Barlow Wadley XCR-30. Review.
The Barlow -Wadley receiver was made in South Africa in the 1970s. It uses the Wadley drift-cancelling loop principle first used commercially in the Racal RA-17 radio receivers. Dr TL Wadley. The originator, used to work for CSIR , Pretoria, so this radio is very South African.
The set uses BF125 and 225 transistors and may have an IC audio stage, although some designs use a transistor audio amp.
The controls are:
- Tuning – MHz
- Tuning – kHz
- Antenna Trim (Actually preselector tuning)
- Clarify SSB
- Mode USB/AM/LSB
- Signal level meter
- Some sets have fine tuning
Also FM/AM and FM tuning on some sets.
Essentially, this radio is a triple conversion superhet. The first conversion being an up-conversion to a high intermediate frequency. The signal at this point contains frequency drift from the first oscillator. The next conversion is a down conversion from the high IF to a signal between 2 and 3 MHz, which is selected by a further conversion to a normal 455kHz intermediate frequency.
The clever part of this arrangement is that the first conversion oscillator is mixed with the output from a crystal oscillator, and the resulting frequency is used to cancel the drift of the first oscillator. This tuning system eventually lost popularity and gave way to phase-lock loops and then to digital methods.
This all sounds a bit complicated, but for anyone using these radios, it means that tuning is simplified, and that single sideband (SSB) stations can be resolved quite easily. (There are one or two SSB broadcasting stations – most notably AFN on 4319 kHz broadcasting from Diego Garcia).
The radio has two main tuning dials arranged as thumb-wheels. The one on the left is used to select MHz, and the one on the right is used to tune kHz.. Although the tuning capacitors are geared, the dials are not. There is no indication that the MHz tuning is at its best, so you have to tune for maximum noise.
The preselector (Antenna Tuning) can be roughly pre-set and finely tuned later All this sounds like you need three hands, but in practice it is simple and quick. The set has a three position switch for AM, USB and LSB. It has ceramic filters for single sideband reception and fine tuning can be obtained via the “clarify” fine tuning control. The set has a moving coil meter tuning indicator.
Tuning the BBC on 3.255 MHz
1. Set the kHz tuning to 255
2. Set the antenna tuning to around 3 MHz
4. Fine tune the antenna tuning for maximum output.
5. Fine tune the kHz until the station is at maximum output.
This radio was produced in several different versions. Some had an integrated circuit chip in the audio stage and others had a transistor circuit. Some versions of the set had a basic FM tuner.
It seems that there was a sale of these sets in Bree St sometime in the late 70’s. The owner of the set I am about to describe had never had any luck with it and didn’t think much of it. This seems to be the opinion of many people who have had these radios. On the other hand, there were many people who thought these radios were excellent. Certainly, the performance of this set left a lot to be desired and everywhere I looked seemed to have something wrong with it, yet there was nothing wrong with any of the components. The audio quality was very poor so I ordered some spare ICs from the UK. After the second order also failed to reach me, I gave up.
Eventually, desperation set in and I re-soldered every connection on the circuit board. This changed the set from a poor effort into the excellent radio that happy owners had reported. Even the audio worked. The only problem remaining is wear on the “Antenna Trimmer” shaft making the micro-switches a little unreliable. These radios use transistors that are becoming scarce (BF125, BF255), but unless the radio has been connected to an external aerial these should never give trouble. The audio IC is not easy to get and it might be better to make an entirely new audio stage on a daughter board in the unlikely event this gives trouble. If you download the circuit diagram – beware. Although the radio uses NPN transistors, the designer of this set decided to use a positive earth and you have to get your head round this when checking voltages.
The XCR-30 has no hidden complexities, no SMD (surface mount) devices and no CPU chips. This means the set is comparatively straightforward to work on. It uses standard pin-in-hole components. Other radios using the same principle are the Racal RA-17 (and later derivatives), The Yaesu FRG-7 and FRG-7000 and the Drake SSR 1.
This radio outperforms many modern sets, so get it out of the attic and use it!
I just purchased my second BW – this one has an FM tuner and fancy silver front panel. The short-wave radio is as good as ever, but the FM tuner is perhaps not quite as good as a modern one.
1. If the set has been out of use for some time,you may have to replace the battery holder, because most people store things with the batteries left in. I think the set originally worked from “D” size cells, but the power consumption is low enough for it to operate from “C” size. One of my sets works from rechargeable “D” nickel cadmium batteries of 90s vintage.
2. The micro-switches on the antenna circuit are often intermittent. I have noticed that the more you use the set, the better behaved they become.
3. All those stages of amplification make the set very sensitive. It works well on its built-in antenna, but will probably overload with a matched high gain antenna, for which it was not designed. If you are using an external antenna, remember to unplug it when not in use to avoid lightning damage. During one of our highveld storms I had a 6 inch spark jump from the unplugged antenna to one of my sets. How it survived, I will never know.
4. Another set came to me with dry solder joints. Fortunately it was working on FM,so the offending connection was quickly hunted down.
5. My personal view is that the tuning knobs could have done with a reduction drive. Instead, there is a “Clarify” control for fine tuning. Be that as it may, its the radio I use the most.