Message-ID: <3617AC3245C2D1118A840000F805359C01AB8C4A@pdw-mercury-1.dera.gov.uk>
From: "Talbot Andrew" <ACTALBOT@dera.gov.uk>
To: rsgb_lf_group@blacksheep.org
Subject: LF: Re: LF receivers
Date: Thu, 18 May 2000 12:42:07 +0100
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I use a Racal RA1792.  Gradually becoming available on the surplus
market now, at prices coming down from 'silly'.  They started at Ł1000 a
few years ago but are now appearing at Ł400- Ł500 and ought to drop
further as G_HQ and the coastal radio stations get rid of their huge
stocks.   Designed in the late 1970's and used throughout the 80's,
biggest users were military / government organisations, and commercial
ones such as marine coastal radio stations.

An excellent HF receiver with frequency coverage from sub-10kHz to 30
MHz,  IF filters down to 300Hz as standard, and the essential separate
BFO control for setting the CW tone as well as SSB modes - plus AM and
FM.   Tuning is by knob or keypad entry, and 100 memories are available
which store the complete receiver settings of filter bandwidth, BFO
setting as well as the frequency.  Short and long-hang AGC is selectable
with manual backoff, plus fully manual control over 90dB range with a
single knob.  AGC voltage is available on a rear connector, which could
be used for example for logging purposes.  Rear panel line level outputs
at 1mW are perfect for feeding directly into Soundcards or DSP systems
with a  600 ohm terminating resistor.  The second IF, where most of the
filtering is done, is at 455kHz and an external output is usually
available at this frequency for external processing.  Circuits etc. are
well documented (at least if you get the proper Racal manual), with
large size conventional leaded component PCBs, ideal for 'amateur'
modifications.   

Most importantly for my purposes, all internal frequencies are generated
from the one reference oscillator, which can be fed in externally at 1,
5 or 10 MHz.

The main downside is 10Hz tuning steps, although I believe later models
do allow 1Hz steps.   Another it its weight - about 20kg - and the fact
that remote control (if available) uses a non standard serial data
format even worse than the many amateur rig standards.

...............................

For a really top flight receiver (for lottery winners perhaps ?),
consider the Watkins Johnson WJ8711.  This is a modern digital receiver
for near DC to 30MHz, with just about every filtering function ever
wanted available;  66 IF bandwidths from 56Hz to 16kHz plus other DSP
functions.  The receiver is ridiculously priced in the UK, and is
subject to US export controls (it is considered to be a Munition,
believe it or not !! ) but Lowe do (did ?) sell a 'commercial' re-badged
version, which as far as I can see is near enough identical but costs
even more.  I won't quote a price as it has probably changed from when
we bought the proper WJ one for work three years ago, but look at
"similar to a top of the range amateur HF transceiver"    US operators
may well find it is considerably cheaper over there.

Andy  G4JNT

> ----------
> From: 	Peter Dodd[SMTP:g3ldo@zetnet.co.uk]
> Reply To: 	rsgb_lf_group@blacksheep.org
> Sent: 	2000-05-18 10:11
> To: 	rsgb_lf_group@blacksheep.org
> Subject: 	LF: Re: LF receivers 
> 
> I am working on the Receiver chapter for the LF book. I have a good 
> introduction written by John 4GVC (with a description of the TS850, 
> which caused many of us, including myself, to go this route) but 
> would like to bring it up to date in the light of your collective 
> experience. While I was up at Crawley I found that Derek was using 
> the 990 to good effect.
> What is your favorite receiver and how does it compare with others 
> that you might have tried?
> 
> 
> -- 
> Regards, Peter, G3LDO
> 
> <g3ldo@zetnet.co.uk>
> 
> 


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