# Wireless mic reciever placement



## garlicfingers (Mar 3, 2013)

I was reading that receivers should not be near your mixer/amp. I moved my wireless receiver near the stage and plugged in into the snake and removed the interference I was getting in all 4 channels. My question is, where do you place your receivers to avoid interference and feedback? I am working in a High School Theatre with a sound/light table at the back of the house.


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## DaveySimps (Mar 3, 2013)

It really depends on how many wireless systems you are using, and the particulars of your entire sound system and venue. Placement of your receivers does not really have any effect on feedback. That is a microphone element / speaker proximity issue. If you are using several wireless systems it is best (in general terms) to use antenna distros designed for your type of wireless systems. Mount these and your receivers in an equipment rack. This helps with reception of each unit. Also VERY important is frequency coordination of which carrier signals your wireless systems are using. The more wireless systems you are using, the increasingly difficult this becomes. This is, perhaps, the single most important item to consider.

In basic terms, the closer your receivers are to the transmitters (within reason) the better your reception will be. There are also special antennas and components that many be used with your receivers that can help you with specific problems you might experience. Most larger touring productions place their wireless rack off stage. I have had great success with housing my rack at my FOH mix position 40' from our stage. Again, many more variables are to be considered.

~Dave

P.S. Welcome to Control Booth! be sure to stop by the New Member Board and introduce yourself. Be sure to use the search function. There are many threads that will be helpful to you as they pertain to your question here.


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## garlicfingers (Mar 3, 2013)

Thanks for your response. We are using 4-6 wireless mics at any given time. They are various brands. I was just reading about frequency co-ordination and syncing your mics. I will try this when I get back to the theatre. We had all of the wireless at the tech table with the mixer and lightboard and we were getting phantom signals and interference. If you turned off the wireless mic pack the speakers would emit loud white noise. Once I placed the receiver onstage all the whitenoise was gone and phantom signals were gone as well.

I will try moving the receiver away from the tech table and see if it helps. If so, I can build a rack to house them all and keep that at the FOH.


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## DaveySimps (Mar 3, 2013)

Since you are using a few different types of wireless systems, you might not want to rack mount them, ultimately. If the aforementioned tips to not cure your problems, post here the make and model of the wireless systems and the zip code you are using them in, and I am happy to see if you are on target with your frequency coordination. 

~Dave


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## NZM (Mar 4, 2013)

What frequencies/bands are your radio systems using? If you are getting "interference" at the receivers with the transmitter off, then you need to identify the source of that RF signal. While its possible it low-level radiation from your other gear, its quite unlikely since all modern equipment has to meet radiation emission standards that would (should) mean it will not cause interference to radio mic receivers in close proximity.

If the source is an external signal such as DTV or other transmission, then you need to check you are using a frequency band that is not prohibited in your area (e.g. 700MHz band in the USA). As already mentioned, frequency management is a very important factor in reliable radio microphone operation. Physical location of the receivers should ideally reasonably close to the transmitters, but they should not be affected by proximity to a mixing console or lighting desk.

In a small venue it is ok to have the receivers at the operator location, but in a larger venue you will probably want to locate them at the side of the stage. At one venue I use regularly for musical theatre performances (seats about 400), I set the receivers next to my mixing position at the rear of the auditorium (perhaps about 50 feet from the front of the stage). At a larger venue I also frequent (1400 seats, with control room over 100 feet from a very large stage) I always position the receivers at the side of the stage. This is when using 25-30 receivers which makes the frequency management quite a challenge.


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## garlicfingers (Mar 4, 2013)

NZM said:


> What frequencies/bands are your radio systems using? If you are getting "interference" at the receivers with the transmitter off, then you need to identify the source of that RF signal. While its possible it low-level radiation from your other gear, its quite unlikely since all modern equipment has to meet radiation emission standards that would (should) mean it will not cause interference to radio mic receivers in close proximity.
> 
> I will investigate the frequencies this week. We have NADY 4 channel wireless mic/receiver sets. 3 of the 4 channels will register signals with no mic packs on. Once I moved the receiver unit to the stage apron I only had signal from the mic pack and I was able to turn it on/off with out the loud white noise from the speakers. I am trying to locate any manuals, but being in a High School I'm luckt to have the cables I need let alone any manuals.
> 
> ...


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## DaveySimps (Mar 4, 2013)

garlicfingers said:


> Is there a meter or device to pickup RF signal and locate it's source?



There is, but they are quite expensive. Kaltman Creations makes their Invisible Waves products. I own them, and they are fantastic, but not cheap. There is always a chance a sound contractor in your area might have them and provide such a service for a reasonable fee. However, you mention that you have the Nady 4 channel single receiver set. They are low end wireless systems, and do not have many features. So, if it is the system I have seen before, you will not be able to retune the carrier frequencies of the systems to help alleviate your problems.

~Dave


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## NZM (Mar 4, 2013)

garlicfingers said:


> Is there a meter or device to pickup RF signal and locate it's source?


Two tools I find very helpful for managing RF with Radio Mics:

1. An inexpensive hand-held RF analyser. I bought the RF Explorer from Seeed Studio. Due to availability, I bought the 2.4GHz base model and added the 240-960MHz module, so its dual band. Cost me less than US200 delivered. It will certainly show you if there is a greater source of RF signal interference in any location. When operating at a new venue, I always have a look at what residual signals are present before turning on any of my transmitters. Here is a link to the model I would have bought if it was available when I was purchasing RF Explorer - ISM Combo [TES03011P] - $175.00 : Seeed Studio Bazaar, Boost ideas, extend the reach . Note they have these RF anaylsers listed under their "Hacking and Measurement" category . My analyser very quickly identified why we regularly had issues with radios close to 660MHz - there is a low-level radio signal right across my city smack-on 660.0MHz. I am not sure of the source, but its there and consistent at around -105dB everywhere I have checked within 30 miles of my home. These analysers were originally made for people flying remote controlled aircraft to find clear channels, but its a very handy low-cost tool for radio mic management too.

There is a cheaper version that just covers the sub 1GHz range http://www.seeedstudio.com/depot/rf-explorer-model-wsub1g-p-922.html?cPath=174.

2. Shure Wireless Workbench is a very valuable software tool for managing the RF spectrum to avoid inter-modulation issues between multiple transmitters. It is obviously good for use with Shure devices, but if you know (or can find) the RF specs for your devices, you can add them and run the analysis for inter-modulation-free operating channels/frequencies. It require a little understanding of radio operations, but there is some good on-line forum support available for beginners. I have used this to identify 30+ "compatible" frequencies for operation of 4 different vendors systems across 3 different frequency bands for one of my regular venues.

Its definitely a good idea to know what frequencies your radio mics are using and be able to adjust channels/frequencies to avoid local interference or to ensure correct operation along side other wireless devices.

_* Note: I have no relationship with the vendor of the equipment noted above other than being a satisfied customer._


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## museav (Mar 5, 2013)

garlicfingers said:


> I was reading that receivers should not be near your mixer/amp. I moved my wireless receiver near the stage and plugged in into the snake and removed the interference I was getting in all 4 channels.


Just wanted to clarify that was likely a result of where the receivers and particularly the antennas are located in relation to the transmitters than a result of moving them away from any mixers and/or amps. And of course one likely compromise is that the board operator can no longer monitor the receivers.


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## pmolsonmus (Sep 19, 2013)

Thought I would post a related question here. I recently discovered that someone at some time installed a wireless mic set up in our high school's press box on the football field. No one with any knowledge was aware that it was there or if a mic was ever used.

I researched the receiver( probably 4-5 yrs old) and discovered I needed a shure slx2 that transmitted 518-542. I picked up a mic. It seemed to work fine while in the press box but I couldn't even get out the door without losing signal. Fresh batteries, group and channel synced no problem. Worked fine until I was 10 ft away - still inside the press box.

I went to get another wireless mic and receiver that I own and had no problem. I was thinking frequency interference from a cell tower or ??? ( there is one a hundred yards away)
Is there something that could cause such a ridiculously short range? Specifically in that range. It synced at 519 .


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## FMEng (Sep 20, 2013)

519 MHz is in TV channel 22. In Milwaukee there is WVCY on that channel. You little mic's 0.03 Watts is competing with 196,000 Watts of television carrier. Try picking a frequency 524-530 MHz. Channel 23 may be vacant. Channels 24 and 25 are used.


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## pmolsonmus (Sep 20, 2013)

Thanks will work on it and update. Luv this site


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