Wireless Mic Issues

nickbits · 28th June 2010, 11:03 PM

Hi All,

I am having a minor issue with a wireless mic set-up. I believe the wireless mic is a Shure SM-318 using the 114/116MHz frequencies (I think). Anyway, I have tested it on 5 or more systems and it works perfect. I am attempting to use it with a society I am involved with.

I turn up early to the meetings, connect the wireless receiver into the wall (there is already an amp and speakers in the room we use). Test it and it works fine. When the meeting starts properly there are 50 or more people present. The microphone then just doesn't seem to work correctly, sound either fails all together or comes and goes, or seems crackly.

Again after the meeting has finished and most have left, I test it again and again it works fine. Initially we thought it was the equipment but after testing it before and after meetings and on other systems, I am struggling to find the cause and/or a solution. After tonight I am assuming it is not the equipment as such.

I am assuming something is causing interference. Could it be hearing aids? I only ask as we only get a problem when we have an audience present. Hence I am assuming it is linked to something in the audience.

Any thoughts or suggestions are welcomed.
Nick

nickbits · 28th June 2010, 11:38 PM

Hi All,

Think I may have just answered the question. When writting the post above it occurred to me that the mic is VHF. Doing a quick google for hearing aids it shows some also using VHF. I don't know the exact frequencies but am assuming that this is the problem of the mic and hearing aid interfering.

I therefore assume that a UHF system wouldn't have the same problem. Can anyone confirm this? If so, can anyone suggest an inexpensive wireless (tie clip) system?

Cheers,
Nick

imix500 · 29th June 2010, 12:17 AM

Hi,
It's possible hearing aid devices are causing interference, but lots of things can cause problems in the VHF band. Are there any RF based hearing impaired transmitters in the room?
UHF is much less likely to be affected if it is from VHF hearing impaired systems, but UHF is becoming tricky with all the bandwidth reallocation that's been going on the past few years.
There are many cheap UHF systems, but you get what you pay for with wireless. At minimum, I would suggest a system with a true diversity receiver and research what DTV stations are operating in your city.

Enzo · 29th June 2010, 02:00 AM

Work with a pro dealer. You should be able to try a system on approval. They don;t want to sell you something you won't be happy with. It does sound like interference. getting a system in a different RF band would seem expedient.

nickbits · 29th June 2010, 06:41 AM

Hi,

Thanks for the replies. I know there are various things that could cause interference but thought it may be hearing aid related as the problem only occurs when people start to turn up. So thought it could be something related.

I am unaware of a hearing loop or similar around the room, but am now investigating that possibility.

As for DTV and reallocation, I had thought about that with UHF. Anyway, will investigat the above first, as getting what you pay for, I do agree but being a small non-profit group, we simply cannot afford much, hence having gone for a VHF system.

Anyway, thanks for the ideas guy, very much appreciated.
Nick

Speedskater · 29th June 2010, 06:10 PM

The US FCC department recently (when all TV stations went digital) changed the frequency bands that wireless mics are permitted to use. So other new devices may be now operating in a mic's older frequency band.

nickbits · 29th June 2010, 08:18 PM

Hi,

I am in the UK and although the same hasn't happened here yet, I dare say it will.

Even if that was the case, it wouldn't explain this situation. That is everything works fine until our audience turn up. The chances of our audience having any technology, other than a hearing aid or mobile phone, that could cause interference is slim.

That is what makes me think the problem is related to the hearing aids, or perhaps an induction loop system for the hearing aids.

Anyway, thanks for the info, something to watch out for in the future.
Nick

Speedskater · 1st July 2010, 05:32 PM

If you are interested in other strange problems, the EMC (EMI/RFI) group in the UK publish a journal with a regular column "Banana Skins" that documents other unusual problems.
You may have to do a simple sign-up.

EMC Information Centre - The EMC Journal (Free in the UK)

firechief · 1st July 2010, 07:49 PM

Hearing aids are not likely to be the cause. No radiated RF to speak of, and because they are made to go in the ear, they are subject to very tight regulation. What speedskater said about the change in the spectrum alocation could be a clue. Try a longer wire between the receiver and the amp so that you can move the receiver around when the problem occours. You might find a sweet spot that cures the problem.

nickbits · 1st July 2010, 08:44 PM

Quote:

Originally Posted by Speedskater

If you are interested in other strange problems, the EMC (EMI/RFI) group in the UK publish a journal with a regular column "Banana Skins" that documents other unusual problems.
You may have to do a simple sign-up.

EMC Information Centre - The EMC Journal (Free in the UK)

Will give that a try, thanks for the tip.

Nick

28th June 2010, 11:03 PM	#1
nickbits diyAudio Member Join Date: Jun 2010 Location: UK	Wireless Mic Issues Hi All, I am having a minor issue with a wireless mic set-up. I believe the wireless mic is a Shure SM-318 using the 114/116MHz frequencies (I think). Anyway, I have tested it on 5 or more systems and it works perfect. I am attempting to use it with a society I am involved with. I turn up early to the meetings, connect the wireless receiver into the wall (there is already an amp and speakers in the room we use). Test it and it works fine. When the meeting starts properly there are 50 or more people present. The microphone then just doesn't seem to work correctly, sound either fails all together or comes and goes, or seems crackly. Again after the meeting has finished and most have left, I test it again and again it works fine. Initially we thought it was the equipment but after testing it before and after meetings and on other systems, I am struggling to find the cause and/or a solution. After tonight I am assuming it is not the equipment as such. I am assuming something is causing interference. Could it be hearing aids? I only ask as we only get a problem when we have an audience present. Hence I am assuming it is linked to something in the audience. Any thoughts or suggestions are welcomed. Nick

29th June 2010, 06:10 PM	#6
Speedskater diyAudio Member Join Date: Sep 2002 Location: Lakewood, Ohio	The US FCC department recently (when all TV stations went digital) changed the frequency bands that wireless mics are permitted to use. So other new devices may be now operating in a mic's older frequency band. __________________ Kevin

1st July 2010, 05:32 PM	#8
Speedskater diyAudio Member Join Date: Sep 2002 Location: Lakewood, Ohio	If you are interested in other strange problems, the EMC (EMI/RFI) group in the UK publish a journal with a regular column "Banana Skins" that documents other unusual problems. You may have to do a simple sign-up. EMC Information Centre - The EMC Journal (Free in the UK) __________________ Kevin

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
wireless mic transmitter convert for guitar?	pkrieter	Instruments and Amps	11	22nd January 2009 09:27 PM
Need simple low pass for wireless Mic	mlanier911	Instruments and Amps	10	19th January 2007 11:53 AM
'Tube' preamp bad for measurement mic? also Apex mic question	morbo	Multi-Way	10	23rd March 2005 10:19 AM
Behringer measurement mic issues	npdang	Multi-Way	4	21st January 2005 04:09 AM
What mic preamp for Behringer testing mic	The Paulinator	Multi-Way	1	6th April 2003 07:02 PM


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

28th June 2010, 11:38 PM	#2
nickbits diyAudio Member Join Date: Jun 2010 Location: UK	Hi All, Think I may have just answered the question. When writting the post above it occurred to me that the mic is VHF. Doing a quick google for hearing aids it shows some also using VHF. I don't know the exact frequencies but am assuming that this is the problem of the mic and hearing aid interfering. I therefore assume that a UHF system wouldn't have the same problem. Can anyone confirm this? If so, can anyone suggest an inexpensive wireless (tie clip) system? Cheers, Nick

29th June 2010, 12:17 AM	#3
imix500 Proud Union Member diyAudio Member Join Date: Mar 2004 Location: Nashville, TN	Hi, It's possible hearing aid devices are causing interference, but lots of things can cause problems in the VHF band. Are there any RF based hearing impaired transmitters in the room? UHF is much less likely to be affected if it is from VHF hearing impaired systems, but UHF is becoming tricky with all the bandwidth reallocation that's been going on the past few years. There are many cheap UHF systems, but you get what you pay for with wireless. At minimum, I would suggest a system with a true diversity receiver and research what DTV stations are operating in your city.

29th June 2010, 02:00 AM	#4
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	Work with a pro dealer. You should be able to try a system on approval. They don;t want to sell you something you won't be happy with. It does sound like interference. getting a system in a different RF band would seem expedient.

29th June 2010, 06:41 AM	#5
nickbits diyAudio Member Join Date: Jun 2010 Location: UK	Hi, Thanks for the replies. I know there are various things that could cause interference but thought it may be hearing aid related as the problem only occurs when people start to turn up. So thought it could be something related. I am unaware of a hearing loop or similar around the room, but am now investigating that possibility. As for DTV and reallocation, I had thought about that with UHF. Anyway, will investigat the above first, as getting what you pay for, I do agree but being a small non-profit group, we simply cannot afford much, hence having gone for a VHF system. Anyway, thanks for the ideas guy, very much appreciated. Nick

29th June 2010, 08:18 PM	#7
nickbits diyAudio Member Join Date: Jun 2010 Location: UK	Hi, I am in the UK and although the same hasn't happened here yet, I dare say it will. Even if that was the case, it wouldn't explain this situation. That is everything works fine until our audience turn up. The chances of our audience having any technology, other than a hearing aid or mobile phone, that could cause interference is slim. That is what makes me think the problem is related to the hearing aids, or perhaps an induction loop system for the hearing aids. Anyway, thanks for the info, something to watch out for in the future. Nick

1st July 2010, 07:49 PM	#9
firechief diyAudio Member Join Date: Sep 2008 Location: Near Seattle Wa	Hearing aids are not likely to be the cause. No radiated RF to speak of, and because they are made to go in the ear, they are subject to very tight regulation. What speedskater said about the change in the spectrum alocation could be a clue. Try a longer wire between the receiver and the amp so that you can move the receiver around when the problem occours. You might find a sweet spot that cures the problem.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read