Wireless Wireless Microphone FAQ (READ ME FIRST!)

mbenonis

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First, if you are having trouble with your wireless mics, answering the following questions in your initial post will help us solve your problem quicker.

- What problem are you seeing? Is it dropout, interference, completely nonfunctional, etc?
- How many systems are you using?
- What make and model are your systems (could be multiple)
- What band-split do the systems operate in (could be multiple)
- What frequencies (channels) are each mic set to? Are these frequencies coordinated using software (see the FAQ in a separate thread)?
- Where are the receivers located in the facility?
- Where are the receiver antennas located?
- Are you using any kind of antenna split/distribution system?
- Do you have any other wireless devices in the area (TV-band, so things like wireless intercom, IFB/In-Ear Monitors, etc. NOT Wi-Fi, this won't affect mics).
- What is your zip code? (if in the USA)
- What solution(s) have you tried already? Did it help, hurt, or do nothing?
- Do you have your manual around?

Second, I've decided to post a list of frequently asked questions relating to the RF side of wireless microphones, digital TV, the 700 MHz auctions, and related issues. It will be geared toward the United States, but I will try to research other countries' laws if it is requested.

The FAQ is very much a work in progress, and I will be updating it regularly. Please feel free to post additional questions, and I'll try to answer them and add them to this FAQ.

New May 20, 2008:
I've added the tutorial to my website, and to keep things simple (so I don't have to update both places every time I change it).

New September 8th, 2008:
Added information about 900 MHz wireless mics (DON'T BUY THEM!) and the NPRM for the 700 MHz spectrum.

New November 7, 2008:
Updated to reflect the reality of White Space Devices.

New February 9, 2009:
Updated to reflect DTV delay.

New September 18, 2009:
Minor content modifications and a new URL.

New January 16, 2010:
Updated to reflect new FCC rules with respect to wireless mics.

New December 24, 2010:
Updated to reflect new TV Band rules released in September. Also made minor clarifications and typographical fixes.

New November 27, 2018:
Updated to tweak wording.

Last Updated: November 27, 2018.

http://www.benonis.net/wireless-mic-faq/

Also: Do Antenna Distros Prevent Intermod?
 
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Chris15

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Mike, I'm noticing an absence of mention to Wireless Workbench which from memory also will do the intermod calculations for one... As well as then updating the freqs on UHF-R or U series receivers upon direction. This after you connect an omni antenna and let it do a spectrum sweep...
 

mbenonis

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Mike, I'm noticing an absence of mention to Wireless Workbench which from memory also will do the intermod calculations for one... As well as then updating the freqs on UHF-R or U series receivers upon direction. This after you connect an omni antenna and let it do a spectrum sweep...
I don't have any UHF-R systems, but I'll take a look into it.
 

mbenonis

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I just updated the FAQ with a few new things.
 

mbenonis

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I didn't even see the chart. I do feel obligated to point out one error on the chart though. The 902-928 and 2400-2450 bands are actually allocated to the Amateur Radio Service in the US, and licensed amateurs have priority over unlicensed devices (Wi-Fi, cordless phones, etc).
 

museav

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A detail I have had pointed out to me is that at least up until now, the auctions of the 698MHz and above frequencies do not specifically require that devices like wireless mics cease operation in those bands, other than perhaps the public safety bands. There may be problems if you interfere with the licensed users in those bands but there may also be a lot of this bandwidth that is not used, at least for some time and especially in rural areas.

For example, I believe the Qualcomm bought the Channel 52 (698MHz to 704MHz) rights nationwide for their MediaFLO mobile TV service, but that may not be active in many geographic areas and apparently nothing would prevent you from using those frequencies as long as that use does not interfere with the licensed user. Some other bandwidth rights are being purchased for future technologies and may be open for some unknown time.

So I don't think that wireless mics operating at 698MHz and above will necessarily have to stop being used. I believe they will stop being sold and their use may be limited if the bandwidth is used in that area, but at least for now (or until the relevant laws change), for some people there may apparently be nothing preventing their use.
 

mbenonis

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A detail I have had pointed out to me is that at least up until now, the auctions of the 698MHz and above frequencies do not specifically require that devices like wireless mics cease operation in those bands, other than perhaps the public safety bands.
Unfortunately, things aren't quite that clear. The sticking point is that wireless microphones are not Part 15 devices in the US, but rather Part 74 devices. Part 74 devices, defined in 47 CFR 74.800, may only operate on unused television channels. After February 2009, the spectrum from 698-806 MHz will no longer be allocated to television - so part 74 no longer applies. So the bottom line is, while you probably won't get caught immediately for operating there, you can't legally operate the device there - licensed or not (a whole other issue).
 

museav

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So the bottom line is, while you probably won't get caught immediately for operating there, you can't legally operate the device there - licensed or not (a whole other issue).
Which doesn't really change anything for the probably 90%+ of the total number of wireless mic users who are technically already operating illegally.

Here's the response I received last Saturday from a very knowledgeable individual when I made basically the same comment that you would not be able to use wireless mics in the "700MHz" bands after February, 2009 on another forum:
Not necessarily: as of the October 2007 revision to Part 74 and last Wednesday's FCC release of Amendment of Parts 1, 2, 25, 73, 74, 90 and 97 of the Commission's Rules to Make Non-Substantive Editorial Revisions to the Table of Frequency Allocations and to Various Service Rules still have BAS devices permitted to operate in channels 52-69.
As I understand it, the FCC has stated an intent to prohibit continued operation of Part 74 BAS devices, and specifically wireless mics, in the 700MHz bands but have not yet actually revised the rules to reflect this. I'm not arguing, more just agreeing on how unclear some of this still is.
 

mbenonis

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I definitely agree that this is a very gray area in the industry. However, I still believe that it would be extremely poor engineering practice, as well as simply irresponsible, to knowingly operate a wireless mic (or IFB) system after the cutoff above 698 MHz, legal or not.

Would you mind posting a link to the other forum you mentioned?
 

museav

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That particular comment came from Henry Cohen (http://livedesignonline.com/broadwaymasterclasses/sound/henry_cohen_broadway_sound_master_classes/) in the ProSoundWeb (PSW) Church Sound forum in a thread that started when someone posted that their music store salesman told them that their local TV station would be "taking the VHF frequencies", apparently all of them since he expected problems with any VHF mics, when it went digital. Hey, it was the music store guy. ;-)

Henry posts a lot on PSW and a number of other theatre and audio/RF related forums and is very well informed on RF related issues. You two would probably have some interesting conversations as you both seem to know a lot of the details on this.
 

mbenonis

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Ah yes, Henry. While I don't know him personally, we have conversed a few times on the theatre sound list-serv. I'll be attending his presentation at the Broadway Master Sound Class this May, and I hope to talk to him in detail about these issues after the presentation.
 

BBabb131

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May 23, 2008
Good Friday morning.
I'm confused as to the info available about whitespace frequencies, wirelessmics and HDTV broadcast. I have spoken to several mic company reps and cannot easily make headsor tales out of what they are saying.
Any input is appreciated.
 

mbenonis

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Please read over the FAQ, and then ask any and all questions that you still have (even if it seems dumb - I'm sure lots of other people are thinking the same question!). I will admit this is a very confusing topic, and I'd like to make the FAQ as clear as possible.
 

mbenonis

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I've updated the FAQ with regard to 900 MHz mics (DON'T BUY THEM!) and new information regarding the 700 MHz spectrum. Please take a look!
 

museav

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Mike,

I believe the 700MHz ban is currently proposed by the FCC and open for comment, but is not yet enacted. It almost certainly will be, however as of right now there is no actual prohibition, only a proposal for it. Yes it is a detail, but there are already too many common misunderstandings of what is conjecture or proposed versus what is law so it seems important to be correct on the distnction.
 

mbenonis

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Brad,
You are of course correct. That said, I think it is important to emphasize that while it is currently legal to use 700 MHz devices (only with a license, of course, and we don't qualify anyway), it is very likely that it will not after February 17, 2009.
 

waynehoskins

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I've said elsewhere that "the FCC is going to-- well, really 'has proposed to', which means that they will--". The way I read it and understand the FCC to work, what they set forth in an NPRM is what they carry out in an R&O unless they're presented with sufficient reason to not do that; and there's no way they'll be persuaded to let existing 700-meg transmitters keep running.

In other interesting news, I found out who PISC are. Their board is made of CEOs of people like Google, AT&T, and so on, the New Owners of 700-megs. "Public Interest", my ass.

All that says to me that Google, AT&T, GTE, Microsoft, and whoever-the-hell-else owns 700 megs now have the FCC by the short hairs, and so we'll be lucky if we get anything out of the deal. Yippee-hurrah.