Barlow Wadley XCR30 Mk2

Details

Date of Manufacture:1973 to 1976

Manuals and schematics :

User Manual: Download Here

Service Manual: Download Here

Tube and Semiconductor Complement:

BF125 , BF255 (12), AC 117, AA12(5), TA611/B

Model Notes

History

The history of this radio is linked to the development of the Racal RA-17, a valve radio designed for the UK Miiltary in the 1950s, which is  described elsewhere in the museum.

According to David  Larsen, who sadly passed away recently:

"It is interesting to note that, in the early 1960s, the Barlow Group acquired S.M.D. Manufacturing Company (Pty) Ltd (SMD), that was located at 9 Young Road in Pinetown,and moved both the staff and the plant to New Germany where it became know as the Barlow Manufacturing Company Ltd (BMC). Barry Cooke, a founder member and senior director of S.M.D. Manufacturing Company (Pty) Ltd, was appointed Managing Director of Barlow Manufacturing Company Ltd." 

Design

The Barlow Wadley covers 0.5 to 31 MHz in 1MHz bands. The set is a triple conversion superheterodyne with intermediate frequencies of 42.5, 2-3 and 0.455 kHz. It uses a Wadley loop to cancel the drift from the first local oscillator, so that the set only drifts off frequency by the amount the second local oscillator drifts. (The second mixer is fed from the product of the first oscillator and amplified 1MHz crystal harmonics). The first two mixer stages use a balanced diode mixer, presumably to assist strong signal handling and reduce spurious responses.

An RF preselector is used ahead of the first mixer. In effect, this has three wavebands: 0-2, 2-7 and 7-30 Mhz. An arrangement of cams and microswitches is used, so that only a single "Antenna Tuning" knob is used.

The set has a product detector for SSB, and the selectivity is selected according to mode. The nominal bandwidth is 3kHz for SSB and 6kHz for AM. The filters have appreciable skirt selectivity, so the AM does not sound muffled.

The audio stage uses a hard-to-find integrated circuit, or a four transistor amplifier. An AC117 is used to stabilise the battery voltage.

The transistor line-up should be regarded as "typical" - you may find other types have been substituted.

Use and Controls

The set is very heavy for a portable radio - it uses  cast parts and a metal chassis to retain the circuit board. 

Controls are:

• MHz tuning
• KHz tuning
• Antenna tuning
• Clarifier (Fine tuning for SSB)
• Calibration knob near 'S' Meter
• Volume / On-Off
• Mode - USB AM LSB
• FM Tuning and FMAM switch on the version with VHF/FM

Tuning is something of a three handed affair involving setting the band, setting the antenna tuning and re-setting it as you scan around each MHz segment. The set is very sensitive - to the point where it WILL overload if you use a good external antenna. Although the RF stages of the set have a reasonably narrow bandwidth - there will be problems if you are situated near a powerful transmitting station. The MHz dial is calibrated every 10kHz.

The tuning issue is something that most users quickly get used to, and for most of us in South Africa, the cross-modulation from nearby transmitters is not a problem. That leaves the problem of spurious responses or 'spurs' . This set is not an RA-17, so there are spurs at every MHz point from the crystal's harmonic generator. The other spurs arise from mixing products within the circuitry, and for the most part can be quickly tuned through. The manual suggests the MHz spurs are useful as a crystal calibrator.("Its not a a bug, its a feature")

These all turn out to be minor issues, leaving a set that is sensitive enough for general use, a bit heavy to take on holiday, but a very enjoyable radio to use with good audio quality. 

One of the best things about this set is that it is economical on batteries. I admit to having batteries over two years old in my receiver. (The other uses rechargeable 'D' cells). The set operates from 6 'D' cells. 

Service Notes

The antenna tuning arrangement can become worn, so that microswitches have to be moved and/or replaced for correct operation.

Some of these sets suffer from dry-joints on the circuit board. The set will present itself as completely or half-dead, or with distorted audio or a combination of symptoms. I couldn't get one set to work until I had re-soldered almost everything.

Re-alignment requires a good deal of patience - squeezing and un-squeezing coils, and the set may become unstable in the process.

Don't be surprised if the transistors used are  different part numbers from the ones in the list.

References

The Barlow Wadley Web-Site (Now defunct) www.barlowwadley.it. You can view it using the "Wayback Machine"

Barlow Wadley XCR30 Mk2 Service Manual