[Racal] Help on Racal filters

[Howard L Ritter, Jr]

Well, fools rush in and all that....

I took the top cover off my new 6790 and what did I find but another cover I
could take off. I took it off and what did I find but 5 filter assembly cans
that I could gently pull out of the circuit. So I did (because I could, I
guess--don't tell me you've never done the same!). I thought I was paying
close attention to which socket each came out of, but when I put them back
in, a couple of things happened that I don't understand. (The filters are
0.4, 1.2, 3.2, 6.8, and 16 kHz.)

Before I diddled around, the filters were not physically in the same
positional order as selected by the "BW*" keys on the control panel, nor
were the filters all adjacent; four were, but one was spaced two slots away
from the rest and out of order (I think the slots used were 16 kHz in slot
2, 6.8 in 3, 1.2 in 4, 0.4 in 5, and 3.2 in 7). In AM, the bandwidths
selected by the BW keys and indicated on the display corresponded to the
values given on the filters, and the audio was consistent with the correct
order of the filters. In USB/LSB the filter defaulted to what sounded like
3.2 kHz and was not changeable by pushing any of the BW keys.

After I put everything back where (I think!) it came from, the bandwidth
readout on the display is correct for the 0.4 kHz filter, but the others now
read 1.5, 3.3, 8.1, and 19 kHz. The audio quality indicates the correct
ordering of the filters in AM, so it would seem that I have everything where
it should be. However, in USB or LSB a very narrow filter is now selected
and the audio unintelligible. I have run BITE and nothing has changed.
Playing with the positions of the filters, in the best tradition of and all
that, produces no correction of the anomalies. Maybe I need to run BITE
after each repositioning of the filters?

Anyone have any idea what's going on? Is there a software command that will
get me back to the right filter for sideband? What's with the anomalous
display of bandwidths? Does BITE do more than just test the receiver, i.e.,
also tell the controlling firmware how the receiver is confingured?

Still haven't sprung for that manual....

Thanks in advance,

--howard nexn