[Premium-Rx] RA1772 and 1778 manufacturing dates

[Michael O'Beirne]

----- Original Message ----- 
From: "Michael O'Beirne" <michaelob666 at ntlworld.com>
To: "John Nelson" <john at crew-green.com>
Sent: Sunday, February 10, 2008 12:42 PM
Subject: Re: RA1772 and 1778 manufacturing dates


> Dear John
>
> The earliest public reference that I can find to the RA1772 is Roger 
> Winn's celebrated article "Synthesised communications receiver" in 
> Wireless World of October 1994, describing the design considerations for a 
> wideband receiver and, specifically, the RA1772.
>
> My glossy RA1772 brochure is copyright dated 1976.
>
> Are you aware of the earlier RA1770, using an RA17 type of film scale 
> rather than LEDs?   I attach separately an extract from Short Wave 
> Magazine, volume XXIX.  There is no date and I don't have that issue, but 
> you can work backwards from volume XXXII (which I do have), which covers 
> March 1974 to February 1975.  That would suggest that the XXIX volume 
> covered March 1971 to February 1972.  The page number is 757, and from 
> later volumes that indicates about February - hence about Feb 1972.  I 
> think I copied this page at the old Patent Office Library off Chancery 
> Lane in about 1980.
>
> The 1772 used the Rafuse switching mixer which, I think, had first been 
> published in about 1970, and so an initial design reaching prototype 
> status in about 1972 is not unreasonable.
>
> If you look at the 1772 block diagram, you will see that there is a 
> synthesised VFO covering 3.6 - 4.6MHz.  It may be coincidence that the VFO 
> in the valved RA117 tunes this range as well, or perhaps not.
>
> I have seen no reviews or descriptions of the RA1778 or 1779 in 
> professional journals.  The copyright date on my glossy brochure for the 
> RA1779 is 1978. My guess is that the manufacturing start date for the 1778 
> is around 1976.
>
> Do you know whether there was an RA1773, 1774, 1775, 1776 and 1777?  I 
> think that the 1774 was the maritime version with a narrower 2.35 kHz USB 
> filter in place of the normal 2.75 kHz filter in compliance with the SOLAS 
> Regs, but I have never seen any.
>
> BTW the 1770 series came in a large number of different filter fits 
> depending on the intended use and customer.  My paperwork here reveals 47 
> different fits and there may be more.
>
> 73s
> Michael
> G8MOB
>