Help some mics cutting out show opens Thursday

JimP0771

Well-Known Member
Hi all

It has been a long time since I have posted anything on here. I have in the past few days been doing sound for local High School's musical and this past Saturday's rehearsal went great with the sound however last night Monday I an issues with 2 Microphones. The 2 Lead's keep cutting out. Sort of like RF cut out. They are Audio Technica 2000 series with a earpiece microphone. I am wondering if there is something that is now running in the school that is transmitting a radio frequency that was not running on Saturday where there were no school in session that may be interacting with the wireless mic frequencies. Could it be the battries?


Any ideas

Thanks
 

jkowtko

Well-Known Member
For frequency issues, you could try turning off the transmitters and see if the receivers pick up anything. I've run into this problem in the past, had to reset a couple of channels once or twice due to sos very loud noise being broadcast ...
 

halenono

Member
If you haven't already, try trading out components to see if the problem follows the component. Give your leads different mics (same transmitters) and give those mics to other actors. If the problem stays with the leads and doesn't follow to the other actors, it isn't the mics. Try different transmitters but on the same frequencies. If problem persists, try different frequencies.
 

TheaterEd

Renaissance Man
Fight Leukemia
Just some other ideas. Did your kids have cellphones in their pockets on Saturday? Was there something going on in the building on Saturday that doesn't happen during the week? I'm thinking like a robotics club or something that might use similar frequencies for different kinds of equipment, or a marching band that has microphones for the conductors.
 

FMEng

Well-Known Member
Fight Leukemia
A good description of the dropout will help us determine if it's an audio dropout, caused by something like a failing mic cable, or an RF dropout from interference or low signal. When it happens, is it just silence, or is there a loud pop or bang. Do you hear any noise when it starts or ends?
 

TimMc

Well-Known Member
Premium Member
Any chance these systems have operating frequencies >608.000 mHz? Have any local TV stations finally "moved" RF channels in compliance with the broadcast RV re-pack of 3 years ago? (more bkg below)

Are the transmitter pack antennae touching the performer's skin, or might they be folded/caught between the transmitter case and body-side of the transmitter pouch/belt? Are the transmitters under costumes with metallic thread (or aluminized Mylar®)?

This story goes back to the original digital TV re-pack about 15 years ago that allowed the FCC to comply with a Congressional mandate to make the 700 mHz band more financially productive, history thereof: the FCC auctioned 10 year licenses to "the usual suspects" in mobile communications - ATT, T Mobile, American Tower, Verizon, and some smaller players. Some TV broadcasters changed RF frequencies, some only changed modulation and input for digital video and the more effective use of each TV channel's RF territory. Lather, rinse, repeat for the 600 mHz band, the TV re-pack began 4 years ago (and hence my question about operating frequency) and was slowed considerably by Covid-blamed supply side issues with various parts of broadcast hardware.

It was in the 700 mHz re-pack that a local youth musical theater company got tripped up. Local TV 10 had to change RF frequency (they kept the virtual dial channel number) down into the 600 mHz band, where the company had several channels of fixed-frequency wireless systems. Packs 1 & 2 were the female and male leads, respectively. Every time the male would be stage right, facing stage left, his signal would fade away, sometimes rather abruptly. When he turned to face stage right or downstage, his mic would quickly feed back. As the mixerperson, this was Not a Good Thing for my reputation... and I was getting what sounded like a bad mic cable on one or more of the PCC-160 floor mics. The long troubleshooting process led to these conclusions: 1) The center of TV 10's new RF home was the frequency of Pack 2; receivers (all 1/4 wave antennae, receivers stacked up, a seriously compromised situation on its own) were stage left, by the SM, and when the actor's body was between the Pack and them, the TV 10 transmitter was strong enough to desensitize the front end of the receiver but when the pack RF was strong enough, it all worked after the receiver wasn't saturated. 2) the intermittent "bad ground on a phantom powered mic" like the PCC-160s... was an IM hit of RF when Pack 1, Pack 6, and Pack 9 were on stage together, and only in certain physical places w/r/t each other. 3) I developed a strong dislike for the vacuous use of RF for video content delivery (we lost precious, unlicensed spectrum so folks can watch Real Housewives of Steaming Video and live stream their karaoke performances to Face Space, bah AND humbug, but I digress).

/little story

So... if your wireless mics operate above 608 mHz, you're likely getting RF hits from T-Mobile / ATT/ American Tower transmitters on their LICENSED frequencies. If you're down in the 500 mHz band, it's possible that a re-packing TV station got their back-ordered antenna/transmitter put on line since your previous show and you need to do a new coordination. While it's possible for land mobile (police, taxi, business) services to interfere, in all but the large metro areas they aren't a significant factor. OTOH one of the venues I routinely work is 2 miles from an airport with significant RF testing and development for aviation (weather radar, a variety of open and encrypted communications, navigation and remote operation) and as far out-of-band as they may be relative to 500mHz... they DO have an impact and it can vary with whatever devices are under test at Honeywell or Textron or Bombardier. Tiny story (Honest!) - about 8 years ago, Beatles tribute act is playing their first show with IEMs (the Beatles did not have wedge monitors). "George" says "well, it will be lovely once you turn off the flanger in my head." Wireless Work Bench wasn't much help; I think they randomly retuned his receiver until the noise went away and then coordinated the other 3 with that frequency. /tiny story
 

FMEng

Well-Known Member
Fight Leukemia
The second TV repack was completed some time ago, but with covid shutdowns, this could be the first use of the wireless mics since a megawatt of transmitter moved on or adjacent to the mic frequencies. An AT 2000 receiver may not be terribly selective either.
 

BCAP

Well-Known Member
This is pretty obvious, and I apologize - I'd first rule out your microphone hardware and actor installation on those two units by doing an extensive and thorough cable wiggle test offline. In order to test for a failure in the mic cable or the connector to the transmitter pack. I assume you maintain consistent microphone & transmitter hardware-to-actor assignments throughout the show run, which is always a good idea, especially because when issues develop with a specific microphone or transmitter it becomes increasingly difficult to trace these problems down if ANY of the equipment (even a lapel, hair or headset microphone) floats between actors as I have seen with some shows. Basically, my personal assumption with wireless equipment is that it's going to fail during the show at the last opportune time and I take all steps possible to try to mitigate that.

Has your wireless setup been effectively frequency coordinated? (recently) If not, you might want to consider turning all mic transmitters off and doing an RF scan to determine what's in the environment. With a device like RF Explorer and computer software, or some other analyzer. Coordination software like Wireless Workbench can import RF scans from these devices and can calculate new frequencies that avoid problems.

Aside from that a few other thoughts - don't have transmitter pack antennas coming into contact with sweaty skin, ensuring that transmitter pack installations on actors don't bend the antenna or put it in a weird position. Be careful with taping - skin taping, with "mic tape" like Nexcare, etc. Done improperly it can cause cable strain and cutouts. Rare, but I've seen it.

Hope this helps.
 

JimP0771

Well-Known Member
Hi all I figured it out and fixed the problem. It was a frequency issue. What would happen is that the actors would walk to one area of the stage and the Wireless body mic would cut out and when they walked to the other side they would be heard fine. I just change the frequency of them till I found ones that were not showing any RF activity while the body packs were turned off. That fixed the issue. Other than that. I had a few of the small headset lav cables that plug into the body pack that goes to the mic break but I had extras and just swapped them out. The show sounded good and was a smash hit and closed yesterday.
 

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