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It seems that Dynon is fighting an electro-magnetic interference problem (EMI). Hopefully it won't be too hard for them to solve. The following message was posted on the RV-List (the first part is a question from a list-member - the second part is a response from Sam Buchanan):

>>I recently flew my RV7 from Fl to Spokane and back and still >>love my Dynon D-10. I do however have a problem that concerns >>me: the D-10 emits enough RFI to render the VOR/LOC receiver >>inoperative unless within approx 7 miles of the station. The >>VOR voice is nothing but static. Turning the D-10 off >>rectifies the problem and the VOR will receive up to 100 NM >>away. I have a wingtip mounted VOR antenna.>>>>Dynon said they have had several complaints on this problem >>and are working on it. I was wondering if anyone on the list >>has had a similar problem and fixed it and if so how.

Yes, I have been dealing with the EMI issue with the Dynon. Like you, I am very impressed with the D-10, but the initial install was a bit challenging. One problem had to do with a bad magnetometer and has been successfully resolved. The other issue which is still present but now very manageable, is the EMI emitted primarily via the EDC remote magnetometer serial connection. I doubt that antenna location, radio stack location and other such physical items are going to have much impact on whether or not EMI is present in a particular Dynon installation.

It appears the EDC is transmitting considerable RFI back up to the D-10 via the EDC power feed. The noise then is passed along by the D-10 out the main power and keep-alive feeds to the avionics bus. EMI is a very strange and unpredictable animal that often flaunts logic. In my case, the noise was very noticeable through the com radio, even to the point of often breaking the squelch. But, it wasn't consistent; even though always present, it varied depending on the frequency in use, the time zone I was in, and what I had eaten earlier in the day. In other words, there was little pattern to the madness. The nav side of the radio was completely unaffected.

After some basic troubleshooting (disconnecting the EDC while the D-10 was running) it was determined that the EDC was indeed the culprit. Doug at Dynon was working through the problem and suggested I power the EDC via a different point on the avionics bus. That I did, and the noise was drastically reduced. As a part of Dynon's troubleshooting, I also installed some capacitors in the D-10 and the EDC and that lowered the noise level a bit more.

Bottom line, at this point in time there is still a very low amplitude noise in the my com radio which is only noticeable when receiving very weak signals. The separate power feed for the EDC "solved" most of the EMI problem. But the Dynon guys realize this is not a true solution since now the remote mag is isolated from the back-up power features of the D-10, and the EMI is still being generated. Also, the separate power feed can create some weird issues when using the support program to customize the EFIS. It is necessary to interrupt the power to the EDC when the D-10 is rebooted or the support program can hang since the EDC is still in a "Loader" mode.

I suspect there are many Dynon installations that have the noise issue but the builder doesn't know because the source of the noise is buried in the chaos of getting a new panel up and running and the builder is chasing all sorts of shielding ideas trying to figure out where the static is coming from. By the way, one of the first steps I took was to replace the CAT-5 cable I was using for the remote mag with four-conductor shielded cable, but that had no impact on the problem. I also shielded the main EFIS power cable but that likewise had no impact.

So shielding does not seem to be the answer, and the EMI bug will affect some installations and not others until Dynon gets a handle on the problem. If nothing else, the remote mag can be disconnected and the "problem" goes away (along with a *very* accurate heading indicator if the mag installation is carefully done!).

In my opinion, this in no way should be a discouragement to buying a Dyon EFIS. The unit works as advertised, and I am very confident the Dynon crew will squash this bug and do what is right to rectify the situation for those who find it necessary.

John, try the separate power feed for the EDC and your nav will probably again be usable.

Sam Buchanan

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