Re: Wireless microphone frequencies

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-mic… --- 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