[Premium-Rx] PRESELECTORS

[Danny Higgins]

Don't forget the Racal MA1101 remote tuned HF preselector and the MA1120 
manual version of it.  The MA1101 would measure the Local Oscillator of 
the receiver and tune itself accordingly.  It could cope with either 
35.4MHz IF (RA177x, RA178x) or 40.455MHz (RA1792).  It was motor tuned 
very quickly using beefy stepper motors.  It was intended for high RF 
situations or to limit broadband noise from an HF drive unit before the 
TX amplifier.

It was designed to withstand 200V of RF.  Someone at Racal worked out 
that this was 800W into 50 Ohms, so they fired a 1kW HF transmitter into 
the MA1101 to test it, and forgot about a 10 kOhm resistor on the front 
end which was used to "wet" the relay contacts.  The result was a badly 
charred board.

Danny, G3XVR

GandalfG8 at aol.com wrote:
> In a message dated 30/11/2007 22:53:02 GMT Standard Time,  
> Mikewhiskyone at aol.com writes:
>
> Just my 10 cents worth, the VIGILANT MICON SR532 has a  rather elegant  
> motor driven preselector as per Eddy1650  Racal 1772( Same   board used I 
> believe 
> on the optional preselector unit for the 1792) etc,  and my  observations of 
> the Vigilant one is that its really good, my  last QTH was  literally yards 
> from 
> a pager TX, which should have been  dealt with by the high  pass filter in 
> the 
> receiver, but was not, and  the Vigilant preselector did the  job of 
> rejecting 
> it, in fact, the  only PREMIUM-RXs here that were FULLY  able to deal with 
> the 
> pager  were the SIEMENS CHR531, now sold, the SR532,  and the RF-590A, both  
> now up for sale, as I am no longer at that location, Dave   MW1DUJ.
> ---------------------------------
>
>
> Hi Dave
>  
> I didn't realise the Vigilant had a motorised preselector, but that's  
> probably because my efforts to snare one via the usual hunting ground has so far  
> proved unsuccessful:-)
> There is quite a nice looking 590A on offer right now, but that's also much  
> too expensive for me:-)
>  
> Seriously though, that does give me another reason to keep looking out for  
> the Vigilant.
> What Michael didn't mention was that there are still quite a few  sets 
> available, usually marine kit, with very nice manually tuned  preselectors.
> Sailor and ITT Mackay are just two commercial receiver manufacturers  that 
> come to mind, and even Kenwood did a pretty god job with the  R820.
>  
> Collins also did a nice job with the HF8060 but that does need some  
> interfacing if not used with the appropriate Collins kit as it's bus controlled  only.
> Unfortunately though, as Gary pointed out earlier for the Harris  kit, this 
> is another one intended for HF use only.
>  
> regards
>  
> Nigel
> GM8PZR
>
>
>
>    
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