Problems With Wireless Microphones and How to Fix Them

Because there are so many problems that you can have with a wireless microphone system, I have decided to write an instructable on how to troubleshoot wireless systems.  This can apply to other wireless systems besides microphones, but I will be focusing on microphones, since that is what most of my experience is in.

If I miss anything, or you would like me to add something to this instructable, please let me know.  Also, if you are having problems that are not wireless related, please see my instructable "Audio Problems", or feel free to contact me for help.

Please keep in mind that I can only cover a few problems you can run into with wireless.  I will only cover the basics in this instructable.

This step is taken from my previous instructable "Audio Problems".

Static on a wireless mic is usually caused when the mic is too far away from the receiver, a battery is dieing, or when something is interfering with the signal.  We will cover interference in another step.  Often the simplest way to resolve static is to change the battery, or to get the mic closer to the receiver.

A good way to get the mic closer to the receiver is to move the receivers to an area backstage or onstage.  Many facilities already have wire run from their backstage or onstage areas to their tech booth.  This is generally considered the "correct" way to use a wireless microphone system.

To fix interference on a mic, you need to adjust the frequency on the mic and receiver to another frequency that is not in use.  (Unless you are a licensed operator that is not restricted by Part 15 of the FCC rules and regulations.)  Consult your owners manual for information on how to change the frequency.  You want to change it at least 2 MHz up or down from where you were having interference.  Mostly, you just have to play with it in order to find what the best frequencies are in your area.  You can also use a wireless frequency analysis program, but those are expensive, and require expensive hardware.

Digital microphones use about a tenth of the bandwidth that an analog mic does, but with some of the cheaper digital mics, you can run into problems with a high latency.  (High latency is when there is a noticeable delay between when the person speaks and when the sound system produces the audio... latency is the time it takes for the signal to travel from the source to the destination.)  The reason digital mics have a high latency is that audio is basically analog.  Digital mics have to convert an analog signal into digital, then convert that digital signal into analog.  Not to mention that they will select the channel with the least attenuation.  Granted, this processing takes milliseconds, but add enough milliseconds together, and you will have a noticeable delay.  Most of the major manufactures have fixed this problem in recent years.

Sometimes when you have a microphone that is synced to the receiver via infrared, the microphone will "Magically" change to a different channel, or change a setting.  This doesn't happen often, but it does happen enough to mention.  This is an easy fix, first, find the infrared receiver on the mic (I have mine pictured in this step), then place a small piece of gaff tape over the receiver.  If you need to sync, simply take the gaff tape off and replace when done.

I can't tell you how often I have had actors/musicians/etc. turn off their power switch for whatever reason, and then forget to turn it back on.  Even when you tell them not to!  Here are two ways to fix this problem:

1.  Most microphones have a power lock.  This will keep the mic on, even if it is switched off.  This is the most effective way.  The only way to turn it off is to know how to remove the power lock, or to remove the battery once you turn the power lock on.  Refer to your owner's manual to see if your mic has power lock, and how to turn it on.  Since Shure ULX is one of the most popular mics, I will tell you the process for that one.  Press set, then mode together (set has to be pressed first) until you see Po L on the screen.  It is now power locked.  Generally most mics (including Shure ULX) use the same key-combination in order to unlock that they did to lock.

2.  Place a piece of gaff tape or medical tape over the power switch.  Most people will not remove tape for fear of breaking the mic, and it also protects from accidentally bumping the switch off.

Intermodulation is similar to interference.  Intermodulation happens when you have two microphones or other wireless devices crowding each others frequencies.  The only way to fix this is to change your frequencies to another frequency that is not crowded.  To find frequencies that are not crowded, use an intermodulation analysis program.  One of the best programs available is IAS, however IAS is very expensive.  A free program from Sennheiser is available called "Sennheiser Intermodulation and Frequency Management Software" (AKA SIFM).  It is a very good option if you use Sennheiser microphones, as it already has some of their major models specifications programmed into the software.  You can add other specs in, but you need to know the specs.  I mostly use IAS, so I don't use Sennheiser's software that often, but to the best of my knowledge, you can only use one model at a time with SIFM.

Also, frequency crowding is caused when you are using too many mics at the same time.  Generally, you can only use about 16 analog mics at the same time before you start to have frequency crowding issues, however, if you use a program like IAS, and depending on the area you are located, you should be able to get as many as 22 analog mics.  If you need more than 16 mics, than you should go with a digital system.  As I mentioned before, digital mics only use about a tenth of the bandwidth of analog mics, so you should be able to use about ten times the number mics you could use if you are using analog.

The antennas of a wireless system are the most important part.  If you have a damaged antenna, or the placement of the antennas on your receivers are off, then you are going to have some big problems.  Most wireless body-pack transmitters have a little wire coming out of either the top or the bottom of the pack.  Make sure that this is not being stressed in any way, as that can severely damage the wireless signal.  Also, the antennas on the receiver should be tilted at an 90 degree angle if you are using the antennas that are included with your receivers.  You can also get directional and omi-directional external antennas that will significantly improve your wireless range.  If you are using directional antennas, make sure that you have them at least 5 ft apart and that they are aimed so that they cover the whole area you want to cover.  The best case in scenario would be to have them 10 ft. apart, but that can't always happen.

Any fixed frequency microphone will have an antenna that has a specific length.  You can not change the length, or it will not work well.  If your antenna on a fixed frequency mic goes bad, then you have to get the exact same antenna from the manufacture if you are going to fix it yourself.  Otherwise, get a new mic, or send the mic in for service.

One of the most common problems with wireless systems is signal blockage.  Walls, metal, even the human body can affect signals.  There isn't too much you can do about signal blockage, except trying to move your receivers around trying to find a good spot that is not blocked.  Also, make sure that antennas are not touching a person's skin.  The human body acts as an antenna, absorbing signal.

One of the most effective ways to get good wireless quality is to get the proper wireless system for your needs.  If you are going to install your system permanently, hire an AV consulting company to come in and do a wireless analysis.  This is the best way to determine what microphones will meet your needs, and in the long run it will save you money.  If you are using a portable setup, make sure to over-compensate for problems you may run into.

I have listed my opinion of various wireless companies below.

Shure:
Pros:
Name brand company, almost everyone has heard of Shure.  Their cheaper products are good for some applications.  They have somewhat decent sound quality.  Easy to use interface.  Very good digital products.
Cons:
Products made very cheaply, do not hold up well to professional use.  Their analog systems are prone to wireless interference more so than some other brands.  Will not hold up for a portable system.
Bottom line:
If you are on a budget and don't need a lot of mics, get one of their cheaper products.  Also, their digital products are very good, so if you are going digital, Shure mics might be a good way to go.  Don't buy for portable systems.

AKG:
Pros:
Good sound quality.  Name brand.  Reasonable price.  Very powerful.  Easy to use.  Holds up to wear and tear.  Good for portable systems.  Not bad for installed systems.
Cons:
Most of their products will overpower other brands.  Don't buy if you are mixing cheaper brands.
Bottom line:
The best option in my mind.  Just don't use if you are using a Shure or cheaper mic at the same time.

Sennheiser:
Pros:
Fantastic sound quality.  Name Brand.  Best wireless quality between AKG and Shure.  Easy to use.  Holds up to wear and tear.  Great for all systems.
Cons:
Pricey.
Bottom line:
If you have the money get Sennheisers.

Lectrosonic (thanks to jakdedert for reminding me about this one):
Pros:
Fantastic sound quality.  Name Brand.  Considered to have the best quality of any company.  Easy to use.  Holds up to wear and tear.  Great for any system.
Cons:
Pricey.  Probably the most expensive mic out there.
Bottom line:
These mics are mostly used in video production and for productions with an unlimited budget.  If you can afford a Lectrosonic, then there is no doubt that it is the right mic for you.

Audio Technica:
Pros:
Good mic.  Nice user interface.  Better wireless quality than Shure.  Holds up to professional use.  Decent price.
Cons:
Not as good sound quality as Shure.
Bottom line:
Not a bad mic for those who are on a budget.

Line 6:
Pros:
Decent digital systems for the money.
Cons:
Not as good as Shure for the digital.
Bottom line:
Good entry level digital system.

Nady:
Pros:
None.
Cons:
Terrible wireless mics.
Bottom line:
Don't buy nadys wireless products.

VocoPro:
Pros:
You get lots of mics
Cons:
Very prone to frequency crowding, and there's nothing you can do about it since they are fixed frequency.  Terrible sound quality.
Bottom line:
OK if you don't expect to use all the mics at once and are on an extreme budget.

There are other brands out there, but these are the ones you will see most often.  If you have a question about a specific brand, please feel free to ask me.

Please note that I do claim copyright to the information. I did not use any specific sources when compiling this information, all of this is from my personal experience.

You may quote parts of this information for educational purposes. Under no circumstances will you sell this information.

I do not own the copyright to the of the images in the introduction steps 1-2, and 4-8, however, as far as I have been able to find, I have the right to use it in this instructable. If there is any question about whether or not I have the right to use this image, please contact me. I have no intention of stealing anyone's intellectual property.  I do claim copyright to the image on step 3.

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© 2012