RF Noise when running of external battery

[Jeff_R]

I am completing my RV and have noticed the radios break sqelch all the time. A radio shop did my wiring and panel installation, and I had complained to them about the noise but they haven't done a thing. So, last night I did some troubleshooting, thinking the problem was due to some LED strip lighting which despite an apparent on/off switch, never was turning off - it just went very dim.

Instead, I found that the pilot-side Skyview (I have a dual 10" installation with dual backup batteries and dual ADARHS) was generating the noise. The noise would start a couple of seconds into the boot sequence after the DYNON word came up. If I then power the system down via the power switch on the panel, the noise immediately stops even though the system will continue to run off of the backup battery. If I switch the main power back on, the noise immediatly comes back. So, when the display runs off main power, it is noisy. When it runs off its own backup battery, it is quiet.

For the co-pilot side display, there is no noise. However, that display is not recognizing its backup battery, which I suspect is bad. It is connected, but the system doesn't see it and reports 0 volts.

Do you think I have a grounding problem? Seems like I have a bad backup battery as well.

My radio shop has not been very supportive, even though they are on-field. I just want to get some ideas on what the problem might be in case I have to fix it myself. Oh, and the system isn't showing either of my autopilot servo's as being connected, even though the cables are connected. Again, no radio shop support.

Thanks for the help. I can't wait to fly with this system!
Jeff

 

[dynonsupport]

Some early SkyView displays did output more noise than was ideal - though it was still within limits for certified applications, which we don't need to meet, of course - and for those customers we have filters that may help improve things. Later units did not have this issue as we built the filtering built into those units. So first question - what are your display serial numbers?

Also, below is a repost of information we shared about RF emissions from a while back that explained the whole picture as we were working through this issue:

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We performed tests at a fully certified lab that Boeing (we're in the Seattle area) also uses. SkyView meets/exceeds RTCA DO-160F, category H, for aviation COMM, NAV, and GPS bands. Cat H is the hardest to pass, for devices that are in direct view of an antenna. We did our tests with a full SkyView network with long cables, modules, servos, GPS antenna, battery, etc. As some of you have found, the display by itself is "quieter" than a whole network, but the whole network does pass including all accessories and wiring.

Certification requirements do allow some noise output. No electronics are silent, and the standards do have noise limits. This is why you will see squelch level differences when you have a SkyView on vs. off. We're by no means claiming it does not output RF noise at all.

We have also tested a D100, and it also passes by a substantial margin. We have never heard of EMI issues with a D100, so it appears that some customer installations are more sensitive than the FAA requires.

RF interference can be a hard issue to track, and wiring configuration, antenna location, antenna ground-plane, and general dimensions and construction materials of the airplane can make a big difference. Even manufacturers of certified planes struggle with these problems. So we're thinking that some installations are more sensitive than others, which is why not every customer is experiencing issues.

We do a lot of work on EMI, and as proved recently, we do pass the certification requirements for avionics. Even though that is true, we're committed to making SkyView work well for everyone, so we'll continue to work on improvements, including hopefully some hints on wiring practices that may help a lot.

Just the same, the good news is that we lab-tested and field-tested filters that are simple plug-in devices on the D37 and D9 connections (for use on early SkyView displays only) that offer a large amount of noise reduction. It performed in the field as well as it worked in the lab, solving any noise issue, and we should be able to offer it shortly. Newer SkyView displays have this filtering built into them already.

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[Jeff_R]

My serial numbers 2171 and 2145.

Thanks.

 

[dynonsupport]

Given those serial numbers we have filters that should help the issue. Give our tech support staff a call at 425-402-0433.

 

[Jeff_R]

My radio shop obtained the filters and installed them and they got rid of the noise on the Garmin SL-30. For the Icom A-210, I can turn the squelch down from 8 to 4 now (on a scale of -10 to +10). Still maybe a tad high, but I think it will be acceptable.

Thanks for the support.
Jeff