Topic: AT853a picks up radio stations

[bcarrigg90]

Hello all, I'm new to this forum so excuse me if this isn't the best section to ask this question.

I'm setting up to run sound for our Christmas program here at Cincinnati Christian University. I have a pair of AT853a's that I'm using for choir overheads. The issue I'm having is that one of them seems to be picking up radio stations. Does anyone have any experience with these mics? My first instinct is a bad ground connection, but I I've swapped cables and haven't been able to find any issues there. Could it be a problem with the power pack? It happens on both battery and phantom power.

[ArchivalAudio]

FM interference can be caused by  a bad cable, or any audio or mic cable crossing a power cable .
Usually if you are using shielded cables - such as  the ones on the AT 853's it should be fine. 
ANYTIME a mic cable crosses over a power cable it should cross at 90° this should cut out the fm interferences.


You might include more information... are you hanging them above the stage? near lighting equipment? that could cause issues because of the relatively high current the  lights are drawing.



good luck
--Ian

[TimSmith]

I have the same problem in my home when I use a preamp (I have CA-9200) in the chain. I tried everything I could, but the only thing that helps is getting to some other place. No problems at the basement or local venues or my grandma's house. It seems that some kind of an FM transmitter is nearby.

I don't know if that could be the cause in your case though... Just a suggestion. Try testing mics in different places.

[Church-Audio]

I have the same problem in my home when I use a preamp (I have CA-9200) in the chain. I tried everything I could, but the only thing that helps is getting to some other place. No problems at the basement or local venues or my grandma's house. It seems that some kind of an FM transmitter is nearby.

I don't know if that could be the cause in your case though... Just a suggestion. Try testing mics in different places.

Its not the preamp its the gain that you are using that is boosting the signal being picked up by the mics possibly. I would think you have some  ground issue with these mics or if it has my mod it was done wrong
Chris

[TimSmith]

I have the same problem in my home when I use a preamp (I have CA-9200) in the chain. I tried everything I could, but the only thing that helps is getting to some other place. No problems at the basement or local venues or my grandma's house. It seems that some kind of an FM transmitter is nearby.

I don't know if that could be the cause in your case though... Just a suggestion. Try testing mics in different places.

Its not the preamp its the gain that you are using that is boosting the signal being picked up by the mics possibly. I would think you have some  ground issue with these mics or if it has my mod it was done wrong
Chris

Well, I'm not picking any radio without the preamp with the same amount of gain from my recorder (the mics are CA14 - I have two pairs). I think it's just a crazy environment. My synthesizer catches some FM too and it didn't, say, 7 years ago.

[DSatz]

Is this problem still occurring?

I'd like to help but am completely unfamiliar with these microphones. Assuming that the outer housing of the microphone is made of metal, is there a metal screw (or more than one) that holds the housing on to the innards of the microphone? If so, have you tried tightening those screws, and making sure that they are contacting a clean metal surface on the innards of the microphone? You want to make sure of unbroken continuity between the microphone housing and (via the output connector) the cable shield. Even small gaps can make a difference at radio frequencies.

But if this is a "remote capsule" type of microphone as Jon Stoppable's reply suggests, then you're in risky territory to begin with. Such systems generally use unbalanced cabling and connections which are inherently much more vulnerable to RF than balanced cables and connections. Not sure what to tell you in that case; there are some environments in which such microphones just can't be used reliably, and increasingly so with the proliferation of cell phones and mobile devices. On the other hand, the radio signals may be entering output of the microphone amplifier, which is balanced, no?

I would also suggest giving A-T a call. While their stuff is manufactured overseas, they have a major home office in Ohio with technical experts on hand, and they seem to be a customer-service-oriented company from my dealings with them.

--best regards

[stevetoney]

Gilligan got hit in the head and his fillings picked up radio stations.  You might want to check re-runs of Gilligans Island to see what the Professor recommended.