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CALLERLAB
On 1/6/2016 12:34 PM, David Kirchner dekirchner@gmail.com
[trad-dance-callers] wrote:
> Hi all,
>
> There is a conversation currently taking place on the contra sound
> listserv about wireless microphones. I know that I am not the only
> caller that lurks in that group, but many of you may not follow it. I
> thought this long post from Glenn Manuel (Dallas TX) was very
> informative and worth crossposting here, though note the info is
> US-only. For more info about that listserv, see:
> http://liveedge.net/2014/67/contrasf-contra-sound-forum
>
> David
> St. Paul, MN
>
> ----------------------------------------------------------
> 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
>
>
>