RF Interference with VX2100 and DXA8 at DVinfo.net

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Sony VX2100 / PD170 / PDX10 Companion
Topics also include Sony's TRV950, VX2000, PD150 & DSR250 family.

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Old June 17th, 2006, 04:54 PM   #1
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RF Interference with VX2100 and DXA8

Well I just received my new Beachtek DXA8 to use with my vx2100. Unfortunately, I've been having problems picking up a radio station on my XLR mic cable. Whenever I plug in my 1.5ft XLR cable in the input of my DX8 (either hooked to my mic or floating) I very clearly pick up a radio station. It doesn't matter if the XLR cable is connected to anything or not and if connected to a mic I simply hear the RF in the background. Obviously my XLR cable is acting like an antenna. Strange, huh?

I've been working with Harry at Beachtek who has been very helpful. I checked to make sure the I have a good common ground between the camcorder and the DXA8 adapter. I've also tried both ground switches on the DXA8 with no luck. I've also checked to make sure pin 1 on both ends of my XLR cable have a good connection into this common ground. None of that made any difference whatsoever. Other than this issue the DXA8 seems to be working very well. Although the noise from the internal vx2100 preamps is still unacceptably high and I'll definitely be going with a line level preamp like the DXA10.

The only thing that I've done that has made any improvement to the RF interference problem is to wrap my XLR cable in aluminum foil and then ground that to the camera chasis ground. Doing that cut down the RF interference to maybe half but it's still very noticable. To me it just seems as though the DXA8 is doing what it should and it's just amplifying the signal on the input which just happens to be an RF signal on the XLR cable/antenna. So I'm thinking maybe is something wrong with my cable? It's the 1.5ft XLR cable that came with my Rode NTG2. I've taken apart each end piece and the shield wire seems to be solidly connected to pin 1. I'll probably buy another XLR cable soon and try that.

I'll be getting another DXA8 along with a DXA10 on Wednesday so hopefully I'll have better luck with them. Honestly, because of the high noise level when using mic levels I'm pretty sure I'm going to go with the DX10.

Has anyone ever had an RF problem this bad? I expected this with my wireless setup but not with my wired XLR system. Quite strange. We live in some mountains west of Tucson,AZ kind of out of the city. There are a bunch of radio towers on a peak behind us but they look to be about 3-4 miles away and well above us.

Luckily, we're I'll normally be filming (remote Alaska and Africa) there's little risk of radio interference but I'd like to use the system at home too with having to listen to rock music in the background.

Any suggestions?

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Old June 17th, 2006, 04:58 PM   #2
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the only suggestion that would really work would be to return the box to the seller for exchange.
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Old June 17th, 2006, 05:53 PM   #3
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Like I said the problem doesn't appear to be with the box. I'm going to try ordering a quad xlr cable which is alot better at RF rejection than a standard xlr cable.

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Old June 18th, 2006, 04:42 AM   #4
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Hello John,
Use a good multimeter to rule out any high (or low) resistance connection between pin 1 and and the other two pins in the XLR cable.

If the cable is good, It's the BeachTek. This is a classic case of "Pin 1" grounding error--a design issue. I think you (or Harry) will find the the XLR shield is connected to a circuit board or some other common point, and then there is a little pigtail grounding the circuit board to the the chasis. There is enough impedance in the pigtail at RF frequencies--although it's fine at audio frequencies--to be an antenna to broadcast the signal carried in by the XLR shield to the world INSIDE the chassis. You can google this to learn more. The cure is to ground XLR pin 1 directly to the chassis.
[Edited to correctly state reason for pigtail impedance]
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Last edited by David Ennis; June 18th, 2006 at 05:31 AM.
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Old June 18th, 2006, 06:59 AM   #5
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I have a similar problem with a mixer. The Shure A15RF RF Filter solved the problem. Full Compass has a pretty good price.

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Old June 18th, 2006, 08:26 AM   #6
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I doubt that it is the Beachtek.

I say this because I have a problem with RF interference and my VX2100E (which first came to light when I bought a DXA-2S but as it turned out the DXA-2S only made me aware of the problem - it was not the cause).

Basically when ANYTHING is plugged into the external mic/line jack I can quite clearly see the level meters jumping up and down even with no audio being present i.e. just plugging in a 3.5mm jack plug with no wiring simulates the problem and the actual sound being produced is sort of 'static crackles' (and this is recorded by the camera as well).

The strange thing is that it only happens as certain physical locations on my premises and is even directional i.e. it depends which way the camera is pointed. There is no problem at other physical locations (like down at the beach).

The camera has been to Sony for this and they actually performed the PD170 audio modification for me which reduced the famous VX2100E background hiss and, to a certain extent, this modification also lowered the level of the 'crackles' described above but did not eliminate the problem.

This problem occurred long before I discovered dvinfo.net so there is an extremely long explanation of the problem as well as my testing and results thereof of another bulletin board. We are not supposed to place links to other boards on this board so if you email me I will send you the links if you are interested. You can use dpaterso@videoproductionssa.co.za.

If there is a point to me copying all of that information over to dvinfo.net then I will glady do it but need input from the dvinfo.net users.


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Old June 18th, 2006, 12:15 PM   #7
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It is unreasonable to plug any unterminated device into the microphone input and not expect the conducted noise level to increase. If you short the input, that is the proper way to measure the self-generated noise of the camera. You can short the far end of any cable that is plugged into the camera to measure the noise level of the camera and any induced by the cable.

Once you conduct noise inside the camera with an improperly terminated or shielded cable, the game is over because the camera doesn't have (and cannot have) internal filters to stop the propagation of the noise throught the audio chain.

In addition, this class of Sony cameras we use are known to be susceptible to RFI/EMI noise. Sony even replaced my PD150 because of its problems in the presence of high-powered radio transmitters such as those found in police cars.

It is not surprising that even with well-shielded cabling, the external XLR boxes capture and deliver noise to the microphone input of the camera. That's one of the reasons I chose a PD150 over the VX2000.

Another known problem with the 2000/2100 is the propensity of the 1/8" mini-socket to deform and lose good ground contact when the external jack is deflected enough to bend the socket internals (and it doesn't take much). That problem will generate noise too.

The best way to combat this with an external pre-amp is to insure that the camera audio levels are turned down and the external pre-amp's gain is up. That way the noise imposed on the input circuitry of the camera is much lower than the input signal and won't be amplified as much as if the camera/pre-amp levels relationship were reversed.
Mike Rehmus
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Old June 18th, 2006, 05:22 PM   #8
Fred Retread
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Originally Posted by Dale Paterson
I doubt that it is the Beachtek...
Believe it. Your doubt is based upon your experience with an entirely different situation.

If you're picking up an AM radio station with a device that is supposed to be sheilded by its metal housing, that device has the pin 1 grounding error I described earlier.
"Nothing in the world can take the place of persistence..." - Calvin Coolidge
"My brain is wired to want to know how other things are wired." - Me
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Old July 20th, 2006, 04:21 PM   #9
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DXA-8 RF issue

At one of my client's sites I used to get intermittent RF pickup issues when using my DXA-8. I found that I either had to hold the unit in my hand while shooting, or re-orientate the unit until the RF disappeared.
I have since upgraded to a SD302 mixer and have had no further RF issues even when I'm back shooting at the same client's location.. I also have StarQuad and Klotz cabling; cables didn't seem to make a difference; changing mixer certainly did..!
Rgds, Ross.
XH-A1; HV-20; Miller DS-10; Manfrotto 695/3229; SD302/702; PCM-D50; FCS2; MacPro; 2.25TB
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