[Premium-Rx] Racal IF Converter question

[Dan Rae]

Thomas Adams wrote:
> */
> I can't find a schematic or specs of any sort on the MS-561/2, and 
> there's no mention of it in the RA-1772 manuals.
>
> Are the two converter channels of the MS-561/2 identical, so that the 
> box can be used for diversity setups without any
> changes?
>
> /*

It's in some of the manuals Tom, because I have seen it.  Maybe in the 
1778 book then, or on one of the appendices.    The 561 exists in two 
versions, one for the single IF the other for two for the ISB optioned 
receivers.  I see no reason why it would not work for two diversity 
receivers, but that was not the original idea obviously; they intended 
diversity to be done with the audio switching unit for RTTY and cw / 
ssb, that is how it is shown in the manual, and I don't see how using 
the elderly RA1217 / 17 era MA168 would improve on that...  Both the 
MA561s I have are single IF versions.

The conversion is done with 1500 kHz injection, from memory by tripling 
the 1 MHz and then dividing by two.  The ISB version has two cards in 
it, the single IF version has just the one.  Since the injection is 
locked to the 1 MHz output from the (master) receiver, assuming you 
slave the second receiver to that as well, it should work for diversity.

I'm not sure what the main intended purpose of the MA561 was.  Almost 
all of the Racal Receivers from the RA1217 on had an option for a 100 
kHz output, possible for compatibility with RA17 era ancillaries, and 
indeed it is very useful to have it for frequency measurement and signal 
analysis.  All my RA1792s have it fitted. Similarly the US versions  
with 1.4 MHz IFs often had a converter to 455 kHz  as an option, both  
my 6772E and 6778 have them,  presumably also to use outboard equipment 
left over from earlier receivers.   But again diversity was done 
otherwise as a rule.

Cheers,

Dan
ac6ao / g3ncr