[Collins] 51J-5

[Dr. Gerald N. Johnson]

How early, the 51J scheme came out in the 1950s well before the 1959 
introduction of the S-line? The AR8516L manual I've found on line 
appears to date from May 1969 though I continue to search. I've believed 
the concept of tunable IF with crystal converters was a Collins 
innovation beginning with the 75A1 that achieved frequency readout 
precision and stability far better than that of the competition that 
bandswitched the HF tunable local oscillator, like the Super Pro and the 
AR88.

Reading deeper into the AR8516L manual I find that the LO injection is 
always the IF above the tuning range like the 51J. Where the 51J 
interchanges sidebands is that its MF PTO tunes only 1 MHz but two 
tunable IF ranges are used, one above the PTO and one below the PTO. So 
each crystal works for two 1 MHz bands, though for higher bands 
harmonics of lower frequency crystals are used to minimize the crystal 
count.

I see that the AR8516L manual doesn't appear to define which side band 
you get by which off set direction you give the BFO, just that if you 
can't copy a SSB signal, try the other offset direction.

I'm always interested in good receiver designs, I'd not know of the 
AR8516L before.

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.

On 4/17/2010 2:56 AM, G3OOU at aol.com wrote:
>
> <SNIP>
> I believe that a similar frequency conversion technique was used by RCA in
> the earlier AR8516L receiver - I have only ever seen one of these in the UK
> and  that was many many years ago.
>
> 73
>
> Bob
>
> Bob F Burns
> Amateur  Radio Callsign: G3OOU
> G-QRP Member No: 6907; QRA: IO91WH; WAB: TQ25
> Joint  web site with Crystal Palace Radio&  Electronics Club:
> _www.g3oou.co.uk_ (http://www.g3oou.co.uk/)
> Technical web site: _www.qsl.net/g3oou _ (http://www.qsl.net/g3oou)
> ______________________________________________________________
>