How Many Radio Mics Can You Use At Once
by Andrew Hughes – 10th August 2018, updated 20th April 2022
We’re often asked to supply a large number of radio mics for a single project. When this happens we take the time to explain the licensing limitations, and how we overcome them. Andrew Hughes explains the issues.
A radio mic system comprises one transmitter and one receiver, both tuned to the same frequency. If you use more than one system, each one must be on a unique frequency so that they don’t interfere with each other.
So how many radio mics can you use at once?
The short answer is somewhere between 1 and 20. For more than that you need to apply for extra frequencies from Ofcom. Our personal record is 36 radio mics, running at a central London hotel. As you can imagine, we had to do quite a lot of planning to make it happen!
Frequency planning is tricky, and we’re very careful to ensure that everything works. So we recommend that customers don’t change frequencies without dedicated frequency planning software. For help you can always contact us on the number below. With a large number of systems you may need to use external paddle antennae to reduce the risk of interference.
How to get to 12 systems
Ofcom grants programme-making and special events (PSME) licenses for radio mic use in the UK. With our licence we can safely operate 12 systems on Channel 38 (606.500 to 613.500 MHz). All Sennheiser Channel 38 systems have 12 presets which work well together – this is labelled “Bank 1”.
Here’s how to increase to 20 mics
A few years ago, PMSE licences were modified to allow you to use Channel 65 (823 to 832 MHz) as well. This is also a Europe wide frequency, which comes in handy. For example we have had a few customers who have taken our equipment to trade fairs in France and Germany. You can safely get another 8 microphones onto this frequency band, bringing the total to 20.
So how did you manage 36 radio mics simultaneously?
I can hear you saying “but you’re 16 short”! The answer is that you can apply via the Ofcom website for extra temporary frequencies. You’ll need to know the postcode and address of the location where you want to extra frequencies. Bear in mind that there is a limited number of frequencies available. So for certain locations – Edinburgh during the Fringe Festival – licenses are likely to be booked up very quickly. Some parts of the country have more availability than other parts. There are two things to bear in mind:
- You need to check that you can tune your equipment to the frequencies you are buying.
- It’s vital to check that the frequencies you are buying do not clash or cause interference with any of the Channel 38 or 65 frequencies you are using. You can use the Sennheiser software to check (see below).
How much do extra radio mic licences cost?
Currently (August 2018), an extra indoor licence costs £8.50 per day or £28 per week, with a minimum spend of £28. (Update, April 2022: currently these prices are unchanged)
We check for frequency clashes with the dedicated software from Sennheiser: sennheiser.com/service-support-services-sifm-software
Ofcom provide a handy fees calculator: pmse.ofcom.org.uk/feecalc/radiomiccalc
You can book extra licences through the Ofcom website: pmse.ofcom.org.uk/Pmse/Ecom/loginpage