A7s RF Interference Issue

[bodressler]

 I have been using the Sennheiser ew g3 100 system with my a7s for nearly a year now.  Generally, with the receiver not mounted on my rig I get decent results, but with it mounted on the rig I have lots of interference problems.  However, I've used other Sennheiser systems with other a7s rigs flawlessly (albeit not mounted to camera) (30 interviews in 3 nights with not one RF hit). I've used this system with c300, mounted to camera, no RF hits.  

After a call to Sennheiser tech support we determined that my particular camera was acting as an RF antenna that was causing the afore mentioned interference based on this test:

-Just camera and cage set up and turned on. Receiver turned on. Receiver exhibits a little bit of RF on the display. When moved away from camera RF goes down and then out completely

-Camera, cage, rails, monitor and shotgun mic attached, same behavior only more RF is present when the receiver is close to the rig than before. 

-With the same setup as above, I scanned a new list with the receiver mounted to the camera with squelch on low. No free channels usable. 

My question is: are there any a7s users who have had this problem before? Is there a setting on the camera that I can change to stop this from happening (it's on airplane mode already)? Do I need to get a new camera??? This happens regardless of what monitor is bolted to the rig, and I have also in the past noticed strange feedback on sound coming from my rode videomic plugged straight into camera as well (although this does not consistently happen).

I want to be able to mount the receiver on or near the camera like I am supposed to be able to and (within reason) not have to worry so much about it!

Thanks for your advice in advance!

[bodressler]

OK check it out.  I got to the bottom of the problem but now I don't know how to solve it. 

After systematically taking apart the rig and checking how the receiver behaved after the removal of each individual component I finally got to the last three bits:  the camera body, the metabones speedbooster, and the canon 24-105.  With all three together there was the same RF behavior as before, but after the lens was removed, the RF dropped off and there was no longer an issue!  I've also noticed that when the camera is powered on and the lens "engages" there is an RF spike and then it returns to about 1/3-2/3 filled on the display.

Any ideas?  

[tupp]

More details would be helpful, such as what type of interference are you experiencing (static noise, distorted signal?) and what bands/frequencies have you manually set.

 

However, it sounds like your camera/lens combination might be generating weak, spurious EMI (electromagnetic interference) that your receiver is picking up due to proximity.  If so, changing frequencies/bands might help.  If the housing of your receiver is plastic, you might try wrapping the housing with metal foil as a test to see if it reduces the interference (leave a small space between the foil and base of the antenna).  By the way, RF means "radio frequency" -- not necessarily "interference."

 

It appears that others have had problems with the EW100 G3.  If nothing else works, you might try using a spectrum analyzer to see if the camera rig (or some other source) is generating EMI.

[bodressler]

Thanks Tupp!

The characteristic of the interference is static noise, or it comes in the form of a "hit" which is more of a short static burst.

I've done further testing today.  All metabones adapters connected to canon zooms (speedbooster, speedbooster ultra, and electronic regular) with 24-105 (2 copies), 24-70, and 70-200 create distinct RF changes on the reciever, with the 70-200 being markedly better that the 24-105 and 24-70.  Also tried turning off/on IS and AF to no effect.

Native Sony lenses no issue.

Canon 15mm no issue when connected to speedbooster.

Tokina 11-16 no issue when connected to speed booster.

Getting to the point where I'm thinking it might be smart to try the sigma 24-105 to resolve the issue and keep generally the same set up.  Frankly it seems like a bizarre workaround though and I'm surprised other people haven't reported this issue before?