FCC Spectrum Order

[Jon Fairhurst]

The FCC made some significant spectrum decisions today:

"...Notably, the Order eliminates the requirement that TV bands devices that incorporate geo-location and database access must also include sensing technology to detect the signals of TV stations and low-power auxiliary service stations (wireless microphones). It also requires wireless microphone users who seek to register in the TV bands databases to certify that they will use all available channels from 7 through 51 prior to requesting registration. Requests to register in the database will be public, thus allowing interested parties to weigh in on any given request."

"...today’s Order reserves two vacant UHF channels for wireless microphones and other low power auxiliary service devices in all areas of the country. It also maintains a reasonable separation distance between TV White Space device and wireless microphone usage permitted to be registered in the database"

Press release:
http://www.fcc.gov/Daily_Releases/Da...C-301650A1.pdf

Second Memorandum Opinion and Order
http://www.fcc.gov/Daily_Releases/Da...C-10-174A1.pdf

[Greg Bellotte]

"It also requires wireless microphone users who seek to register in the TV bands databases to certify that they will use all available channels from 7 through 51 prior to requesting registration."

What if our equipment doesn't cover ALL of those channels, but only SOME of them? Is the burden on us to acquire equipment that covers the entire ch7-ch51 spectrum BEFORE we can register? if not i encourage EVERYBODY on here with a wireless mic to register every unit they have.

I am VERY glad to see them reserve two channels in each market for low power use, that is tremendous!! since i work in many different markets it will be interesting to see which channels get left open, and if it coincides with gear I already own...

[Dean Sensui]

Just to clarify, this looks like the frequencies being discussed go from 175.25 MHz to 385.2625 MHz.

That's well outside the range currently being used by UHF wireless systems. And it seems most wireless mics sold today are in the UHF range.

[Robert Wiejak]

Originally Posted by Dean Sensui

Just to clarify, this looks like the frequencies being discussed go from 175.25 MHz to 385.2625 MHz.

That's well outside the range currently being used by UHF wireless systems. And it seems most wireless mics sold today are in the UHF range.

No, this is not the case.
You are looking at the wrong frequency table.
The frequency range you are describing (174 to 386 MHz) are the frequencies allocated to cable TV channels.
The “over_the_air” channel 7 frequency starts at 174MHz and the frequency of channel 51 ends at 698MHz.
So, this new memorandum actually affects all wireless microphones in 174MHz through to 698MHz.

I have not read all points, but here what caught my attention (and how I understand them, so it may not be 100% correct):

1. Spectrum of two channels (12MHz) will be allocated to low power devices in each geographical area (coordinated by local FCC office?).

2. Users of low power devices are encouraged to register their devices in order to coordinate frequency usage. The database is to be administered by third party, not yet decided who.

3. Big event organizers will be allowed, after registering with FCC, to use spectrum of more than 2 TV channels and will receive the same protection as licensed users.

4. Restrictions are placed on operating the wireless microphones in elevated terrain. For example, no wireless microphones above 76m (250 feet) of the local terrain. So, if you use 10’ per floor, no wireless microphones above 25th floor.

5. Radiated power restrictions: On unused channels from 21 to 51 except channel 37, up to 100mW EIRP and only 40mW EIRP on adjacent channel to TV station.

6. Along Canadian and Mexican boarders, Canadian and Mexican TV stations will automatically be entered into the database and their frequencies protected.

7. “… The Commission requires… …have a capability to sense TV broadcast and low power…”: in other words, before you turn the transmitter ON, listen to your receiver and if there is a hint of a signal, change the frequency.

8. Before operating your wireless microphone obtain the current local list of permitted channels (FCC?).

[Chuck Fadely]

We just spent $10k to replace block C mics and now, who knows if our new ones will work?

Ars Technica has a take on it here. New FCC white space rules: inside the Satanic details

FCC favors 'licensed' radios - and no one licenses their wireless mics, so to the FCC the millions?? - at least tens of thousands - of wireless mics don't exist. We and the churches and the theaters of the US are going to have to spend big bucks again, I think.

And just to get the words in here for the search engines, this is about white spaces, the frequencies between TV channels where our mics work.

[Dean Sensui]

Originally Posted by Robert Wiejak

...no wireless microphones above 76m (250 feet) of the local terrain. So, if you use 10’ per floor, no wireless microphones above 25th floor.

The FAA considers structures to be part of the terrain (lucky for airline passengers and people who live in high rises). :-)

[Robert Wiejak]

Since I can’t edit my original post let me just update my points this way:

2. I misinterpreted that one. There is no requirement to register all wireless microphones, only the ones that require protection.

Originally Posted by Dean Sensui

The FAA considers structures to be part of the terrain (lucky for airline passengers and people who live in high rises). :-)

In this case FAA has very little to do with FCC.
But, the wording is such that I missed one little word ‘fixed’. That may effectively exclude all wireless microphones because as defined ‘fixed TV band devices’ are allowed to transmit up to 4W EIRP unlike microphones that are allowed only 100mW max.
But on the other hand I can see them restricting it: It all has to do with ‘radio horizon’. At the ground level, taking into consideration average buildings construction, the working horizon (distance) maybe about 100m, well within the proposed ‘protection distance’. Higher you go, generally there is less structures translating into less attenuation and due to height your effective radio horizon extends well beyond the proposed ‘protection’ distance. Few years ago I was involved in experiment where using a 2.4GHz 75mW video transmitter and the right type of antennas on both ends, we successfully transmitted the signal 175Km (about 110 miles) from a mountain top to a city center. So if there is just air in between Tx and Rx antennas (LOS), you can go great distances on very little power and this maybe why FCC is restricting the height.

[Greg Bellotte]

I have a problem with the proposed protection distances. I don't think 1km is going to give me much if any protection. I regularly get 300m using a 30mW transmitter with 4' ant. height and receive antennas at 15' height. Using 100-250mW transmitters I can cover a whole golf course, usually more than 1kM end-to-end. 4W at only 100' height can go for a few MILES...250' high will carry ever further. I'm thinking 1kM away from a 4W transmitter will not only interfere, but give me excellent reception of said transmitter...

I'd feel a lot better if the protection distance was 4-5 kM.