I am going to cover the Licensing side of things here and not go into any kind of comparison between different systems and the way they work as there are many of them out there and I don't use one so couldn't possibly comment on your particular make and model of system!
A bit about me first. I work in the TV Broadcast industry and one of my specialities is spec'ing, licensing, tuning and installing wireless radio mic and in ear monitor equipment for clients. All shows and programmes on TV rely on wireless equipment in some way during their recording/transmission.
All the wireless gear that is available for muso's works on the same frequencies and comes under the same licensing bracket as my work related gear so thought I'd share my knowledge with you all as it seems apparent that a lot of gear is being used unlicensed and therefore possibly illegally.
Here in the UK Ofcom look after it all via the PMSE (Programme Making and Special Events) section. You can look through their website for all of the information and costs, license application forms, etc here: http://licensing.ofcom.org.uk/radiocommunication-licences/pmse/
The frequency spectrum we use is broken up and managed in 8 MHz wide 'Channels'.
For example Channel 38 is between 606 and 614 MHz. Therefore Channel 39 is 614 to 622 MHz, Ch.40 is 622 to 630 MHz, etc.
The good news is that there are some free to use unregulated ranges you can use. There are 2 small windows - one in the VHF range: 173.800 to 175.000 MHz and one in the UHF range (part of Channel 70): 863 to 865 MHz.
There's also the 2400 to 2483.5 MHz (2.4 GHz) range that is free to use and being utilized by many manufactures now.
What this actually means is that they're basically a "free for all" for anyone to use so there is a more likely chance there will be interference issues.
If you use ANY other frequencies outside of the above mentioned ranges then you need to license your equipment for use.
The costs vary depending on the amount of frequencies required, the length of time that they are required for use and the type of license required.
There are 3 license options available, which are:
A) 'Shared' license.
VHF:175 MHz to 210 MHz is available on a 'shared' license basis. There is a group of 15 set frequencies that can be licensed across the whole UK for a year at £75 online or £85 through the office.
UHF: 606 MHz to 614 MHZ (Channel 38) is also available on a 'shared' license basis.
You can tune your equipment anywhere between 606.500 and 613.500 MHz and be licensed across the whole UK.
Since March 2015 this now includes the ranges of 823 - 832 MHz and (excluding Northern Ireland) 1785 - 1805 MHz.
The only disadvantage to the Shared license is that anyone/everyone in the UK can hold one, hence the 'shared' bit. This can increase the chances of interference at a venue, but makes it's a lot less likely than if you were to operate in the unregulated ranges.
The thing to bear in mind is that Comperes, DJs, etc could be on site with their radio mic's in this range. In the real world, and in that instance, you can work out moving frequencies between you to keep everything interference free, it's not too hard to do that.
The costs for this are:
Annually: £75 online/£85 through the office,
Bi-Annually: £135 online/£155 through the office.
B) 'fixed site' license.
You can request specific frequency/s, or be given, a 'clean' one/set for the venue by OFCOM. It lasts a year at a specific venue for a specific frequency or frequencies and the important bit here is that this type of license can only be obtained by the property owner.
This is worth bearing in mind if you do regular gigs at a venue and you're friendly enough with the Landlord to get him/her to book you something to use when you're there. The caveat here is that they will own the license, not you, so they can authorise anyone else to use it as they see fit.
A basic 1 frequency fixed site license is currently £28 annually.
C) 'Coordinated frequency' license.
You can request a specific frequency, or be given, a 'clean' one/set for the venue by OFCOM.
A basic license of 1 frequency at a specified venue for 48 hours (the minimum amount of time licensed) is currently £28.
The heavy bit is that you could be either fined, nicked or have equipment confiscated if you get caught using unlicensed equipment.
These measures, in my experience, are unlikely* but possible so worth remembering.
*Just to add a more recent experience - I was on a job where one particular frequency was in use but had been forgotten about and not booked/licensed. There was an Ofcom representative on site helping someone else out and he had their super-duper portable spectrum analyzer and saw our frequency! After a brief discussion the gist of it was just pay & license it right here, right now and that's it this time but be more careful in the future please!
If you're still with me, congratulations.
I will try and keep this updated and as current as possible.
Any questions the let me have 'em!
EDIT: General update July 2016.
Edited by Noisyjon, 10 July 2016 - 03:34 PM.