Wireless Microphones

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tomfassett

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This topic was "expanding" in a radio specific thread so I thought I would post a generic version for those of you who are not fortunate enough to own a PRO106... ;- )

A set of frequencies I have always monitored is wireless microphones. I worked in the AV business most of my life and I always kept a scanner in my workbox. It was a great way of troubleshooting a wireless microhone system to see if the transmitter was working when there was no audio coming out of the reciever. One thing most people who use wireless microphones don't realize is that when the audio is muted on the console, that transmitter pack on their hip or in the handheld unit is still transmitting. That is how a lot of "oops" moments show up on the local news. Someone leans over and whispers something in the ear of an associate assuming nobody else can hear because the engineer has the channel muted on the main sound system. Most don't realize that there may be a media person with a scanner connected to a recorder in the audience or in the broadcast truck. Whenever I was dealing with a political or celebrity type client, I always warned them about this and turned off their belt pack until they were ready to step on the stage and give their speech.
Wireless microphones are everywhere nowadays--local churches, civic clubs, remote broadcasting (media), product demonstations, concerts, weddings, etc. You can find the frequencies by going to the websites of the manufacturers where they post the specifications on their products. The newer more expensive ones have gone all digital but there are millions of the older FM types out there.
A few months ago I was sitting on downtown Phoenix near all the big hotels (waiting for a contractor to show up) and I picked up no less than 13 different transmissions in a space of around 10 minutes. Most of them were idle chatter before or after speeches in the ballrooms.
Many years ago I was listenning to the wireless transmissions of a travelling "preacher." Off the stage his language was worse than I heard when I worked on the trucking docks. That's just one of the many interesting experiences I've had listenning to wireless microphones.. ;- )

I no longer have a list of the specific frequencies as the last time I used the things they were in the 159 MHz range for the "cheapies" and the 400-500 Mhz range for the expensive models. Now they go all the way up to the 1.3 - 1.5 GHz range. I would guess that there are still millions of the things out there in the VHF and UHF range. Most of the manufacturers have the frequency specs on their websites. Many of the better systems are "frequency agile" now, meaning that they can be programmed to any one of a number of different channels. These channels still fall within the frequency lists that the manufacturer is licensed for.

Some of the more popular brands when I worked with them were:
Sennheiser
Vega
Sony
Shure
AKG
Samson
Panasonic
And a host of smaller manufacturers. If you want to know who makes wireless microphones, google the subject and go to their websites. There are also a lot of AV forums and sites which have frequency lists since it is always a good idea to know what you might run into (for cross talk purposes) "out on the road."

Tom F
 

K4IHS

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I worked the sound board at a local theater for many years. The actors used head worn mics with an under clothes transmitter pack and were always forgetting to turn them on. So we just left them on all the time and I muted individual users at the sound board when they where off stage. Of course I could still hear them in my earphones. I never knew what I was going to hear next like the pair getting a little action in the storeroom between acts! :)
 

jfhtm350

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I picked up a church sermon this morning on 171.8750. There is a Church about a mile from here but I wouldnt think a wireless mic would travel that far would it. Maybe someone just decided to broadcast it.

The Cordless Microphones Wiki link doesnt work.
 

tomfassett

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You would be surprised how far those lower frequencies can travel. A scanner is way more sensistive than the average wireless mocrophone reciever which is limited on purpose to reduce cross talk from nearby transmitters. I used to run sound at a church as well and if I was running late I would turn on the wireless mic channels on my scanner when I was a half a mile away to make sure my assistant had given the minister his microphone and turned it on. Of course, this can backfire on a person as once I heard the minister complaining about me being late and suggesting maybe they should get another audio person. Problem was, they couldn't--I owned the entire A/V system... ;- )
There are three churches within a mile of my house that use wireless microphones and with the antenna on my roof, I can pick them all up clearly. I can also hear the McDonalds, Jack in the Box, Del Taco and Burger King drive thrus as well. So at least I'm set for food and religion... ;- )

Tom F
 

jfhtm350

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Is that a normal frequency for wireless mics (171.8750)? It did kind of sound like I was picking up someones tv being on or something but that could have just been the sound of it I guess. Ill be looking for it again next Sunday and Ill see maybe where its coming from. I have picked up Burger Kings mic from all the way across town so I guess they can have a long range like you say.
 

noaim

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Do mica have a way of telling which frequencies they are if you have physical access to them?


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tomfassett

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Is that a normal frequency for wireless mics (171.8750)? It did kind of sound like I was picking up someone's tv being on or something but that could have just been the sound of it I guess. Ill be looking for it again next Sunday and Ill see maybe where its coming from. I have picked up Burger Kings mic from all the way across town so I guess they can have a long range like you say.

That is in a fairly standard range for wireless microphones (especially older ones). I had a Shure wireless (an L8) that was in the 169.000 MHz range.
Most wireless microphone receivers have the frequency listed on a tab or sticker on the back. This is essential if you have a bunch of them and have to match them to their transmitters. We had racks of the things at the AV companies I worked for and God help you if you sent out the wrong beltpack or handheld with a receiver.

With my roof antenna I can pick up Burger King clear as a bell and it is almost 2 miles away. I can see the Jack in the Box from my roof but since there is a big old tree between the antenna and the restaurant, it doesn't come is as clear. It is interesting to listen to the background "chatter" before the control box kicks in the audio. The repeater is often still transmitting even when the clerk hasn't keyed the mic or switched to the drive through on the beltpack (many have an internal talk channel as well for talking to others who have on beltpacks or to the speaker in the kitchen). People in the drive through also seem to think that nobody can hear them until the clerk comes on and asks for their order. A couple weeks ago I heard a mother screaming at her kids so hard it made the hair on the back of my neck stand up (and using atrocious language inappropriate for talking to a kid). When the order taker came on, her voice switched to the sweetest, most sugary disposition you ever heard. As soon as the order taker told her to pull up to the window, the evil witch persona came right back... ;- )

Tom F
 
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ecps92

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Usually , single channel units will have the freq listed on the bottom/back right next to the FCC ID, the others would [multi channel] be in the manual.

Best One is the 169.4450 right next to 169.4500 CBP :)

I know if you have the fcc id number you can look it up and it will tell you what frequencies it uses.
 

k8tmk

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Our Vegas are in the 700 MHz range.

Our VocoPros are in the 629-694 MHz range.

Our Audio-Technicas are on 541.500 MHz and 655.500 MHz.

We also have some new ones made by Shure, but I don't know what frequency they are.

In total, we have about 14 wireless handheld and lapel mikes.

We had to get some of them rebanded due to FCC regualtions. The ones that were rebanded don't have anywhere near the range they had before rebanding. We even had to move the receivers toward the front of the sanctuary to cover the chancel (our sanctuary is only 70 feet front-to-back!).

Randy
 

datainmotion

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Wirelessly posted (Clacking rocks together: Mozilla/5.0 (Linux; U; Android 2.3.4; en-us; DROID X2 Build/4.5.1A-DTN-150-30) AppleWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1)

Some of the first generation Panasonic Arbitrator in-car video systems used the 600-700 MHz part of the spectrum for the officers belt mic. Other older systems used VHF freqs more traditionally associated with wireless mics and most current systems use 900 MHz or 2.4GHz, some analog, some digital spread spectrum.
 

tomfassett

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Considering the number of wireless systems that used to be in the "forbidden" frequency range, I'll bet there are tens of thousands of them out there still in operation. The pro units like Sennheiser and Vega mics generally belonged to large AV companies that would know they needed to be rebanded. Even then, as the pro units got older, a lot of companies sold them off (I know the ones I worked for did). The local 300 member church where one of the ushers comes in early to turn on the mic and stick in a fresh battery probably has no idea. Fortunately, they have a limited range. Unfortunately, they are everywhere and some of them are 30-40 years old and still going strong.

Another use of wireless mics that I failed to mention is musicians. That guy with his little "boom box" amp playing guitar out on the sidewalk in just about every town in the nation probably has a wireless mic. Tempe, AZ has a big downtown festival every year. We used to hate it because we provided systems to Arizona State University as well as the main entertainment stages. When we fired up the wireless systems, we would get cross talk from everywhere (as well as rf harmonic crosstalk and distortion). We had to take a lot of spares, even with the frequency agile systems... ;- )

Tom F
 

newsphotog

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IIRC correctly, a lot of the newer wireless mics are digital but I haven't messed around with sound lately enough to say that with certainty.

I worked the sound board at a local theater for many years. The actors used head worn mics with an under clothes transmitter pack and were always forgetting to turn them on. So we just left them on all the time and I muted individual users at the sound board when they where off stage. Of course I could still hear them in my earphones. I never knew what I was going to hear next like the pair getting a little action in the storeroom between acts! :)

Haha, I've been there before...
 

tomfassett

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I thought I was the only one who did that... ;- ) Actually, I know better. Every audio engineer I worked with had a story like the one K4IHS told. That one would have ranked high on the "retelling" list... ;- )
 
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