Frequently  Asked  Questions

What is PMR anyway?

PMR stands for Private Mobile Radio. This is the type of radio communication system set up by a company which needs to keep in contact with employees working away from base or head office. Taxi firms, public utilities and security firms are obvious examples of such companies. However, despite the 'Private' part of the name, PMR equipment is also widely used by government organisations such as the emergency services, police and armed forces.

All of the PMR equipment used in the UK operates on specially allocated bands in the VHF and UHF spectrum. There are PMR bands available for use by private companies around 80MHz, 160MHz and 440MHz. Government organisations and public utilities have their own bands at various VHF and UHF frequencies.

What types of PMR equipment are available ?

The equipment used on the PMR bands includes hand portables carried by police and security personnel, mobile sets used in vehicles such as patrol cars, delivery vans and taxis, and base station equipment installed at central locations to communicate with mobile and hand-portable sets.

As radio technology evolves new systems are constantly being introduced, making earlier generations of equipment redundant. Also in recent years many PMR users have had their frequency allocations changed, and have found it more economical to dispose of their existing equipment than to convert it to operate on the new frequencies.

At the moment many firms are in the process of abandoning their existing analogue (FM) PMR set-ups in favour of new digital systems, or just issuing their employees with mobile phone handsets instead.

This is bad news for manufacturers of traditional analogue PMR equipment, but good news for PMR conversion enthusiasts, as much of this redundant equipment finds its way into the amateur market.

What's so special about PMR equipment ?

Commercial PMR users depend on their radio equipment to run their businesses efficiently. Any breakdown of communications is likely to cause a loss of revenue. Government organisations such as the emergency services have equally high demands on their PMR communications equipment, because any failures could have serious consequences.

As a result, PMR users insist that their equipment is manufactured to high specifications in terms of both physical strength and RF performance. This type of equipment has to be robust enough to withstand operation in harsh enviroments with heavy handling by unskilled operators. In terms of RF performance, it has to be able to continue working in areas of high RF field-strength, where less well-designed equipment would suffer interference or fail.

PMR equipment is expensive to manufacture, but it is made to standards and specifications well above the average piece of amateur radio gear.

Why should I convert PMR equipment ?

Building and operating your own amateur radio equipment can bring a lot of enjoyment and satisfaction, not to mention the knowledge and experience you can gain as a result. But these days few amateurs have the time or the technical facilities to make their own equipment from scratch.

Converting an ex-PMR set to amateur use gives you a short cut to the enjoyment, satisfaction and self-training of home construction. You end up with a commercial-grade radio without all the hard work of prototyping, trouble-shooting, metal bashing and pcb construction.

In many conversions all that is required is the replacement of crystals or the synthesiser memory chip, followed by retuning and minor adjustments. And because you become familiar with the 'innards' of your set during the conversion, you will find it easy to add modifications or extra facilities later, if you wish. In contrast, owners of normal Japanese amateur sets are often reluctant to even remove the top cover, especially if the set is still under warranty.

PMR equipment is designed to be robust, functional and efficient, but without any unnecessary frills. So when it is mounted in your car it doesn't look attractive to a casual thief, who is much more likely to be interested in a standard Japanese amateur set (at least it looks like a CB radio!).

Finally, all of us like a bargain, and by converting an ex-PMR set to amateur use you'll get to own and operate a piece of professional radio equipment at a fraction of its original cost. You should be able to buy an ex-PMR set such as the Pye/Philips MX294 and convert it to amateur use for less than £50.

Where can I find ex-PMR equipment ?

Apart from Atlanta Communications, a number of firms offer ex-PMR equipment to the amateur market. Check out our Links Page for more information.

Another good source of ex-PMR equipment is your local amateur radio rally. You can often pick up a bargain here, but it is important to find out exactly what you are buying before you part with cash. This can make the difference between getting a set that can be easily converted to amateur use, and getting an expensive doorstop.

You are likely to pay less if you buy a rig at a rally, but of course there is no guarantee that it will work! Current PMR equipment offered at rallies has sometimes been rejected for one reason or another - perhaps it has that bane of the service engineer's life, an intermittent fault which never occurs while the equipment is under test. Often this type of fault is thought to be too time-consuming and uneconomical to sort out, and the equipment is disposed of. If you have patience and suitable test equipment you may be able to succeed where the professionals have failed in finding and rectifying the fault.

Reputable dealers such as GWM and Atlanta make a point of testing all the surplus equipment they offer for sale. All faulty items are rejected or sold clearly marked 'for spares only'.

What's the best ex-PMR equipment to convert ?

This depends on your technical abilities and knowledge. It's always nice to have a modern-looking set with digital display, lots of memories and flashing LEDs, but this type of set may be full of surface-mount components and custom-programmed processors which are very difficult to modify or replace. So for most amateurs we would recommend PMR equipment built without surface-mount components and micro-processors.

If you will be satisfied with operating on one or two channels eg for a dedicated packet link or for a local repeater monitor, it could be worth looking for a crystal-controlled set. However for normal amateur use you will generally need access to a dozen or more repeater and simplex channels, and in these circumstances a synthesised set will prove cheaper in the long run.

We recommend the Pye/Philips M(X)290-series for general first-time amateur conversion. The M(X)290-series covers a wide range of crystal-controlled and synthesised PMR sets produced from the late 1970's onwards, many thousands of which are still in commercial use. They pre-date the adoption of microprocessor-controlled circuitry, so are suitable for amateur modification and repair. These sets were designed for vehicle installation, but are equally suitable for amateur base use. We expect many Pye/Philips M(X)290-series sets to appear on the surplus market in the next few years.

Why do I need to be able to identify PMR equipment ?

PMR equipment is produced for a wide variety of applications. There are FM (frequency modulation), AM (amplitude modulation) and data modes, and a range of frequency bands from 70MHz to 470MHz. Often a manufacturer uses a common case design for a whole range of PMR sets, and unless you are an expert or a seasoned PMR converter, it can be difficult to distinguish between different sets in the range.

Although it is theoretically possible to convert a 80MHz AM set to operate on 2m FM, why bother? It is much better to find a 140MHz FM set in the first place!

If you are buying the equipment from a reputable dealer or from a knowledgeable friend, you should be able to rely on the information you are given about the set's suitability for conversion to a particular band or mode. But if you are buying from a stranger at a rally or car boot sale, you will need to be able to identify the equipment and come to your own conclusions about it.

Check out the Pye/Philips M(X)290-series General Information page for advice on identifying M(X)290-series sets.

What test equipment is needed for a PMR conversion ?

This depends on the compexity of the modifications required to get the set working on an amateur band.

We recommend the Pye/Philips M(X)290-series because for most conversions there is no need to replace coils and other components on the pcb. In most cases the conversion can be performed by replacing crystals (crystal-controlled sets) or the synthesiser memory chip or PROM (synthesised sets), and then retuning the transmitter and receiver RF stages.

For these conversions there is no requirement for sophisticated test equipment - a multimeter (or a 0-10V reading voltmeter) and a set of RF trimming tools are the only essential items.

A RF power meter and a RF signal generator are useful aids to retuning the transmitter and receiver respectively, but they are by no means essential. If you don't have access to a RF power meter, a VSWR meter with a forward power indicator or a home-constructed RF probe connected to your multimeter will serve the same purpose. If you are short of a signal generator, you can either build a low-power oscillator to act as a signal source, or you can use a consistent off-air signal source eg a local repeater.

A frequency counter can help you to get the crystal or synthesiser frequency exactly right, but if you lack one, you can use another ham set operating on the same band to provide a reference instead.

Other conversions may require the replacement of pcb components and more complex retuning and realignment procedures. These conversions require considerably more RF and constructional ability as well as access to specialised test equipment, and are therefore only really suitable for seasoned PMR converters.

Where can I find more information ?

Our PMR conversion section (PMR Conversion Index) concentrates on the Pye/Philips M(X)290-series at present. We will be adding more information to these pages about other types of PMR equipment when time allows.

We provide modification instructions with all our programmed chips for ex-PMR sets. Check out our Links Page for more PMR conversion information sources.