[Premium-Rx] RACAL DK-43 Tuniing Aid

[Michael O'Beirne]

Dear Andy

I have two of these tuning aids in almost mint condition, but no info and 
anything you may discover would be very welcome please.

They were not actually made by Racal but (so I am told) by Tewkesbury 
Electronics, Gloucestershire, which is just up the road from Cheltenham 
where you know who lives, and that this firm undertook various projects for 
that organisation.

The DK43 gives a more linear display at the edges than Racal's similar 
bargraph, the MA1105.  However, unlike the MA1105, the DK43 accepts an input 
of only 100kHz (the 1105 can be switched to 1400kHz, and there is a rare 
455kHz version, the MA1105B).

The trouble is that with my RA17L, the DK43 tunes backwards, ie as you 
increase the frequency the lights move backwards, unlike with the MA1105. 
It may perhaps tune with the right sense with the RA117 and similar radios 
since they have an extra conversion stage which reverses the sideband sense. 
However it is not a major problem.  It enables me to tune a CW, AM or FSK 
station to within 20Hz without reference to the receiver's film scale.  Not 
bad for a 50 year old radio!!  But they don't do anything useful for a 
signal without a carrier!

BTW you may or may not know that GCHQ specified that all receivers for them 
had to have an IF output at 100kHz and that the sideband sense at the IF 
output had to match that at the aerial input.  Thus several of their 
receivers which did not have a standard 100kHz IF output (eg it would 
normally be at 1.4MHz or 455kHz) had to have one fitted internally for them, 
typically the RA1792 and the Plessey PR2280.  I have a copy of the complete 
spec put out by GCHQ and the detailed engineering sales "pitch" from Plessey 
for the PR2280.  The RA3701 series also has an optional module to convert 
the 1.4MHz IF output to 100kHz.

73s and Happy Christmas
Michael
G8MOB


----- Original Message ----- 
From: "acyg" <acyg at btconnect.com>
To: <premium-rx at mailman.qth.net>
Sent: Friday, December 25, 2009 11:51 AM
Subject: [Premium-Rx] RACAL DK-43 Tuniing Aid


> Hello to all,
>
> I have recently acquired a Racal DK-43 tuning aid.
> A very nice item which works perfectly with any receiver with a 100KHz IF
> output.
>
> However being the inquisitive type that I am, I've been searching for a
> manual and circuit diagrams for this unit, but to no avail.
> Can anyone help in any way at all?
>
> May I wish all a very Merry Christmas and Prosperous New Year...
> With many premium receivers for the future.
>
> Andy - G7JQL
> acyg at btconnect dot com