I occasionally shoot news - not often.
I got a call to cover a large fire (Melbourne, Australia) which was attended by at least 12 fire units, many police, media and back-up etc.
Everything was fine until I grabbed my audio gear for a stand-up report (which thankfully never eventuated).
I was using a Rode NTG 2 with a Sennheiser plug-in transmitter going to a receiver attached to the XDCam PMW-350.
I experienced some serious audio artifacts which I would call 'cavitating' or 'pumping' - the signal fluctuating between clear and crap. I assumed that I was on a frequency that someone else was using so I tried a couple more. No luck. So I used the clever frequency scanner on the Sennheiser receiver to find a clear frequency, and chose it. Still no luck.
I tried the same mic through an XLR lead and it was fine. When I got home I tested each of the components and they all came up fine.
It seemed to me that the camera itself was being effected by something nearby.
Has anyone else experienced this? Or maybe I just didn't try enough frequencies?
Although the mic and the transmitter were new, I've used thus set-up many times before.
I shoot news with a Sony EX-3 and have the same mike set up that you have (but use a Senn 416 with power adapter/Senn G-3 block A) and sometimes I get the same effects...I change the frequencies using the scan function and I get the same thing...so I have to go hard wire....But I am always around the fire trucks or police cars...and they might be doing something to the frequencies.
But as you did, when I got home I did a full test of everything...I even had my daughter walk down the block of my neighborhood...with the shotgun mike in hand, going about 150 ft....I had her do the same thing again, but this time I had the plug in transmitter connected to a Shure RE-50 hand mike....