Planning for the Future
It can be helpful if you can have all your systems operating in the same frequency band (VHF, UHF etc), because you may be able to interchange antennas, antenna distribution systems, and other accessories. However in a large complex system with several local TV channels in the area, you may simply not be able to achieve this.

While you do not have to necessarily stick with the same manufacturer, or the same series from a particular manufacturer, to manage frequencies successfully, it is a fact that if you choose all your systems from the same manufacturer’s series, the system can, to a greater or lesser extent, aid with frequency compatibility issues. Manufacturers may give you a list of coordinated frequency groups that have been calculated to work together. If you are obliged to go outside a group, then you need to use a calculator, such as the one referred to earlier, to find frequencies that will work together successfully.

This kind of planning can be made a lot easier with the most modern systems, which, when linked together, can scan for usable frequencies. However, only a few, including A-T’s 4000 and 5000 Series, can actually choose frequencies that also bear in mind the requirements for avoiding third-order intermodulation problems.

Keep a list of the existing frequencies you are using so they can be quickly referenced for frequency planning as the system is expanded. Knowing your frequencies can also be a great help when something unexpected happens. For example, you might have two systems in use that work fine together, and then one day the band has a new guitarist and she brings her own wireless system with her, switches on and everything goes haywire.

Having some means of finding a set of workable frequencies — and a frequency agile system — will be extremely helpful here. However, it is worth noting that it is not necessarily a good idea to choose a system entirely based on the number of frequencies it can operate on.

Frequency Spacing
There needs to be sufficient space between the available frequencies to get a signal through, and subdividing that space into a large number of individual frequencies sounds impressive but may not really help, as it’s the number of usable channels that matters. It’s like having a car with a thousand gears: it sounds very impressive but it’s really more trouble than it’s worth.

In addition to having the tools to deal with frequency allocation issues, you may wish to delegate someone to manage your frequency allocation, and make this known to your staff, so that anyone new coming into the building with their own wireless can be sent to your sound engineer or frequency coordinator to get their system appropriately integrated into the house system.

It’s one thing to suddenly add, for example, rented systems for a pageant or other special event, but it is another to add wireless systems as part of an overall plan over a period of time. Here frequency planning and the allocation of bands can be particularly helpful, enabling you to add systems over time and know that they will work together in several different configurations as required.

Where can you put it? Once you have a number of wireless systems, you will eventually find that becomes difficult to line up the receivers on top of the mixing console while keeping the setup neat and tidy. You may want to rackmount the receivers in a different room, for example, and use remote antennas with antenna distribution systems.

Typically four receivers can be served by two antennas using such systems, thus cleaning up the installation. But it is very important to use the right type of cable and accessories when doing this.

You cannot use regular TV coax cable or cable-TV splitters for example: they exhibit a great deal of loss, which can reduce your usable range dramatically and produce other problems. A cable-TV splitter might cost $5, but a proper wireless system antenna splitter may cost $400. Many splitters can also be cascaded (within the same frequency band) so that you still only need two antennas even if you double the number of systems.

The correct antennas and accessories together form a complete system that will maintain the maximum performance from your setup.

Bearing these considerations in mind will hopefully help you to expand your wireless system painlessly and effectively.

Bob Green is Product Manager, Wireless & Circuitry Products for Audio-Technica U.S., Inc.