 |
BW LITERATURE
|
In this part of site, we put ALL
what I can find on the Internet or not, related with the BW outside
than original Barlow Co. tech literature (see):
Receiver tests, user impressions, receiver usage tips and more!
Here is the links
to jump directly to the parts of your interest:
 BARLOW
WADLEY XCR-30 (by Lawrence Magne)
Barlow Television Co. P.O.Box 23, New Natal,
ZA. List price (1978) 269 US $
Highlights: Advantages:
Superior SSB reception, sensitivity and selectivity. ECSS
capability. Low battery drain. Rugged case. Disavantages:
Overloading not defeatable, in the presence of strong nearby
signals. No FM reception (US Only). Poor FM reception (outside
USA). Poor MW reception. No AC Input. No dial light. Overall:
An obvious choice for SSB/CW or ECSS listening. Preferred
for portable DX-ing. A variety of shortcomings makes other
portables more suitable for general shortwave broadcast listening.
The
Barlow Wadley XCR-30 is
the first direct readout shortwave portable to come on
the market, has much to commend it. It's both sensitive
and selective. Excellent reception of SSB/CW signals makes
it a top choice of hams, and its rugged metal case is
a pleasant change from the usual plastic variety.
For seriuos DX-ing, it is the only portable - indeed,
the only set tested listing under $450 - that is capable
of exalted carrier selectable sideband (ECSS) reception.
For energy conscious listeners, the XCR-30 uses far less
battery power than other sets tested.
Unfortunately,
the XCR-30 has not kept pace with times and, except
for ham and DX use, has become relatively less desiderable
than the newer portables for general shortwave listening.
Its front end overloads in the presence of strong signals,
and no attenuation control is provided to alleviate
the problem.
Strong signals tend to break through
1 Mhz away, even with careful tuning.
There's no dial
light. Mediumwave performance is poor - only the strongest
stations appear.
The battery holder
allows the cells to tumble into the circuitry. The first
RF transistor is prone to "blow" when minor
static discharges enter the antenna.
XCR-30 owners are advised to touch the antenna only
after discharging any static eletricity they may have
accumulated, e.g. when walking across a carpet.
|
There
is no AC Input. The FM tuner, when available, performs
poorly.
Within the United
States there are additional difficulties. First, the
optional FM tuner is not certified by the Federal Communications
Certified as meeting requirements concerning spurious
radiation. It is, therefore, illegal to import for resale.
Second, there have been difficulties obtaining the XCR-30,
within the US in recent months. As of press time, the
set appears to be unavailable in that country.
Quality control
problems with the XCR-30 have persisted since its introduction,
although the worst of the soldering problems have long
since been cleared up.
Those considering the set should, if it all possible,
test beforehand any sample they wish to purchase the
set with a money-back or exchange guarantee.
We have had an
XCR-30 for laboratory and field use for over two years
and, despite its problems, continue to find it useful
to complement other portables when signals are unusually
weak or subject to severe interference. It has a unique
place in the listener market and for certain non-listener
applications. It is a superior DX and amateur portable.
If it is redesigned
to eliminate the major shortcomings - not unlikely,
as it has been some time since the last version, the
Mark II, appearead on the market - it could be an excellent
receiver.
However, as of now most shortwave broadcast listeners
will probably prefer one of the newer Japanese or German
portables.
TOP PAGE
|
|
|
| The
Barlow Wadley XCR-30 Receiver - QST Test
Jan 1977 (by W1CP)
The Barlow
Wadley XCR-30 portable receiver provides frequency
coverage from 500 Khz to 30 Mhz. It is powered by six
1.5 volts cells (nine volts overall) which are fitted
into a battery case inside the receiver.
The XCR-30 is capable of receiving upper or lower sideband
and AM.CW can be received by placing in one of the sideband
modes. There is a fine tuning adjustment called an SSB
CLARIFIER, two tuning dials are used, one for setting
the Mhz range and the other dial provides 1000 Khz coverage
with 10 khz dial markings.
It is easy to tune the receiver to within a kilohertz
or two of a predetermined frequency with some accuracy.
A volume control and a antenna-peaking control are also
located on the front panel. Additionally, there is a
ZERO SET control which is used for exact frequency setting
to compensate for temperature or humidity variations
should such adjustement be necessary.
The built-in antenna is of the telescoping whip variety
and is approximately 40-inches long, when fully extended.
Provisions are made for an external antenna. But the
receiver is designed for maximum performance using the
whip, I found during my use of the receiver that the
whip did a creditable job.
|
Circuit
Details
Fig.1 provides
the general information of signal paths. Assume an incoming
signal of 13.7 Mhz, with the Mhz dial set at 13 Mhz,
the Mhz set oscillator will be at 58.5 Mhz. This, mixed
with the incoming 13.7 Mhz signal, produces the first
IF of 48.8 Mhz which is amplified and fed to the 3rd
balanced mixer. The 58.5 Mhz set oscillator signal is
fed to another mixer where it is combined with the output
of a harmonic generator. The harmonic generator is based
on a 1 Mhz crystal oscillator which produces a signal
at 1 Mhz intervals. The only signal appearing in the
harmonic filter is the 58.5 Mhz signal and 16th armonic
of the harmonic generator. These signals produce the
42.5 Mhz signal which is amplified and fed to the 3rd
mixer along with the 44.8 Mhz signal. The resultant
signal is a 2.3 Mhz which is fed to the 2 to 3 Mhz interpolation
section of the receiver. The Khz dial to 700 will, therefore,
tune this section of the receiver to the 2300 Khz signal
coming from the 3rd mixer.
The maximum audio power is 400 mW which seems more than
adequate even in noisy outdoor environments. There is
also a headphone output available.
Selectivity is rated by the manufacturer at 6 Khz for
AM and 3 Khz for CW/SSB. I found the selectivity adequate
for listening, even on the crowded amateur bands (and
the 11 meter CB frequencies).
The receiver is a full fledged communications type,
not a toy. I tried the receiver with a separate transmitter
and found it would do a noteworthy job.
There are many uses for a portable, general-coverage
receiver. I used the receiver to chase down a noisy
power-line pole in one instance.
In another, the receiver came in handy for the on-site
antenna work to check a grid-dip meter for proper operation
and frequency accuracy. Battery power consumption is
low - 20 mA with no signal up to 200 mA at full audio.
- W1CP
TOP
PAGE
BACK
TO TECHS FACTS
|
|
|
THE BARLOW
WADLEY XCR-30:
A REVIEW (By MICHAEL
S. HARDESTER)
In the brief 5 years I have
been an active DX'er, few portable receivers have
been made available to the public which have proved
to be of any value to the DX'er planning a DXpedition
or going on vacation. One excellent receiver was
the Realistic TRF; however, before its true value
was realized, it was taken off the market. About
the same time the TRF was making news, another
receiver was being born, but it wasn't until late
1972 that any
real attention was placed upon the receiver from
South Africa: the Barlow Wadley
XCR-30.
Currently available in the
United States through Gilfer Associates, Box 239,
Park Ridge, New Jersey 07656, the XCR-30 was retailing
for US $255 in 1974.The owners manual has this
to say about the XCR-30:
"The XCR-30 is a specialized,
high sensitivity portable shortwave receiver,
designed to provide precision frequency tuning
over the full shortwave spectrum up to 30 mHz,
with exceptional frequency stability for both
amplitude modulated (A.M.) and single side-band
(S.S.B.) transmissions." The circuit is a
"multiple heterodyne circuit.... incorporated
wherein the harmonics of a 1 mHz quartz crystal
control the frequency shown on the dials to an
accuracy sufficient to locate and identify a station
whose frequency is known. The crystal stabilizes
the received frequency to eliminate tuning drift
over long periods of time and to provide stable
single sideband pitch. Frequency selection is
a composite function of two dials.
One dial displays the mHz
segment in whole numbers (e.g., 1,2,3, and so
on to 30) 7 the second dial displays the mHz segment
(e.g.,.000,.010,.020, and so on in increments
of .010 mHz up to 1.000 mHz). To tune a frequency,
the whole number dial is set to
the mHz segment (e.g., 11),and the fractional
mHz segment is set to a fraction (e.g.,.950),
thus the frequency is 11.000 + .950 = 11.950 mHz.
It takes a little practice to get the hang of
the dials, but once practiced, it's done without
thinking.
Modes of reception are AM,
CW, and SSB (USB & LSB) with a tuning dial
to clarify SSB signals as well as AM signals.
In addition to the mode selection switch and on/off/volume
control, the tuning dial is accompanied by a fourth
dial: the antenna trimmer - for peaking incoming
signals. A S-meter (of sorts) is built in, but
at time it may indicate a low reading for a local
station (e.g., KTRS-860 with 10 kw beaming directly
at my QTH) and shortly thereafter, a high reading.
The XCR-30 is designed to operate
off of six (6) type "D" dry cell batter-
ies (each 1.5v) for a total D.C. input of 9 volts.
An external power soc-
ket is provided for a power supply of 6 to 12
volts inputo Two other plugs
are present: an ear phone jack ( 8 ohms) and external
antenna jack. The
receiver comes with a built-in whip antenna; however,
I have found it only of use for casual listening.
On Medium Wave, I have utilized the Space Magnet
antenna manufactured by Worcester Electronics
Labortory. RD # 1,
|
Frankfort,
New York 13340. On the shortwave frequencies, the
XCR-30 manual suggests that any longwire employed
should not exceed 50 feet in length, to minimize
cross modulation; however, I am currently using
a 100 foot long-
wire with little cross modulation being noted on
shortwave.
Frequency readout is 10 kHz over each 1000 kHz range
and calibration accur-
acy is within 5 kHz on all frequencies with resetting
accuracy within 1 kHz
on all frequencies. Utilizing a BC-221-M Frequency
Meter, I can attest to
the above claim of 5 kHz accuracy. The resetting
accuracy also checks out
as correct to within 1 kHz on all frequencies. I
should point out, however,
that I can only make this claim from .5 to 20 mHz,
as the upper limit of
the BC-221 is 20 mHz. Unfortunately, I do not have
the means of checking
above 20 mHz.
Sensitivity is excellent on all frequencies utilizing
the Space Magnet or
the longwire. Though the built-in whip is not used
while DX'ing, East Coast
stations such as KDKA, WSB, WBZ, etc., are heard
with fair signals, but
not as well as when using the Space Magnet antenna.
On the shortwave bands,
I was unable to find any station on my Hammarlund
HQ-129X which was not
audible on the XCR-30. Though the signals on the
HQ-129X were sometimes
stronger than on the the XCR-30, the Barlow Wadley,
pulled each signal in
to an audible level at least.
Selectivity is 6 kHz overall RF on AM, and 3 kHz
overall RF on SSB and CW. In actual use, I have
found AM selectivity to be from 4 kHz to 30 kHz
depending on the station being monitored. The 4
kHz was determined from VSZ-1 on 844 kHz with WHAS-840
on the air. The 30 kHz was from local KTRB-860 occupying
830 to 890 kHz during the day, and slacking off
at night only to the extent of allowing KRVN-880
to come through. This is true regardless of the
type of antenna: whip. Space Magnet, or longwire.
On the Shortwave bands, selectivity is usually 5
to 10 kHz with the Voice of America occasionally
pushing it to 25 or 30 kHz.
The Barlow Wadley XCR-30 is a prototype receiver,
somewhat new to North
America. At the present, an XCR type receiver is
being planned to include the FM band. This was excluded
in the current models "to eliminate the possibility
of cross modulation." Unfortunately for the
designers, they
neglected to guard against cross modulation from
locals, but then, what receiver is totally free
from the products of cross modulation? Possibly
the only other "complaint" I can put forth
is that concerning the lack of selectivity regarding
locals. However, keeping in mind the fact that the
XCR-30 is a portable receiver, I feel it is equal
to many non-portable receivers, and should be recognized
as an up and coming piece of equipment in the DX
field, whether for a main receiver or as a portable
receiver
for DXpeditions or vacations.
(Courtesy
by National
Radio Club P.C.)
TOP
PAGE
|
|
|
|
THE
BIG MATCH
(By FRANCOIS STEYN)
A very sensitive
issue has finally (?) been settled. After the receiver
review for the SONY SW55 appeared in the Jan/Feb. 1993
issue of the SASWL, voices have
been heard questioning some of the remarks and results
published in the review. The matter was complicated
further with the receiver ratings for portables in the
1993 WRTH, this time rating the SW55 overall better
than the Drake R8.Some of the local SADXers then decided
to get together to test some of the current portables
under portable conditions, i.e. running on batteries
and only using their whip antennas.
One of the arguments aired regularly was about the use
of modern portables as portable sets and not as quasi-tabletop
sets by adding external antenna and earth connections.
We were interested to see which portable would perform
best (sensitivity/ audibility / performance ) when used
on its own. I went along as a bystander, as I am not
lucky enough to own one of these modern wonders. For
interest sake I took along a
Barlow Wadley XCR30 of 1973 vintage.
The testing started at 1500 UTC at Jimmy Lambert's QTH
in Orange Grove, Johannesburg and was attended by a
number of local SADXers. The following receivers were
tested:
SONY SW55
SONY SW77
SONY 2001D
Grundig Satellit 700
Sangean 803A
Sangean 808
Panasonic RFB 60
Barlow Wadley XCR30
(Two SONY 55's and three SONY 2001D's were available,
all from different batches.) Two more Barlow
Wadley's, the older Grundig 2100 and a SONY
7600 were tried as well. All the test receivers were
operated on a large plastic garden table, away from
large metal objects to reduce earth coupling.
A 0-8 rating was decided on in the following categories:
Sensitivity on Shortwave (as checked on three frequencies),
Sensitivity on Medium-wave, Selectivity and Ease of
use. For Audio judgement a scale of 1 - 10 was used.
The following results were recorded:
| Receivers |
SW
Sens |
MW
Sens |
Audio |
|
|
|
|
| 2001D |
2+1+3 |
1 |
5 |
| SW
55 |
3+3+1.5 |
0 |
3 |
| SW
77 |
0+0+1 |
0 |
3 |
| Sangean
808 |
0+0+0 |
0 |
2 |
| RFB
60 |
3+3+4 |
0 |
6 |
| Sangean
803A |
4+0+0 |
0 |
8 |
| Grundig
700 |
2+0+0 |
1 |
10 |
| Barlow
Wadley |
4+5+6 |
3 |
8 |
(A "0"
indicates that the required station was not received)
|
As
far as the "Audio" category was concerned there
is nothing that beats the Grundig Satellit 700: this is
true especially in the "in the open" situation
as we tried it in the garden. With its separate bass and
treble controls and large front-mounted speaker it is
much easier to adjust the audio than on the other sets
tested. On the other side of the spectrum we found the
audio from the Sony 55's letterbox slot disappointing,
taking its price into consideration. As John Plimmer said:
"Sounds worse than a telephone connection..."
.The sound from the RFB 60 was nice and crisp.
Both the Barlow Wadley and Sangean 803A
with their front-mounted speakers delivered enough volume
to be used in the garden.
What happened to the selectivity and "ease of use"
categories you may ask ? As far as the selectivity test
was concerned : it, aim was to see which portable could
receive a weak broadcast next (+/- 5kHz) to a strong one
with the least splatter. The Barlow Wadley XCR
30 came out tops on 17845 kHz (D.Welle) where
a weak station was easily heard next to 17850 kHz (R.France
Int.) ……. all the other sets could not even
hear the weak one on 17845 kHz.
When comments were exchanged about the "ease of use"
category, chaos broke loose as owners tried to push their
Sets as easy to use due to its number of memories, number
and size of buttons, scanning, etc. Maybe the answer can
be found in one of the comments heard: "How long
will it take the listener to master all the buttons when
he first get the radio ?? Although the Barlow
Wadley has no memories or scanning, its operation
is pretty straightforward.
After checking the score sheets the following results
were apparent:
Tested for its ability to flush out weak An stations (DX)
the order of scoring was as follows:
No: 1) Barlow Wadley XCR30
2) National Panasonic RFB60
3) SONY ICF 2001D
4) SONY SW55
5) Sangean 803A
6) SONY SW77
7) Grundig Sat.700
8) Sangean 808
So what can be concluded ? Although hailed as an outstanding
portable, the SONY SW55 did not really impress as far
as performance is concerned. The much lower rated RFB
60 did a much better job of getting the weaker ones that
all the others (except the Barlow Wadley).
And last but not least : the 20 year old Barlow
Wadley is on top, its AM SW capabilities not
aged at all ! It is like Jimmy Lambert said :
"My Barlow Wadley's have just gone up in
value !!"
(Published in
THE SA SW LISTENER, April 1993)
Courtesy of Francois
Steyn
TOP
PAGE
|
|
BW
XCR-30: PART 1
THE PROBLEM
by Piet Conradie
Looking through the results of the recent club survey,
it is evident that the South African made BARLOW WADLEY
XCR-30 receiver is still very well represented among members.
Being the owner of three of these portables, I
was prompted to do some reflection on the WADLEY. On it's
arrival about 20 years ago, the XCR-30 was hailed as the
most
remarkable development in portable receivers for many
years. It was completely different from all other available
portables it provided
unknown precision frequency tuning over the full short
wave spectrum up to 30 MHz but it completely lacked the
customary wave band switch. It was so stable on a tuned
frequency that excellent SSB reception was possible.
The Dec 1975 ELEMENTARY ELECTRONICS review read: "The
BW is the finest portable receiver we have ever seen or
used, and we'll include those famous trans-oceanics of
years past.
The XCR-30
is also a lot better SW
receiver than a lot of high priced equipment sold to
amateurs and general short wave listeners." At
that time the BW was available the USA by mail order
from Gilfer Associates for $290. (1$ approx I 1R in
1975 !)·
|
WHY
WAS THE XCR-30 SO SPECIAL?: To understand why the XCR
made such an
impression at the time, we must note that between about
1930 to 1970 there was little change in shortwave receiver
design. The trusted super-heterodyne circuit was the work-horse
of the day. The main change
during this period was the move from valve to transistors.
Transistor receivers with low voltage and power consumption
required inexpensive small batteries and thus made the
ownership of radios possible to the
millions, also to people in remote parts of the world.
Dxers resorted to all kinds of ingenious methods to solve
this problem, including interpolation on a band-spread
dial if the frequency of two or more marker stations were
known. More well-off DXers used an expensive device called
the BC 221 Frequency Meter. Though reasonable accurate,
the BC 221 was a bit of
an inconvenience to operate.The world was ready for an
answer to this problem. I intend to take brief looks at
items such as the man who designed a solution to the problem,
the acceptance of the XCR-30 world-wide, a block diagram
of the XCR-30, the wadley loop, what the competition has
done and close with a present evaluation of the receiver.
TOP PAGE |
|
|
BW
XCR-30 : PART 2
PROBLEM SOLVED!
by Piet Conradie
DR WADLEY: To trace the origin of the XCR-30 we must
mention a man called Dr Tevor Lloyd Wadley (Born Durban
1920, Died Warner Beach, Natal 1981), who is well known
for designing the wadley loop and the TELLUROMETER.
About 1950 dr Wadley worked in England on RACAL's RA17
design team. At this time he conceived a circuit which
has become known as the wadley loop. This circuit was
implemented in the RACAL receiver - a unit costing thousands
, of Rand at the time. Dr Wadley returned to South Africa
- he was working for the CSIR in l954 when he designed
the TELLUROMETER. This device used radio waves to measure
distance. The Tellurometer brought a world wide revolution
in geodetic surveying methods. Dr Wadley did not forget
his loop in the RACAL receiver and finally succeeded
in designing a circuit for a portable receiver using
the same principles, but obtaining a less expensive
end-result.
This receiver was built by BARLOW's Radio Factory in
New Germany, NATAL Since the start of the 70's. The
receiver's full name: BARLOW WADLEY XCR-30 can
now be accounted for: "XCR" means X-tal (Crystal)
Controlled Receiver and the "30" refers to
the frequency coverage up to 30MHz.
VARIATIONS: Up to 1974, BARLOW's made several changes
to the BW circuit.
These are documented on the final
circuit diagram. Several small changes were made
including a switch to a different transistor type. The
most severe change was the replacement of the transistorised
audio section by a single IC and the provision of a
frequency calibration control.
Externally the face plate was changed from a chromed
appearance to grey to a military
|
green.
It was always felt that the BW was not very sensitive
on MW.
A club-member from Durban, David Hotchkiss in Aug 1975
offered an active MW antenna at R15 to members. I have
one of these and it still works well.
UNIQUE PORTABLE: DXers immediately realised that
the BW was a most unusual receiver with continuous tuning
from 0,5 to 31 MHz while having the same frequency resolution
at 1MHz as at 30MHz and frequency calibration accuracy
of 5kHz.
SA DX CLUB MEMBERS'
REACTION : Tracking the history of the BW within the
Club by looking in old issues of DX-NEWS, the former
name of the SADXC Bulletin, I have noted 2 BWs in the
Totem Pole of Sept 1971. (MY first BW was bought in
Dec 1971.) From 1972 the Club had a special offer for
members from BARLOW's for the BW. The offer to the SADXC
was available for many years - in 1972 the basic receiver
was available for R115 and a FM add on module was available
for R20. By 1975 the special price had risen to R137.
The special offer was gladly taken up by members and
the move to the BW was on. By Nov '72 8 BW's were listed
in the Totem Pole. In 1977 the BW was probably at its
peak popularity in the club when 9 of the top 12 DXers
in the Totem Pole were using the BW. The shop price
of the BW peaked at about R260 in 1980.
THE BUYERS : I think
that although the BW was initially designed for South
African conditions, most units found owners in Europe
and North America. Looking through the "I listen
to Radio Japan" photo's on the back pages of Radio
Japan News published during the 1970's you will see
many proud DXers from all over the world showing off
their BW's and that must be
only a very small percentage of overseas owners. South
Africa just did not have the market to absorb a large
number of specialised receivers. Also during the time
of the BW's production run, there was a move away
from shortwave in South Africa because the SABC provided
better FM coverage to the remote parts of the country.
TOP PAGE
|
|
|
BW
XCR-30: PART 3
A VERY SPECIAL CIRCUIT
by Piet Conradie
The wadley
loop consists of a triple-conversion super-heterodyne
system.
This offers a number of advantages in terms of performance
above other circuits used previously.
SOME NOTES
ON THE BLOCK DIAGRAM: (Please refer to Part 3) A high
first
intermediate frequency (IF1) is used (45 MHZ) giving
good image (second channel) rejection. The problems
inherent in achieving satisfactory frequency stability
in the first oscillator <MHz SET>, which operates
in the VHF band tuning over a range of 30MHz (45-75MHz),
are overcome by mixing its output in twice, so that
any errors due to drift are self cancelling. This is
done in Mixer 1 by mixing the <MHz SET> oscillator
output with spectrum of harmonics from a stable 1MHz
crystal oscillator. The product at 42,5MHz is selected
by the Harmonic Filter and mixed in Mixer 3 with the
1 MHz wide band of signals at 45MHz coming from IF1
to translate them to the band 3-2 MHz for IF2. The 1MHz
band of signals at 45MHz is the output of Mixer 2 where
the <MHz SET> oscillator frequency and the tuned
RF is mixed. The outputs of IF2 and the <kHz SET>
oscillator is mixed in Mixer 4. It is relative easy
to make this mixer adequately stable as it operates
at a reasonably low frequency with a bandwidth of just
one MHz. The output of Mixer 4, which is at 455krHz,
is passed on to a conventional IF3 filter/amplifier
chain, detector and AF stages.
|
FUNNY SIGNALS: One of the
mysteries of the BW can now be explained by studying
the Block Diagram. Most owners will have noticed that
besides the harmonics of the crystal oscillator on 1MHz
multiples, there are two other ever present immovable
signals: one on 2,7275 MHz, and another on 3,2275 MHz.
The last one is especially bothersome as it is located
within the 90-m band.
The answer as to the origin of these
signals is that, for the specific frequencies, the <kHz
SET> oscillator must run at the same frequency as
the desired tuned <MHz/kHz SET> frequency in order
to produce a 455kcHz product for the final IF section.
E.g.: an original tuned RF of 3,2275 MHz is converted
in Mixer 3 to 2,7725 MHz. A 3,2275 MHz frequency is
needed from the <kHz SET> oscillator to produce
a 455 kHz product in Mixer 4. Due to insufficient screening,
the oscillator's output is picked up by the receiver's
RF front-end, which of course is tuned to the same frequency
as the <kHz SET> oscillator.
The exact frequency of the
455 kHz IF depends on the actual ceramic filters used,
this might differ a few kHz from 455. This will cause
the exact position of these stray signals to differ
a few kHz from receiver to receiver.
wadley loop ADVANTAGES:
We have already mentioned the good image rejection characteristic
of the wadley loop. The fact that there are no conventional
band switches (except in the antenna trimmer) excludes
varying contact resistance which is a common cause of
instability in oscillator circuits. The tuning resolution
of the receiver is the same at 1MHz as at 30MHz, because
the whole range of 0.5-30MHz is tuned in bands 1MHz
wide.
Being locked to the harmonics
of a 1 MHz crystal, the wadley loop's frequency tuning
is very stable.
wadley loop DISADVANTAGES: The large number of mixing
stages used, calls for careful screening and filtering,
if spurious products are to be kept low. Efficient filters,
operating in the VHF band, must be designed for IF1
and the 42,5MHz Harmonic Filter. Another problem is
that the output of the harmonic generator at exact multiples
of 1MHz causes great difficulty, when listening to time
signals from stations like WWV.
TOP
PAGE
|
|
BW
XCR-30: PART 4
CHALLENGE FROM THE EAST
by Piet Conradie
In Japan radio engineers were compelled to study Dr Wadley's
revolutionary achievement, and then began manufacturing
portable and table model shortwave radios containing multiple
conversion features. To provide linear analogue frequency
readout without using the complex wadley loop, some receivers
like the Sony ICF-5900 and the Panasonic RF2200
utilised "Rube Goldberg" schemes. Other radios,
e.g. the Yaesu FRG-7 used the wadley loop in a circuit
which was an improvement on the pioneering XCR-30 design.
For instance, in the FRG-7 a higher first IF (55 MHz)
was used, against the XCR-30's 45 MHz. In many wadley
loop receivers the designers tried to save by having IF2
fixed-tuned with a 1 MHz pass-band, but in the XCR-30
and FRG-7 it is tuned in step with the <kHz SET>
oscillator. (Refer to Part 3: Block Diagram & Part
4: wadley loop) For most of 1977 a lone first FRG-7 featured
in the SADXC Totem Pole. By March 1978 members were welcoming
the invaders from Japan with open arms - already 8 FRG-7's
were heads-on with 10 BW's. |
(The
of same DX-NEWS also contained a 4 page review of the
FRG-7.) Some new FRG-7 owners were ex-BW owners, so clearly
the move away from the BW had started.
THE END: The appearance of these
advanced receivers on overseas markets and the development
of Phase Lock Loop circuits and more accurate digital
readouts on LCD screens finally killed off the demand
for the BW. Production of the XCR-30 at BARLOW's Radio
Factory finally ceased after about 10 years. I believe
no more than 20 000 BW's were made. At the end of 1981
large stocks of the BW were sold on special offer at
R99,88 (+ 4% sales tax!) by a discount store in Cape
Town. Many existing BW Owners (including myself) grabbed
the chance to obtain another BW.
#17928 became a partner for my original #0512. At the
same time I bought a "deceased" BW (#0372)
from another second-time owner for R20 with the intention
to keep it for spare parts to maintain my other BWs.
After being tucked away in a dark cupboard for several
years, I managed to locate this set's problem to a dry
solderjoint in one of the Air Coils. Itis now in perfect
working order.
In 1979 Dr
Wadley's face appeared on 1,9 million postage
stamps commemorating the 25th year of the Tellurometer
invention...
TOP PAGE
|
|
|
BW
XCR-30: PART 5
S-METER STILL KICKING
by Piet Conradie
Judging from 20 years experience,
there is not much that can go wrong with the XCR 30
and if cared for, most units should easily make it well
into the next century. The set does not suffer from
the static electricity problem which turns many modern
day FET front-ends into expensive repair bills. Neither
has it a LCD screen which will fade away after a number
of years or an on board computer which might 40 on the
blink when the receiver-specific component has not been
manufactured for some years.
Most electrical parts used in the BW are still readily
available off the shelve. Most of my problems centred
around the antenna trimmer. I once had to replace a
broken cord. At one stage it was evident that the contacts
of the micro switches in the antenna trimmer were not
making a 100% contact as they should. I carefully opened
the switches, cleaned them and managed to restore satisfactory
operation. While not having the proper signal generator
and oscilloscope to perform proper alignment of the
BW's circuits, I have never the less succeeded in aligning
my BW's to my satisfaction.
One such method is to use
a very weak input signal, like HCJB's SSB signal on
25950 kHz, and then peaking the various circuits by
ear. I am not suggesting you should try it I am just
saying it can be done! Comparing my BW's to a present
day state-of-the-art receiver, by using for instance
the same weak SSB signal from HCJB, the BW's regularly
manage to outperform my WBR2000/ATS 803A with regard
to sensitivity.
|
This
is probably due to the fact that the WBR2000 does not
enjoy the benefit of an antenna trimmer. If I travel away
from home, I do not hesitate, the BW is my receiver of
choice. The WBR2000 only starts to match the BW with regard
to sensitivity when a suitable outdoor antenna is attached
to it. Of course the BW cannot match the WBR on other
points. It has no memories or push button frequency dialling.
It lacks the accurate frequency read-out of the WBR2000.
It does not have a choice of wide and narrow filters.
The BW also easily overloads on a longwire. The end result
is that I use the two receivers in conjunction to complement
each other. As many DXers do, it also allows me to search
for parallel frequencies while using both receivers.
On it's own, the BW can still be regarded as a very adequate
portable Receiver. If You are in the market for a second-hand
receiver and a good operational BW comes your way, you
should give it careful consideration,
provided the price is reasonable. I have recently seen
an ad in Radio ZS [local amateur-radio magazine] for R550
one. Whether that was reasonable I am not sure, but compare
it to the R800 for a new WBR2000 or more than R2000 for
a SONY 2001D. By the way, I have no BW's for sale!
Treat your BARLOW WADLEY with respect. It was the first
of a new generation of vastly improved receivers which
we are able to enjoy today.
TOP PAGE |
|
BW
XCR-30: PART 6
MORE HISTORY - TIPS FROM THE PAST
by Piet Conradie
BEGINNERS GUIDE TO DXING written by G.E. WOOD (OM Gerry
was for many years the editor of DX-NEWS, the earlier
name of the SADXC's bulletin) and published 1973, unveils
the BW's first days. It states that Dr Wadley "produced
the design for the XCR-30 in about 1969. A prototype of
the set was used in the first Cape to Rio yacht race and
gave excellent results. The receiver came on the market
in early 1971." This same publication contained a
HAMRAD ad for the XCR-30 warning that "due to export
commitments, however, there might be a delay in supplying
this Rolls Royce of receivers."
Last days: The XCR-30 was discontinued in 1981, the year
Dr Wadley died. Someone has made the following rather
interesting statement:The reason why the XCR-30 was discontinued,
is because Dr Wadley stated in his will that, on his death,
the XCR-30 should be discontinued."
Is any SADXC member able to verify this?
**S0ME EXCELLENT TIPS FROM YEARS PAST**
Questions from a SADXer in England : I have a XCR-30 and
I was wondering if the IF bandwidth can be reduced? Also,
how can reception in the MW-band be improved, how should
an external antenna be connected, especially if problems
are encountered with spurious signals and by what means
can spurious image rejection be improved ?
Answer by David Hotchkiss from Durban : (1) The IF bandwidth
of the XCR-30 is determined by the ceramic filters (SFD455B)
and the capacitors C63 & C64 (68pF) and C68 &
C71 (68pF).
On AM, the bandwidth is increased by paralleling C71 &
C68 with C63 & C64 respectively. The bandwidth may
thus be decreased, on AM, by reducing the value of C68
& C71, or by removing them altogether. Of course,
with this narrower bandwidth, speech will be less intelligible,
and music a mere unpleasant noise. is poor. The set was
(2) The performance of the XCR-30 in the MW-band is poor
: The set was designed
primarily for short-wave. The use of directional, tuned
loop or ferrite rod antennas will improve reception in
the crowded MW-band. [In my own experience, when not located
near a MW-transmitter, connecting an external antenna
directly to the telescopic antenna will work wonders for
MW-DXing. By using this method! member Cyril Hancock,
in 1976, reported having Increased his MW-loggings from
3 to more than a 100: Piet] |
(3)
An external antenna should be connected to the socket
provided, not to the telescopic antenna, to avoid de-tuning
of the antenna trimmer circuit. [Except on MW, as stated
above - Piet]
(4) For further image and spurious rejection, an Antenna
Tuner Unit (ATU) may be used, and the output fed into
the external antenna socket with the telescopic antenna
retracted.
The cross-modulation performance will never be very good
due to the use of bipolar transistors rather than Field
Effect Transistors (FETs) in the front-end and the first
IF stages. This interference originates in the receiver
before the IF filter, and thus cannot be "sorted
out" by using a narrower IF band-pass. The XCR-30
is good value for money, but professional performance
cannot be expected at the price!
Notes from the original "Operating Instructions"
for the XCR30
[For owners without this Important information]: (1) THE
MHZ DAIL: The MHz dial may be adjusted to eliminate certain
types of interference due to image channel effects. This
displacement shifts the images until they
cannot be heard, without affecting the main tuning. This
is an advantage of a multiple heterodyne design, over
a conventional heterodyne design, where such an image
effect cannot be shifted. An image effect Is usually heard
as a whistle, on the required station, which varies in
pitch, as the receiver is tuned. A whistle which does
not vary in this way, is usually due to other causes,
such as an adjacent station. Ensure that any interference
encountered, cannot be eliminated by a slight adjustment
of this dial.
2) THE ANTENNA TRIMMER: A strong station may not change
much audibly with antenna tuning but should nevertheless
be peaked up accurately on the meter, otherwise optimum
reception will be lost, should the signal strength weaken
or fade deeply. When searching generally over a limited
band e.g. an amateur band, or a particular broadcast band,
the aerial tuning may be peaked up on any station in the
band, or simply on the noise, and ignored until a station
is located for protracted listening, when a final touch
up may be made. This procedure is very effective over
most of the coverage of the receiver, but at lower frequencies
and the medium wave frequencies particularly, accurate
antenna tuning is usually called for.
(Original articles appeared in the SA SW Listener) - Courtesy
by Piet Conradie
TOP PAGE
|
|
THE
WADLEY SOUTH AFRICAN RECEIVER
By Keith R Thrower, Research Director, Racal Radio Group,
UK.
The British company
Racal Ltd had been interested in manufacturing the new
Collins 51-J HF communications receiver for the Royal
Navy in 1953, but had been turned down due to their facilities
being too small at the time. Upon his return to South
Africa after the war, Wadley incorporated the drift-cancelling
technique into a stable HF radio receiver. He produced
two laboratory models of these receivers, which combined
excellent frequency stability with high sensitivity and
high selectivity.
Apart from Government
sales, which did not materialise, SMD had hopes of capturing
a significant amateur radio market, but concluded that
the selling price would be too high. Whilst these six
receivers were being built, Wadley constructed two signal
generators, based on the drift-cancelling technique. One
of these was taken to England by Dr Frank Hewitt, who
was Wadley's boss and in charge of the Telecom Research
Labs of the CSIR (eventually becoming Vice President of
CSIR).
Hewitt had hopes
of finding a company willing to exploit the design commercially.
Before he had the chance to pursue this, he heard of the
Royal Navy requirement for a new HF receiver and that
the negotiations between Racal Engineering and Collins
Radio for the manufacture of the 51-J receiver had broken
down.
This information
came via a phone call from Mrs Vera Parnell, the Editor
of the CERCA Newsletter (Commonwealth and Empire Radio
for Civil Aviation). But all was not doom and gloom. Out
of the blue came Dr Trevor Wadley, who worked for the
South African Council for Scientific and Industrial Research
(CSIR). |
During the war years, Wadley
had worked for the Telecommunications Research Establishment
(TRE) at Malvern in England (later to become RSRE,
and more recently DRA).
Whilst at TRE, Wadley invented a unique circuit for
cancelling frequency drift which he used in the design
of a wavemeter - a circuit later to be known as the
wadley loop.
Careful screening was required to ensure stability
and to minimise
internally generated spurious frequencies. Once patent
protection was obtained, Wadley took the receiver
to the UK to find commercial interest, but was unsuccessful.
All the major UK companies gave the receiver the proverbial
thumbs-down. Back home, however, there was interest
from the SADF (South African Defence Force) and funds
were provided by CSIR for the manufacture of six prototype
models.
These were produced by SMD Manufacturing Co, whose
principal director was Horace Dainty (now retired,
but living with his wife near Durban) .
(Courtesy
by Francois
Steyn, ex editor of South African Dx Magazine ''SADXC
'')
TOP
PAGE
|
|
MORE
ABOUT THE LATE Dr. TREVOR WADLEY
The late Dr. Trevor Lloyd Wadley was one of South Africa's
most famous electrical scientists. He was born in 1920
and died on the 21st May 1981.
|
Trevor Wadley graduated from
Natal University College in 1940 with a BSc Eng (Elect)
and a DSc Eng from Wits University in 1959. He joined
the Special Signal Services (SSS) under his former professor
of physics, Colonel DB (Dave) Hodges. Trevor, worked
closely with Majors GR (Boz) Bozzoli and Frank Hewitt
(the latter was probably the youngest Major in
the UDF). He rose to the rank of Captain at the age
of 21.
Dr Trevor Wadley was an ardent supporter
and active member of the SAIEE.
Two of Dr Wadley's main inventions were the Tellurometer
(the revolutionary radio surveying instrument used worldwide),
and the Wadley receiver (which became the Racal RA 17
high frequency communications receiver and was used
extensively by the British Navy)
(Electron, February 1994)
(Courtesy by
Francois Steyn,
ex editor of South African Dx Magazine ''SADXC '')
TOP
PAGE
|
|
|
I
believe the National HRO500
employes the same scheme as RA-17, Barlow-Wadley, and
the FRG-7. If I recall, one selling point for the BW and
the FRG7 was that by using the same osc any drift cancels
in the two conversions and a mess of crystal references
could be eliminated.
-bob
R.: The HRO-500 used a wadley loop to get the injection
to the first mixer, At first
glance it might appear similar to the wadley loop because
the phase
comparator took it's inputs from the VCO and a crystal
oscillator with
high harmonic contents, in effect locking the VCO to a
harmonic of the
crystal. And you did tune the VCO manually to get it to
the next lock
point. But if the hardware had been up to it at the time
(early sixties), |
the
synthesizer would have looked like what we are used to
now, with a VCO
feeding a divider chain and then the phase comparator.
Radio Shack had a shortwave receiver that used the wadley
loop, though I
can't remember the model number.
And Barlow-Wadley themselves had a transistorized portable
that used the
loop, in the early seventies. Undoubtedly it was alot
cheaper than the Racal, and so perhaps it made the loop
more prominent. I'm still not sure
if it's the wadley loop or the Barlow-wadley loop, and
I think perhaps this confusion comes from the populariztion
of the loop in that portable.
Michael VE2BVW
TOP PAGE
|
|
|
Can
any one help have a Barlow
Wadley Radio in for Service is their a Web site or a Place
in NZ that I can get a Circuit for this Radio?
R.: I seem to recall Rothchilds in Lower Hutt being the
agent way back
whenever, but I could be wrong. If you get stuck, I might
be able to
arrange a photocopy of the circuit diagram from a member
of the NZ Radio
DX League.
Andy Gardner
Chief Editor, NZ DX Times, NZ Radio DX League.
http://navigator.co.nz/nzrdxl
R. 2: Wow that brings back some memories indeed. They
were a very elegant little receiver that converted to
an IF frequency a bit higher that the highest frequency
to be received |
(30
MHz) and then tuned across that band with a double conversion
to get the narrow bandwidth necessary for good shortwave
reception. The up conversion got rid of the usual image
rejection problem so prevalent in the cheaper short wave
receivers.
If I remember
correctly there was a description of the workings of
the wadley loop in a Wireless World during the early
70s I think, or it may have been Electronics Australia!
But the description was good and followed up by construction
articles for the building of such a receiver.
I don't know
if the South African firm is still in business, but
the one that I saw was in Niue of all places in 1978,
when I was crook in hospital with Pneumonia! It provided
me with a good contact with the rest of the world during
that time!
The things that you find in out of the way places!
Regards to you all
John Fulton, Ngaio, Wellington NEW ZEALAND
Phone +64 4 4792043
FAX +64 4 4792043
TOP
PAGE
|
|
|
Can
any one help have a Barlow Wadley
Radio in for Service is their a Web site or a Place in
NZ that I can get a Circuit for this Radio?
I'm not sure
if I still have any info from early WirelessWorld in my
"offsite" archives. IIRC from the age of the
thing it probably used germanium RF transistors like OC170,
which will be near impossible to replace. A bit of ingenuity
should give better longer lasting results with a modern
FET. |
Hamfest
Shopping Guide puts current value US$100 - $200 ...
Southern Cross DX Club in Adelaide list 2 BW rx for loan
to club members so they may have some service info:
http://tolstoi.saccii.net.au/~stephenn/
admin.htm
Peter Kerr bodger
School of Music chandler
University of Auckland New Zealand neo-Luddite
TOP PAGE |
|
|
Hello
everyone, can somebody please point me to the principle
of operation of the Barlow-wadley loop Receivers like
FRG-7 .
Also, I would like to hear about possible Homebrew approches
using this wadley loop design .
R.: As an example, it starts out with
a crystal oscillator, say at 1 MHz. This is fed into
a comb generator, which will generate lots of harmonics
at 1 MHz spacings and is then filtered with a 30 MHz
low pass filter. There is also a VFO. For this example
lets say it runs from 70 to 100 MHz. Lets say there
is also a narrow filter at 70 MHz.
It sounds neat, but there must be some
catch or it would be used more often.
I can think of a couple of possible problems. One is
that the 70 MHz filter, in my example, would have to
be pretty darn good to eliminate the unwanted parts
of the comb signal. The second is that any crud on the
VFO signal will show up on the output, destroying the
nice clean crystal purity.
|
[It is called 'comb generator' because
it looks like the teeth of a comb when you look at it
with a spectrum analyzer.]
The VFO is mixed with the comb generator
and fed to the 70 MHz filter, which filters out all
but one of the harmonics. The output of the 70 MHz filter
is then mixed again with the same VFO signal to bring
it back down to the original frequency (with another
30 MHz low pass filter).
The result is, allegedly, a nice clean
signal that can be switched in 1 MHz
steps by tuning the VFO.Don't give up hope yet. I think
that it still has some use for the homebrewer if you
are aware of the potential problems.
Jim N8EE
TOP PAGE
|
|
|
I
noticed on my BW when I calibrated it that I could not
set the AGC according to the MFR's instructions,
and to understand why I had to re-draw the circuit a little
to make sense out of it. It's a good design, but a little
more confusing due to the positive ground convention.
If the output from the voltage regulator is not EXACTLY
-6.6 volts, then the value that they ask you to set on
TP 5 ( -4.3 volts) is not correct. For example on my BW
the voltage was -6.4 volts, presumably due to small variations
in the reference zener. |
So to set the
AGC properly I think it's best to adjust R28 for 400mV
across R39 ( no signal), and this allows for a range of
outputs from the voltage regulator without confusing the
correct adjustment.
An interesting features of this part of the BW, is that
the AM detector diode is forward biased, this helps detection
of low signal levels. (Click HERE
to see the AGC circuit diagram and author's notes) |
|
|
|
BW
SITE MENU
|
 |
|
|
|
| |
|
