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1h. Re: Wireless Mic Recommendations?
    Posted by: "Glenn Manuel"
    Date: Tue Jan 5, 2016 12:13 pm ((PST))

I was trying to keep it simple, but there are questions, so here are the
gory details.

Yes, I love our EW100 also, but it is no longer legal to use it. As part
of the digital TV conversion, the FCC re-assigned the 700 Mhz band to
public services. Wireless mics are no longer allowed to use those
frequencies. Look on the back of your EW100 transmitter and/or receiver.
If it says the frequency range is between 698 and 800 Mhz, it has been
illegal to use it since June 2010.

From
https://www.fcc.gov/consumers/guides/distribution-sale-and-use-wireless-microphones-operating-700-mhz-band-prohibited

--- quote As of January 15, 2010, the FCC prohibits the import, sale,
offer for sale or shipment of wireless microphones and other low power
auxiliary stations (i.e. similar devices) intended for use in the 700
MHz Band in the United States. This prohibition will help complete an
important component of the DTV transition by clearing the 700 MHz band
to enable the rollout of new communications services for public safety
and for next generation wireless services for consumers. ... *As of June
12, 2010, use of wireless microphones (and similar devices certified as
“low power auxiliary stations”) operating in frequencies between 698 and
806 MHz (the 700 MHz Band) is prohibited.* ... Using the 700 MHz Band
for a wireless microphone (or a similar device) after June 12, 2010
could be extremely dangerous and could even be life threatening. Police
and fire departments, and other public safety groups, use frequencies in
the 700 MHz Band. Interference from wireless microphones can affect the
ability of public safety groups to receive information over the air and
respond to emergencies. Harmful interference to these communications
could put you or public safety personnel in grave danger. In addition,
use of your microphone can cause  unlawful interference to consumer
services provided using the 700 MHz Band. --- unquote

FYI, 698-806 Mhz covers old TV channels 52-69, which are no longer
used for TV.

Most wireless mics now use the UHF TV frequencies, which spans 470 Mhz
(channel 14) to 698 Mhz (channel 51). But at least some of that is not
necessarily safe. From
https://www.fcc.gov/general/wireless-microphones-0

--- quote In the May 2014 Incentive Auction Report and Order, the FCC
adopted rules to implement the broadcast television spectrum incentive
auction, which will involve reorganizing the existing television band
and repurposing a portion of the UHF television band for new wireless
broadband services, which will no longer be available to wireless
microphones.  This repurposing of the 600 MHz spectrum will, therefore,
affect wireless microphone operations across the current TV bands in the
future.  Until the incentive auction involving this TV band spectrum is
completed and the FCC issues a channel reassignment Public Notice
establishing the final 600 MHz Band plan, the impact of repurposing on
wireless microphones will not be known because the specific UHF
frequencies that are being repurposed for wireless services and no
longer available for wireless microphones will not be known. --- unquote

To prevent future obsolescence, it seems wise to avoid the "600 Mhz
spectrum". I could not find an exact definition of this, so it is
not clear which TV channels this includes. It seems like the FCC
won't decide on the exact frequencies until later when it decides to
take action.

For each of their wireless mic series, most manufacturers offer several
different frequency bands. Each mic band typically covers about 3 or 4
UHF TV channels. Examples: Sennheiser XSW 52 (good replacement for
EW100, about $450) offers 2 bands: XSW 52    548-572 MHz = TV Channels
27-30 (sometimes indicated as band A) XSW 52-B 614-638 MHz = TV Channels
38-41 Shure BLX (about $300) offers 3 bands: H9  (512.125 – 541.800 MHz)
= ch 21-25 H10 (542.125 – 571.800 MHz) = ch 26-30 J10 (584.150 – 607.875
MHz) = ch 33-36

You have to pick a mic band that works best for the TV stations in your
location. If you are a traveling caller with your own mic, what works
great in one city might have interference problems in another city.

The Sennheiser web site has a nice frequency finder.
http://en-us.sennheiser.com/service-support-frequency-finder Enter a
city or zip and it lists all the TV stations and their frequencies, to
help you decide which mic band to get. The "Range" parameter is a list
of their own wireless mic products. If you choose one, it highlights the
MHZ column to show the bands available for that product. The "ERP"
column is the transmitter power, and the "Prx" column is the estimated
signal strength at the specified location (takes into account ERP and
distance from transmitter). If there is no vacant channel, you should
try to use a channel with the lowest Prx.

There are other interesting quirks. There is another class of device
called "White Space Devices" (WSD) which are allowed to share the TV
spectrum. White Space means using the vacant or blank or white or unused
space between active TV channels. Wireless mics compete with WSDs in
addition to the TV signals. Channel 37 is prohibited for wireless mics
and WSDs. In each location, the FCC tries to reserve the 2  unused TV
channels closest to 37 (one above one below) for wireless mics. The WSDs
are not allowed to use those channels, so those are the preferred
frequencies for wireless mics. This web site lists the Reserved
channels: http://whitespaces.spectrumbridge.com/whitespaces/Home.aspx
Select "Wireless Microphone", enter your zip, and click Search. Channels
listed as Reserved should be the best for wireless mics. Ideally, try to
find a mic freq band that includes one or both. Again, that will vary
with location.

Besides the UHF TV band, the FCC allows wireless mics to operate
unlicensed in other frequency bands: 88-108 Mhz (FM Radio) 54-72, 76-88,
174-216 Mhz (TV VHF) 902-928 MHz, 2.4 GHz, 5 GHz (ISM bands) 1920-1930
MHz (unlicensed PCS) Ultra-wideband (3.1-10.6 GHz)

Even more gory details are in the FCC publication 14-45:
https://apps.fcc.gov/edocs_public/attachmatch/FCC-14-145A1.pdf

Summary: The use of the TV spectrum is OK for a specific location if
you can buy a mic with a freq range compatible with your TV stations,
except the FCC is thinking about eliminating use in the "600 Mhz"
band, whatever that might turn out to be, and of course, new stations
might pop up.

I assume the 2.4 Ghz and 5 Ghz bands are the same as used by WIFI, which
is becoming ever more crowded, so are best avoided.

That seems to leave the 902-928 Mhz band as the best choice. It is used
by the Shure PGX series. I don't know if any other vendors use that
band also.

-- Glenn