[R-390] OT: Other Radios You Like

[2002tii]

Cecil wrote:

>I haven't heard anyone mention much about the Racal 6790/GM.  I have 
>always wanted to play with one of those in top notch 
>shape.  Probably nothing special but just one more on my list.

As a band-scanner, the R6790/GM stinks.  The three tuning rates on a 
normal R6790/GM (R-2174 and R-2174A) are (1) way, way too slow, (2) 
too slow, and (3) way, way too fast.  The membrane keys are hideous, 
the ergonomic pits -- it feels like a $35 microwave oven.  But the 
radio works just fine.  As far as I know, the R6793/GM is essentially 
the same thing with keyboard-type switches, memories, and scanning 
capability.  I also think the British Racal 6172 uses the same 
modules.  One feature of these radios is very cool -- you can put 
filters in more or less any position, and the self-test will 
determine the bandwidths and exact center frequencies and program the 
oscillators to center signals in the passbands.

One thing I found -- they didn't put diode switching at both ends of 
the IF filters, so all the filters are fed in parallel and you select 
the output you want.  It works OK, but the leakage from the 16 KHz 
filter spoils the skirts of the other filters.  All of the other 
filters work much better if you remove the 16 kHz filter.

I have the LF/VLF/ELF version (the R-2174B(P)/URR) -- it will tune 
right down to 1 kHz.  I haven't entirely figured out its conversion 
scheme -- it has more conversions than a standard R6790/GM, and I 
have yet to find a manual.  Supposedly, only 200 were made for the Air Force.

If anyone knows where I can find a manual for this beast, I'd be very 
interested in knowing.  In addition to the usual complement of 
R6790/GM modules, the LF/VLF/ELF model has additional modules A14, 
A15, A23, A24, and A25.

Best regards,

Don