Barlow Wadley XCR-30 Mk 2 FM
Rupert Goodwins
I picked up one of the above receivers -- 0-31 MHz analogue synthesis,
AM/SSB portable -- at a flea market in London last weekend, and I'm
very glad I did. Very interesting piece of radio history, and I'm
amazed at how much it does with a handful of transistors, at how well
it works after thirty years, and at what a pleasure it is to tune
around with. Looking inside, I bet I can keep it going for another
thirty years as well -- nothing there that can't be fixed.
The only insect in the face-cream is the telescopic antenna (I seem to
be cursed with these things). This has a very non-standard ball and
socket joint at the base, and has lost the top couple of feet. If
anyone has a spare, I'd love to hear from them. Otherwise, it's a
rebuild job -- and I've never managed to carry that off successfully.
Oh, and does anyone know why the synthesis system's called a Wadley
Loop? It's very clever, but I can't see a loop in there anywhere --
which makes it all the cleverer, of coruse, but still.
R
rupert goodwins
---------------
rupertg at cix dot co dot uk
Dave
Scroll down to "Design" (Talking about Racal 217)
"The receiver is a triple conversion super heterodyne design with an
interesting selection of IF frequencies, oscillator injection, and
control, which is often called the "Wadley Loop". This idea was
originally conceived by Dr. Trevor Wadley who used it for a stable
Wave meter he designed during the 1940s. This receiver is unlike any
normal super heterodyne, as the local oscillator is injected twice, at
different points, which eliminates any oscillator drift or
instability. RACAL have made several receivers using this principle,
as have other manufacturers such as Drake, Barlow, and more recently,
some Japanese companies.
The theory behind this, is that most oscillator drift and instability
occurs in the first converter, so if you can get rid of this, then the
receiver will be stable. One way is to use a fixed down converter with
crystal control and a tuneable IF frequency. Another way is to design
a very stable oscillator. A third way is to cancel out any drift and
this is what the Wadley Loop does. It achieves this by mixing the
received frequency up to a high IF frequency (40 mcs in this
receiver). It uses the SAME oscillator to generate a lower frequency
(37.5 mcs in this receiver). These signals are then remixed to
generate the second IF frequency. Any drift cancels out!"
On Sun, 14 Apr 2002 23:58:28 GMT,
rup...@charlieindiaxray.charlieoscar.uniformkilo (Rupert Goodwins)
wrote:
John Batty
I've got one of these beauties too [without the FM mod though :-( ]..
bought it second-hand about 1983, carried it around in kitbags and
cartons through a dozen moves, and it's still going strong. Great
piece of gear, it's still used as a backup receiver in the shack. The
"manual" :-) is printed on 2 sides of an A4 sheet - if you'd like a
copy let me know and I can scan it and email it to you.
Cheers
John Batty VK4MBK
http://www.shortwave-with-a-difference.com
colin newell
> Oh, and does anyone know why the synthesis system's called a Wadley
> Loop? It's very clever, but I can't see a loop in there anywhere --
> which makes it all the cleverer, of coruse, but still.
That is a phase lock loop they are talking about, a device
that would revolutionize world-band receiver technology..
As for the antenna..I have a friend who has an XCR-30..
he loves it.. however.. no spare antenna..
Colin
--
espresso.ts.uvic.ca World Band Radio Resources since 1994!
www.coffeecrew.com Espresso & Coffee Resources | Machines & Beans
Rupert Goodwins
<NOrn...@vcn.bc.ca> wrote:
>Rupert Goodwins <rup...@charlieindiaxray.charlieoscar.uniformkilo> wrote:
>> Oh, and does anyone know why the synthesis system's called a Wadley
>> Loop? It's very clever, but I can't see a loop in there anywhere --
>> which makes it all the cleverer, of coruse, but still.
>
>That is a phase lock loop they are talking about, a device
>that would revolutionize world-band receiver technology..
Yes... but the Wadley Loop isn't phase locked, and it's not a loop.
It uses some clever mixing tricks to cancel out drift and tune each
band in 1 MHz chunks with equal linearity. There's no feedback,
whereas a PLL divides a VCO output by a variable amount and compares
the result with a crystal reference, pulling the VCO to lock the
phases.
I do like the Wadley Loop, even if those three mixers in the signal
chain and the very rich harmonic stew cooked up inside make for some
interesting times. In terms of how much cleverness you get for so few
active devices, I think it's unsurpassed: I guess my Sony 7600 PLL
receiver has got about ten thousand active devices if you count the
transistors inside the CPU and so on; the XCR-30 has around fifteen,
and does the job just as well. It even has memories! (well, it has
replaceble log cards that slot into the holder abover the dial:
non-volatile, mind)
>As for the antenna..I have a friend who has an XCR-30..
>he loves it.. however.. no spare antenna..
>Colin
Ah well. I've bodged something from an old FM set, but I'd still
rather get an original spare.
>--
>espresso.ts.uvic.ca World Band Radio Resources since 1994!
>www.coffeecrew.com Espresso & Coffee Resources | Machines & Beans
rupert goodwins
mana...@gmail.com
I have 2 Barlow Wadley XCR-30 Mk2 receivers, one with FM tuner and the other without. I worked for Barlows at their Parow Industria factory in Cape Town South Africa during the time when they still manufactured them and was instrumental in their assembly and fault finding. Anyway, I havn't used either of them for several years since I was getting frequency drift and BFO howling on SSB and clicks throughout the rises between 12 to 30Mhz. Unfortunately, when the factory shut down their Wadley production line, I wasn't in time to take my Wadleys to the factory to have them realigned. Its been many years since. Quite recently decided to resurrect them because I looked at buying the WR-G303i Winradio but its just prohibitively expensive. Besides I would not be getting much more than I already have. Does anyone out here have the setup instructions for the S curve adjustment on a wobbulator. It would be greatly appreciated if someone can help me in this regard.
Thanks
Faried Manan.
dave
DhiaDuit
worldofg...@gmail.com
Thank you
giorgio...@libero.it
George Cornelius
If you are asking about newsgroup logs, I certainly do not know how to
look up things in old messages using my normal tools. Google Groups
probably has a way, since it is based on the old Deja News archive.
Others here may know how to do this.
Another idea is to subscribe to a news (Usenet) provider that has a
lot of messages still cached. But I would not expect more than just
a few years online.
Also: try other newsgroups, such as sci.electronics.* and especially
electronics-related groups with names ending in .repair .
George