Radio mic audio artefact

imaginACTION_films wrote on 8/1/2014, 10:57 PM

Hey Guys,

Doing some single person performances with my Canon XA10. Using a Sony URX-P2 receiver and UTX-B2 transmitter for the radio mic. The receiver is normally mounted on the cold shoe. We’ve used this system with almost no problems in the field in several hundred different locations around the country.

Yesterday, I noticed during recording that there was a small but audible hiss pulsing each time the recording light on the camera blinked. I thought this might be some kind of signal leakage to the headphones, but it’s also there on the computer timeline. Quite noticeable because the background is very silent. We did spot this problem on just one of our field shoots.

This sound is not there when using the internal mics on the camera, nor is it present when using a shotgun mic. If I attach the radio transmitter via a long audio cable there is no artefact ie when the transmitter and receiver are 4 metres away from the camera. I’ve tried three different radio frequencies but still get the problem. I’ve also tried two different transmitter/receiver units – same issue.

Now, I can fairly effectively remove this artefact using noise reduction in Sound Forge, but I’d rather it wasn’t there in the first place. Any thoughts?

David S

Comments

JackW wrote on 8/1/2014, 11:55 PM

What happens if you turn off the tally light on the camera?

Jack

musicvid10 wrote on 8/2/2014, 8:23 AM

I would suspect shielding issues in the receiver or noise suppression in the camera.
Sounds similar to cell phone interference in audio gear; can be tough to tame.

If a fixed camera location, a tabletop receiver has better shielding and is away from the camera.

[Edit]
Does the problem go away instantly if you break contact between the receiver and camera shoe?

rraud wrote on 8/2/2014, 9:16 AM

Have you tried switching to a different frequency/channel on the wireless system. Is the receiver's output unbalanced? Could be getting in though the cable.

imaginACTION_films wrote on 8/3/2014, 5:42 PM

Thanks for the ideas - turning the tally lamp off doesn't help. The flashing light is the Access Indicator which pulses assess data is written to the internal memory.
I am using good quality XLR connectors. Normally the receiver is attached via the cold shoe with a short XLR cable going to the mic input on the camera. This is when I hear the pulsing.
If instead I connect the receiver via a long XLR cable, and then walk away with the camera while recording and monitoring in headphones, the artefact decreases with distance until at about 2meteres distance it's pretty much gone.

I should say I've never had this problem with other cameras such as a Z1, A1 or PD150.

I think I'll proceed by
a) getting the camera checked under warranty, and
b) using the receiver with a longer cable placed away from the camera. Not ideal, but it works.
Thanks - David S

imaginACTION_films wrote on 8/3/2014, 5:45 PM

I should add, yes, the output is balanced, and yes, I have tried several different widely divergent frequencies, and also two different transmitter/receivers.
Frustrating issue because it's so convenient to have the receiver sitting on top of the camera. Ah well, life in the digital age...

musicvid10 wrote on 8/3/2014, 6:15 PM

Maybe put metallic tape over the indicator?
Might shield some of the interference?

imaginACTION_films wrote on 8/3/2014, 7:39 PM

Good idea, musicvid.

Tried the radio mic with the Sony Z1. Absolutely silent.
Also tried it in my Pentax K5-II. Absolutely silent. So it is something to do with the Canon. Time for a check under warranty.

rraud wrote on 8/4/2014, 9:37 AM

Some kind of RF spill from the camera and poor shielding at some point on the wireless.
I've never encountered that problem with Lectro or Sennheiser systems and had them on many different cams. (but not the Canon XA10)
I've heard the chirping sound from cell phones and such, but not using my own gear and cables.