[Premium-Rx] Fw: Plessey PRS-2282A

[Michael O'Beirne]

----- Original Message ----- 
From: "Michael O'Beirne" <michaelob666 at ntlworld.com>
To: <GandalfG8 at aol.com>
Sent: Saturday, July 10, 2010 6:42 PM
Subject: Re: [Premium-Rx] Plessey PRS-2282A


>
> Good evening guys.
>
> I have a 2280 in almost immaculate order.  It spent much of its life in a 
> safe at Plessey as a development mule.
>
> A word of warning for those who have the PR2280.  A number of the ICs are 
> special Plessey Semiconductor devices.  With that company long ago 
> deceased, getting spares can be well difficult or impossible since most if 
> the manufacturing masks were chucked out during the corporate carve up 
> between Siemens and GEC.
>
> You will also need the rare PCB extender board if you are going to work on 
> it.
>
> A further issue for those who have the rare half-octave preselector is 
> that Plessey failed to apply a DC wetting current to the relays with the 
> result that they sometimes go hi high resistance despite being excellent 
> American products from Clare Relays.  The high packing density of the PCB 
> does not assist either.
>
> Once all is in order, the recovered audio is excellent, though the tuning 
> is rather rubbery in effect - probably because of the very long PLL lock 
> up time to try to mimimise phase noise from the synthesiser.  However 
> there is instant tune when using the keyboard.  Why there should be the 
> difference I do not know.
>
> BTW the CIO for the product detector can be phase locked to an incoming 
> carrier, and this means that tuning an AM station as SSB produces perfect 
> tuning even if there is drift in the system.
>
> Sadly not many 2280 seem to have been made.  According to my Plessey spy 
> the RAF took a variant with a synthesised BFO and the other major buyer 
> was the China News Agency.
>
> Hope this helps a bit.
>
> 73s
> Michael
> G8MOB