Montana's Ham Radio Forum

Although not ham radio related, this rule change does impact various schools and churches that use wireless microphones. As hams, many of us end up being the resident advisor at school and church functions for all things electronic. If an organization you are involved with is using 700 MHz wireless mics, now would be a good time to give them a heads-up.

Here is the link from the FCC web site: http://www.fcc.gov/cgb/wirelessmicrophones/

Here is the text of the FCC announcement:

OPERATION OF WIRELESS MICROPHONES IN THE 700 MHZ BAND IS PROHIBITED AFTER JUNE 12, 2010

Under a new FCC rule, anyone who uses a wireless microphone that operates in the 700 MHz Band will have to stop operating their wireless microphone no later than June 12, 2010. To see if this law affects your wireless microphone, check our Manufacturers Equipment list.

Why did the FCC make this rule?

Certain wireless microphones have operated in frequencies that are needed for public safety. When these microphones were first designed, the frequencies they used were in between the frequencies that television stations used to broadcast television programs. With the completion of the digital television (DTV) transition on June 12, 2009, television stations no longer use the frequencies between 698 and 806 MHz (the 700 MHz Band) for broadcast. These frequencies are now being used by public safety entities (such as police, fire and emergency services) and by commercial providers of wireless services (such as wireless broadband services).

The wireless microphones that had been operating in the old TV broadcast channels can cause harmful interference to these public safety and wireless consumer services. Therefore, all users of wireless microphones (or certain low power auxiliary stations) that operate on any of the frequencies in the 700 MHz band – including both licensed users (under Part 74) and unlicensed users – now have to stop operating in this band.

The FCC is only prohibiting the use of wireless microphones that operate in the 700 MHz Band. You may continue to use wireless microphones that operate on other broadcast frequencies. Microphones with cords are not affected by the FCC’s decision.

Thanks for the good Heads Up Bruce

Are 700 MHZ microphones common??? I can cee NO enforcement of this new rule! What are they gonna do, come into church and shut 'em down?

I checked the wireless mic in use at my church today and found it to be on 193 MHz. I have also seen other wireless mics that operate in the 174 MHz range. I have not seen any 700 MHz wireless mics - perhaps they were used by the television industry for their mobile news teams reporting "live" at the scene. As such, they would have been for short range work between the reporter and the news truck parked nearby.

Since the band is being reallocated to public service functions (fire, police, ambulance) I expect any reported interference problems will get FCC attention. The higher power of the public service mobile and base station radios will render any wireless mic system unuseable anyway. But those who insist on still using them will probably be reported to the FCC by the public service function that is picking up their signal. I expect the signal would be so weak that it would be a minor nuisance to the high-power 2-way radio user. Still, interfering with fire/police/ambulance communications is a quick way of drawing the attention of the FCC. So, yes - the church would be contacted and told to turn-off their system ASAP due to causing interference to a public safety function.

Well, I don't know where they came from, but when I checked the wireless microphone system in use at our church recently I found two additional ones. One operates on 169 MHz and the other one on 736 MHz. The second one falls right into the middle of the now reallocated 700 MHz band (698-806 MHz).

The wiring from the hard-wired microphones, as well as all the wiring going out to all the speakers is unshielded twin-lead. It appears to be one step up from field-phone wire. Now I know why last year we had a problem picking up signals from a radio station. The audio was coming out of the speakers at a low level, but was still audible. The problem eventually went away, but with hundreds of feet in unshielded wiring going out to the speakers, it is like a cage dipole seeking out weak signals to suck in and pass on to the speakers!

Because some folks know I am an Amateur Radio operator, they turned to me and asked "What can we do about these stray signals getting into our public address system?" They were also quick to place the blame, "It must be coming from that huge ham radio tower a few blocks away!!!" I was equally as quick to dismiss their initial culprit. Since we could hear the low level audio containing music and announcements, I pointed out that it was obviously programming from a radio station - NOT a ham radio operator. As I mentioned before, the problem eventually went away. Since that incident the ham radio tower has been dismantled and removed, so it cannot be blamed the next time the interference happens.