

I've been infected by the Racal bug for only about a month now, but I
find myself the owner of THREE RA-6790/GMs, plus an RA-6793, and
I'm currently awaiting the delivery from England of an RA-1772!!!

I fell into a lucky deal on Racals; Gawd help me when I get hooked on
Watkins - Johnson...

Congratulations are definitely in order; you've graduated from the toys
and "busy boxes" full of neat bells & whistles that they produce for the =

ham / SWL market, and found out about the understated technical
elegance of professional communications receivers.

As far as I know, the green LED display illumination is the last version
produced. Never heard of a "white" LED; are you referring to the older
version that uses incandescent bulbs?

As for the receivers themselves... I've already gotten a practical lesson=

in servicing the RA-6790/GM. While these ARE complex rigs, they're =

not too bad to work on (I got a fault indication of unlocked PLL on the
2nd conversion osc / BFO). =


The only advice I can offer there is two points...

1- UNDERSTAND TTL IC CIRCUIT THEORY BEFORE YOU DIG IN!!!
And that means have a decent scope available to watch what's going =

on...  I'd say 50 MHz or faster, and dual trace is useful. Trigger offset=
 /
delay is also a handy feature to have.

2- Don't count on the commonly available manual (TM RA6790/GM-3)
to be much help. The military these days thinks of "servicing" as a game
of replacing whole subassemblies...  not a viable option for "real world"=

(ie, non-DoD warehouse supplied) users. =


The most useful thing I found there was the schematics. With those,
plus a bit of common sense and a dose of intuition about how the TTL
logic is SUPPOSED to function, I got thru the crisis here. =


Did you get the LF frequency extension package in your rig? I did, and
it's excellent! :o)

73's,

Tom, W9LBB
Sun Prairie, WI