Radio Mics, can someone introduce me?

[chris999998]

I haven't really used radio mics and this is something my school, where I do sound, is looking to get into; I was wondering if someone could explain - or point me to - the basics of these:

-How does licensing work? Which frequencies need licences?

-UHF or VHF?

 

etc

 

Thanks in advance. :(

[Mr.Si]

Well I ain't good on license info, because I use a rubbish AKG WMS40 (single diversity version) which keeps "dropping out."

 

But at least it is a license free product.

 

Alot of the systems these days don't require a license - Sennheiser offer some good stuff.

 

I think my top piece of advice would be two fold...

 

1. GET UHF

2. GET "True Diversity"

 

 

1.

UHF - Ultra High Frequency

VHF - Very High Frequency

 

With VHF you're likely to get interference from the local taxi services if they pass by etc, because they tend to operate in this band. UHF is probably more likely to give you seemless signal.

 

2.

True diversity is where the receiver unit has 2 Antennae/Arials which have separate circuits and is constantly switching between the two signal circuits depending on which is the strongest. Allowing for (all else being equal) the signal to be continuous and not "drop out".

 

Single Diversity is where there is only 1 Antennae/Arial so this cannot happen and drop outs happen frequently and this gets rather irritating.

 

I think this is all how it is.

 

Other people may correct me if I'm wrong.

 

Good luck in joining this world of wireless.

 

Mr. Si

[Lamplighter]

I haven't really used radio mics and this is something my school, where I do sound, is looking to get into; I was wondering if someone could explain - or point me to - the basics of these:

-How does licensing work? Which frequencies need licences?

-UHF or VHF?

 

etc

 

Thanks in advance.  :(

<{POST_SNAPBACK}>

 

 

Chris

 

Try a google -" radio mic frequencies " for instance.

 

There is a wealth of information at your fingertips!

 

If you are still stuck try a search on Blue Room, then come back with specific questions.

 

Happy searching

 

Brian

[bruce]

If you haven't already done so, read the article by Jim Brown, which was referenced by someone else on a thread late last year. It's very good - worth reading.

 

And also (insert obligatory Luddite quote), don't automatically think that radio mics are the only or best solution for every problem. Remember, they can introduce lots of new problems, and you're using hundreds of pounds worth of equipment to get something that doesn't work as well as a five quid bit of cable....

 

Bruce.

[Peter F]

Alot of the systems these days don't require a license - Sennheiser offer some good stuff.

 

<{POST_SNAPBACK}>

 

I think it would be quite a shock to many people if they were fully aware how many frequencies do require a license.

 

License Exempt VHF frequencies at present are

 

New equipment should use the following frequencies:

173.800 174.000 174.200 174.400 174.600

174.800 175.000

 

Older equipment may continue to use the legacy frequencies:

173.800 174.100 174.500 174.800 175.000

 

UHF Exempt frequencies at present are:

863.000MHz - 865.000MHz

 

That is it, that's your lot. All other frequencies in the UK require a license in one form or another.

 

There are a number of shared frequencies available for which you buy a single license that covers them all and lasts for either a year or 2 years. It's not expensive (£75/year).

 

Now, here is the bit that probably applies to the majority of users here:

 

If you hire a radio mic, on a shared frequency, from a company that has properly licensed it, the hire company are able to provide you with a simple form entitled "Permit to use UHF radio microphones licensed under the wireless telegraphy act 1949". Honestly, it is simple, you only need to fill in your name, address and equipment location.

 

If you have this permit then you can legally use radio mics on the shared frequencies. If you do not then you cannot.

 

There are other, more regulated frequencies available. These are licensed on a per event basis or fixed site basis. They are useful if you need to operate a large number of radios simultaneously or for high profile stuff where you want a more "protected" frequency. You're less prone to interference from the pub next door if you use a more erm... obscure frequency.

 

That's my potted guide to UK radio frequencies, if you want to know more I suggest a visit to www.jfmg.co.uk.

 

All the best,

Peter

[Mr.Si]

That's why I said I couldn't advise on License stuff, because I only have one which is license exempt.

 

What scares me now is that my UHF rad mic system, is sold everywhere as not needing a license and the frequency is 854.900MHz.

 

So does that mean that AKG are wrong? That'd be a scary thing.

[nickb12345]

True diversity is where the receiver unit has 2 Antennae/Arials which have separate circuits and is constantly switching between the two signal circuits depending on which is the strongest. Allowing for (all else being equal) the signal to be continuous and not "drop out".

 

Single Diversity is where there is only 1 Antennae/Arial so this cannot happen and drop outs happen frequently and this gets rather irritating.

 

Actualy thats called 'Diversity Switching' or something like that.

 

IIRC True Diversity is something like having 2 antenna feeding the same reciever. This would be better because the switching can cause delay in the audio and can wear out and cause noise on the feed. Im sure there are other reasons, that I cant think of at the moment.

 

If you can afford it try and get a system where you can move the antenna from the reciever. That way if you find you have problems with the range from FOH to the stage you can (with the aid of some RF cable and a booster) move the antenna closer to the transmitter (on stage).

 

As mentioned above, I recomend reading that guide (it where I learnt most of the above)

 

Regards

 

Nick Baker

[chris999998]

Thanks All, you've been a great help.

 

Cheers,

Chris :)

[paulears]

That's why I said I couldn't advise on License stuff, because I only have one which is license exempt.

 

What scares me now is that my UHF rad mic system, is sold everywhere as not needing a license and the frequency is 854.900MHz.

 

So does that mean that AKG are wrong? That'd be a scary thing.

<{POST_SNAPBACK}>

 

854.9 is a legal shared chanel

 

see http://www.jfmg.co.uk/jfmgecom/jfmg_conten...ter/PIN30_6.pdf

 

page 10

 

jfmg co-ordinate everything on behalf of the government.

[Peter F]

That's why I said I couldn't advise on License stuff, because I only have one which is license exempt.

 

What scares me now is that my UHF rad mic system, is sold everywhere as not needing a license and the frequency is 854.900MHz.

 

So does that mean that AKG are wrong? That'd be a scary thing.

<{POST_SNAPBACK}>

 

It is a legal shared frequency for which you require a license.

This is quite clear if you look at the website www.jfmg.co.uk

 

My original post was intended to highlight the widespread ignorance of frequency regulation in the UK. Clearly, on this occasion, it has served its purpose.

 

If AKG are saying you don't need a license in the UK on 854.900 they are wrong.

 

Handy money saving tip: Buy your license soon, they're going up by 20% this year and possibly the same again next year.

 

All the best,

Peter

[Bobbsy]

A couple of things...

 

First, regarding licencing issues, I've always found the people at JFMG to be extremely helpful and willing to offer good advice. Don't be scared to call them to talk about your needs and/or potential interference problems in your area.

 

Second, for a good background read on RF mics, particularly in a theatre situation, have a look at Kai Harada's notes at: http://harada-sound.com/sound/handbook/rfmics.html

 

Cheers,

 

Bob

[Freddie]

In case you hadn't realised, the Sennheisers we're all raving about are the Evolution Wireless 100,300 & 500

(They are readily available as individual components if you don't like the packages on the website.)

We (My School) bought 2x ew100 lavaliers 1x ew300 handheld and 2x ew100 recievers to replace our old and manky system. Unlike most other radio systems in this price range, they use 2xAA batteries, rather than the more expensive 9V PP3. The ew300 and ew500 transmitters can also be used with rechargeable battery packs, with a nice charging dock.

 

As well as that, they're pretty actor-proof, there's a lock in the software which makes them impossible to turn off without going through the menus, and the batteries and controls aren't immediately obvious if you don't know how to get in (2 butons on the sides) Highly reccomended!!

[Jivemaster]

There's a bit on the Shure site " sureRadioMicGuide.zip " Google will likeley find it. Posting it here would be unfriendly as it is almost a Meg zipped.

[bruce]

On the subject of licensed, unlicensed and "illegal" frequencies....

 

As a matter of interest, realistically what are the consequences of using these frequencies without a license? Obviously there's the risk of crosstalk and interference from an adjacent site which legitimately is using the frequency, but what other risks are there? Has anyone had their wrists slapped? been fined? Had equipment confiscated? been thrown in jail and fed bread and water for a year?

 

Just asking hypothetically of course....licenses aren't expensive, so there's no real reason to avoid getting one!

 

Bruce.

[grandtheftlatte]

this is something my school, where I do sound, is looking to get into

 

On a completely different note, using RF body mics in a school setting is a hundred million times worse than using regular mics. Make sure you actor-proof EVERYTHING. If you can afford the batteries, a good idea is to have actors keep their body mics on at all times, and then just mute the channels from the board. Also, make sure the buttons that change the mic's frequency are always covered, since they will otherwise almost certainly get bumped, and you won't hear the mic.

 

Just my two pence. I've been running sound for a school production for the past ten hours, and I've had to run from the booth to the stage and back at least every other scene to fix something the actors have done.

 

Good luck.