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UltraBeat Entertainment
13-10-2009, 09:34 AM
I'm hoping some techie's can help me out on this one.

In theory if i buy 2 sets of Dual wireless microphones (so 4 microphones in total) if there both running on the same VHF channel can i use all 4 microphones using the one receiver?

Solitaire Events Ltd
13-10-2009, 10:16 AM
I'm hoping some techie's can help me out on this one.

In theory if i buy 2 sets of Dual wireless microphones (so 4 microphones in total) if there both running on the same VHF channel can i use all 4 microphones using the one receiver?

I have tried this with UHF radio mics and it didn't work. All it did was to cut out the other mics when they were switched on.

rob1963
13-10-2009, 10:27 AM
This is one of my few technical specialist subjects, as I can answer using my VHF transmitter knowledge & experience from my pirate radio days.

If you have several VHF transmitters (radio mikes) all working on the same frequency, they will basically block each other out, and it's likely that only the one putting out the strongest signal or the one nearest the receiver is likely to be heard. Even then, the signal will still be messed up to some degree by interferance caused by the other mikes.

It's exactly the same as the pirate radio situation in London, with loads of stations right next to each other or on top of each other, resulting in only the strongest one being able to be heard in any particular area, and even then it's often unlistenable due to interferance from the other (albeit weaker) stations.

Sorry Spud, but it's back to the drawing board.

:(

Vectis
13-10-2009, 10:46 AM
Not sure if this'll help at all, but on the Kam UHF dual wireless set I use for Karaoke, there's a "combine" switch, so instead of putting out each mic on a different XLR feed, it puts them out on a single feed.

If this is a common feature (no idea - I've never used anything other than this one unit) then are there 4-way sets out there? Or, by using two duals with 'combine' on, you can at least halve your problem, meaning a simpler mixer arrangement downstream.

spin mobile disco
13-10-2009, 12:35 PM
I dont think UHF has this problem so much as the wavelength is so short but vhf has a longer form. I know I use my kam radio mics on the same frequency sometimes as so many of my venues have other rooms with kam equipment in. A bit like a timeshare for uhf mics.

rob1963
13-10-2009, 12:47 PM
I dont think UHF has this problem so much as the wavelength is so short but vhf has a longer form. I know I use my kam radio mics on the same frequency sometimes as so many of my venues have other rooms with kam equipment in. A bit like a timeshare for uhf mics.

I think this is still a problem with UHF, but it's DEFINATELY a problem with VHF.

VHF uses frequencies which aren't much higher the normal FM radio station frequencies. The FM radio stations use 88-108 MHz, and VHF radio mikes aren't much higher, being around 170 MHz.

However, I think the UHF systems use frequencies around 800-900 MHz, so it's possible things MIGHT be a bit different with frequencies that high, although I'm not so sure.

VHF is what was asked about, and that's the bit I'm certain about.

DJ Jules
13-10-2009, 12:52 PM
Not sure if this'll help at all, but on the Kam UHF dual wireless set I use for Karaoke, there's a "combine" switch, so instead of putting out each mic on a different XLR feed, it puts them out on a single feed.

If this is a common feature (no idea - I've never used anything other than this one unit) then are there 4-way sets out there? Or, by using two duals with 'combine' on, you can at least halve your problem, meaning a simpler mixer arrangement downstream.

Doesn't that just feed the output from the two mic's out the same connector on the back of the receiver though (i.e. it doesn't change the band that the microphones transmit on at all?). Both of the dual channel receivers I've owned (one UHF, one VHF) had separate channel outputs on the back, and a combined one as well so you could either feed each mic individually into a mixer, or just shove both signals into a single channel.

I believe to run four mic's you'll need a pair of reasonable quality dual channel (either UHF or VHF) mic's and receivers with channel switches on both mic's and receivers so you can pick four separate channels (one for each mic) so they don't interfere with each other.

Julian

UltraBeat Entertainment
13-10-2009, 01:02 PM
Thanks Guy's. I knew you would know the answer:)

I didn't think it would work but I've been told by someone it would:confused:

The Mic's i'm using are the double version of these:
http://cgi.ebay.co.uk/Kam-KWM-6-Single-VHF-Wireless-Mic-Kit-_W0QQitemZ110438077510QQcmdZViewItem

Think they have discontinued these units now.

Dynamic Entertainment
13-10-2009, 01:16 PM
KAMs Rackmount twin system allows 2 sets to be used, but you need both recievers still (only 2 units total though in the rack).

That may be your answer. :)

A1DL
13-10-2009, 01:45 PM
You can operate 4 channels of UHF in channel 70 (863.1 to 864.9mhz) without a licence in the UK.

As you may or may not be aware, the licensed PMSE channels (67,68 & 69) are being dergulated in 2012, so unless you can be certain of a return on your investment in just 2 years, I wouldn't advocate buying UHF kit that may not work in the near future. This is the reason the secondhand market is starting to become flooded with secondhand UHF "bargains"

spin mobile disco
13-10-2009, 05:55 PM
I thought they were just discussing the deregulation? Or has it now been approved?

A1DL
13-10-2009, 06:13 PM
I thought they were just discussing the deregulation? Or has it now been approved?

Ofcom confirmed their plans at the end of June, Matthew.
http://www.ispreview.co.uk/story/2009/06/30/ofcom-confirms-clearance-of-800mhz-spectrum-for-mobile-broadband.html

spin mobile disco
13-10-2009, 06:57 PM
Well that screws up about 80% of decent mics on the market what are they going to do for an encore?

DJ Jules
13-10-2009, 07:00 PM
You can operate 4 channels of UHF in channel 70 (863.1 to 864.9mhz) without a licence in the UK.

As you may or may not be aware, the licensed PMSE channels (67,68 & 69) are being dergulated in 2012, so unless you can be certain of a return on your investment in just 2 years, I wouldn't advocate buying UHF kit that may not work in the near future. This is the reason the secondhand market is starting to become flooded with secondhand UHF "bargains"

For those of us who aren't familiar with licensing and terms like "deregulation" - could you summarise in a sentence what that means for the likes of us UHF microphone owners (and what alternatives we're going to have - if any?) 'Cause I ain't got a clue what you just said :)

Julian

A1DL
13-10-2009, 07:09 PM
For those of us who aren't familiar with licensing and terms like "deregulation" - could you summarise in a sentence what that means for the likes of us UHF microphone owners (and what alternatives we're going to have - if any?) 'Cause I ain't got a clue what you just said :)

Julian

Sure :)

I would imagine most people on this forum do not own or use more than four UHF microphones in the same place simultaneously. The budget UHF mics on the market operate across four fixed frequencies in "channel 70" - an area of the spectrum where anyone is free to transmit, without a licence.

If you need to operate more than four UHF mics, or cannot use the four "free" channel 70 frequencies (perhaps because your neighbours are already using them or you cannot risk that) then you need a licence to operate in the regulated spectrum (channel 67,68 & 69). These are the channels affected.

Channel 70 will probably be unaffected therefore disco/karaoke users whom have a couple of budget UHF transmitters today, you shouldn't need to bin them in three years time.

That's it in a nutshell.

Tony

DJ Jules
13-10-2009, 07:13 PM
Sure :)

I would imagine most people on this forum do not own or use more than four UHF microphones in the same place simultaneously. The budget UHF mics on the market operate across four fixed frequencies in "channel 70" - an area of the spectrum where anyone is free to transmit, without a licence.

If you need to operate more than four UHF mics, or cannot use the four "free" channel 70 frequencies (perhaps because your neighbours are already using them or you cannot risk that) then you need a licence to operate in the regulated spectrum (channel 67,68 & 69). These are the channels affected.

Channel 70 will probably be unaffected therefore disco/karaoke users whom have a couple of budget UHF transmitters today, you shouldn't need to bin them in three years time.

That's it in a nutshell.

Tony

Great, thanks Tony - that's really appreciated...






...and it makes me really glad I bought a Sennheiser Freeport (4 channel) a few months ago, and not the 16 channel Kam ;)

Incidentally, how do they police unauthorised use of the UHF bands?

Julian