AKC's affordable WMS300 UHF Radio Mic System allows no less than eight microphones to be run simultaneously. Our inquisitive Editor Paul White gets to grips with it.

Not so long ago, a reasonable radio mic system was prohibitively expensive; the alternatives were pretty useless and quite probably illegal too. A respectable VHF system costs little more than a good wired mic now, which is great news if you just need two or three radio mics to spice up your act for small venues. If you're playing larger gigs and need more than three or four mics on stage at once, however, you need to think about UHF.

Traditionally, UHF is very expensive — up to ten times or more the cost of a budget VHF system in fact. UHF does, however, offer advantages over VHF: more channels can be run simultaneously; immunity to radio frequency interference is significantly better, especially in crowded suburban areas; lastly as the antennae are very short, they don't interfere with clothing when bodypacks are being used. Of course, there has to be a negative side to any story, and in the case of UHF, you have to pay for a licence to use it whereas approved VHF systems operating on deregulated frequencies require no licence (see box 'Licensing').

THE SYSTEM

A professional UHF system, AKG's WMS300 isn't cheap, but it is around half the cost you'd normally expect to pay for such a package. A maximum of eight microphones can be run simultaneously without running into intermodulation problems (something which VHF can't provide), and each microphone can be switched to work on one of 16 frequencies.

To maintain maximum flexibility, the WMS300 is available with ten different front end variations; the hand-held version can be fitted with any one of three mic heads; there are six headset and Lavalier options for use with the bodypack transmitter, plus a guitar/instrument input.

AKG have tackled another perennial radio mic problem — battery life. There is no avoiding the fact that you're going to get through a lot of batteries, and most systems will use a set of batteries per show. The WMS300, however, incorporates low power circuitry where possible, which means that up to 12 hours of operation can be attained from a set of alkaline batteries. Rechargeable batteries can be used but are not recommended for long sessions — as they suffer from a memory effect when recharging, you can never be sure how long they're actually going to last. Nicads, properly charged and in good condition, should last around four hours.

A half width, 1U package with removable antenna, the SR300 receiver is a true diversity model, with switchable receiving frequencies. It is powered from an external mains adaptor, but for more sophisticated applications, it can be connected to a remote diversity antenna system.

Cheaper diversity systems use a switching matrix to select the strongest signal from one of two antennae. A true diversity system, however, has two separate receivers in the same box, each fed from its own antenna. A seamless switching system continually selects the receiver with the best signal-to-noise ratio.

THE TRANSMITTERS

The hand-held mic transmitter, which is quite chunky but reasonably light with a stub antenna, is powered by three AA alkaline cells that fit inside the handle. Changing the batteries is very simple and involves unscrewing the bottom half of the body to reveal the battery compartment, inside which you'll also find four DIP switches for selecting one of the 16 operating frequencies. On the body of the mic is a 4-position sensitivity slide switch, an on/off switch for the mic, and the power switch for the transmitter. Red and green status LEDs are located just above the sensitivity switch: red denotes a problem with phase lock or low batteries and green indicates when the mic is functioning correctly. The red light also flashes on signal peaks to act as a peak warning indicator. If both LEDs are off, the batteries are dead or the unit is switched off.

The capsules come straight from the Tri-Power series of wired mics and include the D3700WL300 dynamic cardioid head and the D3800WL300 dynamic hypercardioid head. Changing the head is simply a matter of loosening the blue locking ring, unplugging the head, then lining up the internal connectors, and plugging in the new one.

"... a serious system at a seriously appealing price..."

The bodypack transmitter can be used with dynamic or capacitor headsets or Lavalier mics as well as with a guitar cable. Despite its all metal construction, the unit is very slim and reasonably light. A simple coin-in-the-slot screw secures the battery compartment, again taking three AA alkaline batteries. The transmission frequency is set using a miniature rotary 16-way switch, accessible using the supplied screwdriver. Like the hand-held unit, there's a sensitivity control and a pair of red and green status LEDs, but as these will be hidden in normal use, they're only really useful for setting up. A recessed power switch sits alongside a three-way slide switch for selecting mute, mic or line operation. A flexible antenna around 80mm long protrudes from the top of the unit, and a sturdy wire clip provides secure belt or trouser top fixing.

THE RECEIVING END

The compact SR300 receiver comes complete with two BNC connection stub antennae. These work fine in applications where the transmitter/receiver distance isn't too great. However, the distance shouldn't be allowed to fall below three metres or so, just in case the transmitter overloads the RE input stage on the receiver.

If remote antenna mounting is required, up to 20 metres of RE cable may be connected between the antenna and the receiver. More satisfactory operation is offered by the RA300B booster (two required) and the PS300 wide-range antenna splitter which permits the use of greater cable lengths. The latter also enables up to eight receivers to be fed from one pair of antennae. The audio output is available on a balanced XLR and on an unbalanced jack.

Once the receiver is set to the same channel as the transmitter using the front panel rotary dial, it really is a matter of plug in and play. As well as showing the RE signal strength and the AF signal level, status LEDs also indicate whether diversity receiver A or B is handling the signal. If the signal mutes because it is weak, a red LED comes on. A variable squelch control is provided to automatically mute the signal in the event of the received signal becoming so weak that excessive noise is likely. The best way to set up this squelch control is to switch off the transmitter, then increase the squelch level until background hiss is just eliminated.

IN USE

The hand-held system works extremely well from a technical viewpoint. Added benefit is provided because the mic isn't unduly heavy and feels well balanced. All three mic heads are excellent performers, and for guitar operation, all that's needed is the bodypack receiver and the jack instrument lead that comes with it. The audio connector on the bodypack is a locking 3.5mm mini jack, although other options are available.

All radio mics use some form of compander system to keep the background hiss to a minimum. This works by compressing the signal at the mic end, then expanding it back to its original dynamic range at the receiver end — it's a bit like dbx tape noise reduction if you've ever come across that. The use of a compander makes a huge difference to the perceived signal quality, but when the signal level is very low, you may occasionally hear the background noise increasing slightly during the signal, then falling back to silence during pauses — this is quite normal. If the sensitivity controls are set so that you're getting as much level as possible without making the clip LED come on too often, you should rarely, if ever, hear it. I did some tests using the bodypack transmitter with an acoustic guitar fitted with a pick-up, and only by setting the transmitter sensitivity very low and by playing extremely quietly could I hear any 'noise breathing'. In this respect, the system performed really well, and the resulting guitar sound was gratifyingly bright and natural.

CONCLUSIONS

If you only play weekend gigs at the Slug and Lettuce, then a VHF system will cost you less than twice the price of the annual licence for a UHF system. The odd spot of taxi breakthrough will probably get a bit of a laugh rather than having people asking for their money back. On the other hand, hard working professionals need to be confident that taxis and radio hams won't be joining in on the choruses, and they often need more than three radio mics on the go at any one time. UHF will enable you to use four or five mics maximum per band, and you can buy a licence for each band if you need to use both at once. In this case, UHF is the safest option. With a deregulated VHF system, four mics at once is the absolute best you can hope for, with three being a more realistic figure. More VHF channels can be obtained by mixing regulated and deregulated frequencies, but then you're back to paying for licences, and you still have the problem of interference to worry about. Using the WMS300 UHF system, you can have up to eight mics on the go simultaneously — if you use both bands.

If you fall into the category of needing a UHF system, the AKG WMS300 is the only one I can think of that comes in at less than a grand per channel. It can certainly stand up to life on the road too as Prodigy have been discovering on their recent tour (watch out for a feature). Although the WMS300 system undercuts its competitors on cost, it is nonetheless a decent performer. Some compromises may have been made on the packaging to keep manufacturing costs low, but the circuitry and standard of construction is designed to meet the needs of professionals who depend on equipment like this day in, day out. This is a serious system at a seriously appealing price, well supported by a range of useful accessories, optional mic heads, and a wide-range antenna splitter.

WMS300 systems from £940 inc VAT.

AKG, Harman Audio, (Contact Details).