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USA Wireless Microphone Future - Bad News and Good News and Bad News

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Richard Crowley
USA Wireless Microphone Future - Bad News and Good News and Bad News
on Nov 7, 2015 at 1:11:53 pm

I just came across this 84 page document posted by the FCC:
http://transition.fcc.gov/Daily_Releases/Daily_Business/2015/db0811/FCC-15-...
Title: "In the Matter of: Promoting Spectrum Access for Wireless Microphone Operations [vs.] Expanding Economic and Innovation Opportunities of Spectrum through Incentive Auctions." The [vs.] was supplied by me as a snarky editorial remark.

For those who only recently came out from under their rock: The FCC has already taken away the popular 700 MHz band where many (most?) of our wireless audio gear was operating, and it looks like the 600 MHz band has only a short time left (a year or two?)

The rapid increase in demand for consumer digital wireless devices (cell phones, tablets, etc.) of course is driving the need for additional spectrum to accommodate all the high-speed (read: wide-band) users so we can stream the latest mindless sit-com (or "reality show") in full 4K HD to a 4 inch screen while we dangerously attempt to drive down the highway. I guess that is the price we pay for living in a modern, high-tech society.

The good news is that at least the wireless gear manufacturers have got the FCC to acknowledge that wireless microphones are a legitimate and necessary user of RF spectrum and should be officially accommodated even if they only continue to consume "table-scrap leftovers" of spectrum.

And the bad news is that wireless microphones (as most all other users) continue to be pushed up into higher and higher frequencies. One benefit of higher frequencies is that it better accommodates digital operation which certainly has quality and operational benefits. But higher and higher frequencies also make propagation more difficult because of more severe line-of-sight limitations caused by "RF shading" from having the transmitter on the other side of the subject's body and/or increased absorption and/or reflection phenomenon from higher frequencies.

I have concerns about the use of the 2.4GHz ISM band as we have seen in several new products from Audio Technica, Rode, and even Azden because that band is shared with WiFi, Bluetooth, and even microwave ovens and 2.4GHz already seems "over-booked" even before wireless microphones "discovered" it.

Alas, the document is written in a deadly combination of leagaleze and "government-speak", and it will take some time to read through the whole thing and try to digest what they are saying (if there is actually any clear indication in there at all). It looks like the commissioners' statements at the very end of the document may be a more "human-scale" place to start reading.

In any case, we can probably kiss our 600MHz gear good-bye in the near future and start shoving more $$$ into the piggy-bank in preparation for buying new wireless gear.


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Ty Ford
Re: USA Wireless Microphone Future - Bad News and Good News and Bad News
on Nov 7, 2015 at 3:16:05 pm

Hi Richard,

In August of this yes, 2015, the FCC did a repositioning for the 600-700MHz band and said some wireless use would be permitted. When I found it, I posted it in as many places as I thought useful. Exactly how much was lost to me in their explanation. Bottom line: there may still be some hope for the 600 MHz band.

As regards audio of the wi-fi band. As I think you know, I have a couple of the Audio-Technica System 10 rigs. Outside in a totally filled parking lot I got 150 feet. That's proves that System 10 does pretty well in very reflective metallic environment.

I'm not sure all the systems are triple back-up the way System 10 is. First, the receivers are at least antenna diversity, so if one receiver doesn't get the signal, hopefully the other will. Second there is data redundancy, the same bit of audio is represented twice in the transmitted signal (sort of like the block redundancy in DAT machines -- remember them?) Third, the transmitters and receivers are always "talking to each other." When a frequency is chosen, there is always a backup frequency chosen. If communication breaks down on the first frequency, the system shifts to the second frequency. After it does, the system then seeks out a new backup frequency. So that's Belt, Suspenders and what…raincoat. Again, I do not know if the other systems have this sort of protection.

There is still a problem, today 11/7/2015) with very small lavs that were designed before 2.4 GHz was rolled out. The RodeLink lav can pickup 2.4 GHz noise if the mic that comes with it is too close to the transmitter. The System 10 gear is good with the AT MT830 lav and BP892 ear-worn lav, but the micropoint BP896 still picks up the interference. AT is aware of the problem and is working on it.

I used the System on a shoot in downtown Baltimore. I had a problem with my G2. The talent likes wearing lots of metal bracelets. It seemed like they may have been contributing to some reflection interference. Here's a clip of that piece. The MT830 lav is placed at the bottom of her V neck top.







Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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