Wireless microphone tips

[Audiodude]

Everybody loves the convenience of cutting the cord and going wireless with your microphones. But getting them to work can sometimes seem like black magic. I put together this handy guide for people who are having problems with their wireless systems. Keep in mind that most microphone problems (wired or wireless) are a direct result of user error. It's imperative to understand how to use a microphone if you want it to work properly.

Wireless dropouts are not usually caused by defective hardware, but by improper use or installation. Before you declare your system defective, make sure you are doing all of these things:

Here are a few "best practices" tips for wireless:

- The most common cause of RF dropouts is improper antenna placement. Line of sight should be maintained between the antennas and the transmitters. If that's not possible in your rack, the antennas should be mounted away from the receivers, possibly up on a wall, balcony rail, ceiling, etc.

- The antenna on the transmitter should not be covered. With handheld mics, take care not to cover the antenna with your hand. If you don't see an antenna, it's probably hidden inside the last couple of inches of the body. Hold the mic closer to its head.

- If you are using a beltpack with an external (wire) antenna, make sure that the antenna isn't wadded up or bent when wearing it. Not only is this bad for the antenna (bend a wire enough times, and it's sure to break), but it severely imparis its transmission. You'll get a lot shorter range and more dropouts with a wadded-up antenna.

- Only use systems that are true diversity (two antennas) and frequency agile (have the ability to change channels if there is interference).

- Signal strength and operating range tend to drop off as the battery dies, so it's generally best to change your batteries at the beginning of every show / service, even if they aren't completely dead.

- Use an antenna combiner if you have more than two wireless systems.

- Use one of the databases provided online by the FCC or wireless mic manufacturers to choose frequencies that won't get interference from licensed transmitters (TV stations, public safety etc) in your area.

- Frequencies of multiple wireless systems must be carefully coordinated to avoid interference with each other. Simply having different frequencies is not enough. Usually, the best way to do this is to use wireless systems from the same manufacturer and series (Shure SLX, or Audio Technica 3000-series, Sennheiser Evolution Wireless, etc.), and use frequencies that are already pre-coordinated not to interfere with each other. If you are mixing systems from different manufacturers or different series, consult an expert.

- True diversity (more than one antenna) is your best defense against dead spots and RF dropouts. In true diversity systems, both antennas must be connected for diversity to be achieved. They should be installed at least 9" apart, and at a 90-degree angle to each other. If they are remote-mounted, the cables connecting them to the receiver or antenna distro MUST be the same length.

- Also remember that human bodies are excellent absorbers of RF energy. Your wireless transmitter probably does not have enough "oomph" to power through an entire audience on their feet. If your antennas are in the back of a room, the middle of the pastor's back may not be the best place for the beltpack transmitter. That forces the signal to pass through the pastor's body on its way to the receiver.

- If you are having problems with clear reception, try reducing the distance between the transmitters and receivers by moving the receivers closer to the stage. If that's not practical, consider remote-mounting the antennas to be closer.

- If one must run long antenna cables, don't scrimp to save money - get the lowest loss cable that's available. RG-8 is recommended. If the cable run exceeds 25 ft, you may need an antenna booster. It's time to call an expert.

There are more, of course, particularly in large systems with a lot of units running at once, antenna distribution units, and remote-mounted antennas. If that's you, you would be wise to consult with a wireless expert (note: the salesman at your local guitar store likely does not qualify as a "wireless expert").

-Jeff B.

[TimmyP1955]

Good advice from Jeff.

I should like to add:

Until one becomes an RF expert (and who wants to go to that much trouble? :-), he should get all of his accessories (antennae, splitters, combiners, etc.) from the manufacturer of his wireless gear. This minimizes the scope for problems, insures that one will get the best support from the manufacturer and dealer, and eliminates the opportunity for buck passing when there is a problem.

If one must run long antenna cables, don't scrimp to save money - get the lowest loss cable that's available.

If one gets all his gear from one manufacturer, frequency coordination is a lot easier. Fire up their coordination software, tell it the city in which it is being used, tell it and what models/frequency ranges are being used, and it will designate which frequencies to use and which to avoid. (Always tell the software that more channels are in use than there actually are, so that there are some alternate frequencies in case of trouble.)

[GZsound]

Here's a wireless question.

Does changing frequencies make reception better? Do you get longer distances between the transmitter and reciever with different channels?

[TimmyP1955]

Depends on whether something is interfering with the original frequency, or whether the original is one that intermodulates with another unit that's in use.

[Audiodude]

In general, the lower the frequency, the better the propagation (the further the operating range, in other words). So a 50 mW transmitter at 300 MHz will have a longer range than a 50 mW transmitter at 900 MHz. However, the difference between two channels on the same wireless microphone system (626.500 MHz and 626.875 MHz, for example) will be negligible. As TimmyP1955 pointed out, the larger concern is whether or not two frequencies being used simultaneously will interfere with each other.

[TimmyP1955]

Darned near every wireless I've encountered (that was in use by a band) came with the transmitter gain set for the best signal to noise ratio, which often means at maximum. As such, with anything other than the most wimpy singer, the transmitter will overload and the sound will suffer as a result. Check your wireless carefully - both by looking at the meters, and by listening with headphones. IME most users fail to notice this.

One some mics the adjustment is a little switch, on others it's a little trim pot. On low cost units it's usually located in the battey compartment. On some of the units that have a digital display on the mic, the gain is accessed via a menu.

[rothwellsmith]

Will the frequency of the wireless mic have any effect on Feedback?

[TimmyP1955]

No. So long as the unit is working correctly, the RF frequency is irrelevant.

[katanne]

wireless microphones are very useful. and alslo, it can give a lot of help to people who are really into music. thanks for the informations that you have provided..=)

[sabianq]

Originally Posted by Audiodude

In general, the lower the frequency, the better the propagation (the further the operating range, in other words). So a 50 mW transmitter at 300 MHz will have a longer range than a 50 mW transmitter at 900 MHz. However, the difference between two channels on the same wireless microphone system (626.500 MHz and 626.875 MHz, for example) will be negligible. As TimmyP1955 pointed out, the larger concern is whether or not two frequencies being used simultaneously will interfere with each other.

700Mhz is beach front property in the radio spectrum.
it blasts through everything. and it is easy to transmit "LOUD"

the reason the TV stations jumped on it when it was available.

a typical antenne tower can broadact as far a 20 miles.
The FCC is only allowing digital information to be transmitted on this band now.

i wan there to be a couple of channels that the general public can play with. like expirmenters..

[sabianq]

Originally Posted by rothwellsmith

Will the frequency of the wireless mic have any effect on Feedback?

keep the gain down if it is roving infront of reinforcement speakers..

the thing i ALWAYS to tell my clients who are going to us the microphone...

i hold the microphone up to my mouth like 2 inches away and replace the "testing... testing grrglr.." with "for anyone who will be using the wireless microphone, please talk into the microphone and try not to set the microphone on the speaker" ...

or something of that nature.... this is very important^^^^^^

people really need to know how to use a microphone if they want it to work properly..

as timmy suggested, i agree..

when i have a singer, (or amyone for that matter) i always turn down the gain of the radio on the handheld unit (that little tiny plastic screw unter the element... sometimes it is a switch that says -10 or 0.. set to minus 10, it is a 10dbu pad.. 0 makes it more sensitive, (easier to clip)..
for the screw type, i always set the microphones to be that same at the hand held. if they are the same model, like a Shure ULX or similar, i use this procedure on all of them. back of the screw all the way to the left CCW(infinity or off) then turn it half way up or half a turn clockwise..

this will make that microphones pretty much the same level wise from the getgo.
then at the recevier, i set all of the outputs to the same about half way, i use a balanced connection from the receiver to the mixer and set the trim on the channels head amplifier so that a microphone signal is avaraging 0db on the meter when the slider is set at the 0db mark...and loud transients like yelling or loud singning is not quite clipping on the meter. a good thump with your thumb on the microphone head should just clip the microphones signal all the way through the system..

[Audiodude]

I borrowed a few ideas from your responses and revised my original post. Thank you to all of you contributed.

[Mr Illusive]

I was doing a big event in London earlier this year and had some drop out issues with wireless mic's. I was confused at first because the aerials were attached and the frequencies of the different mics were'nt clashing. A check later revealed that the two aerials left and right in the back were in fact designed with two different impedances. Unsure as to why they were different but we put the drop outs down to this.