Strange Ammeter Readings

[jiott]

I have a Dynon Skyview in my Kitfox with 912ULS engine. I use the Dynon EMS (engine management system) module with all Dynon supplied engine sensors for the Rotax engine. The amps sensor is a Dynon supplied shunt feeding into the EMS module. My amp readings on my Skyview engine page are always normal and consistent EXCEPT for one situation: When I press the push-to-talk button to transmit on my Garmin SL-40 radio, the amp readout goes wild showing negative values winding up to 40-50 amps! Of course these values can't be real and I have ignored them for 2 years now. It has done this since day one, and the readings immediately go back to normal after I quit transmitting on the radio. No breakers ever trip and no smoke or damage of any kind has occurred.

I submitted this "problem" to the Dynon tech support people and they think it is due to the RF energy from the radio interfering with the very sensitive ammeter sensor wires (unshielded). The sensor uses only a few millivolts/amp. My radio antenna is mounted on the bottom of the fuse and I use the hi quality RG400 coax cable from radio to antenna. This cable does run within about 6" of my EMS module. Dynon suggests I try moving the antenna cable routing farther away, but I am hesitating because it is not an easy job and that cable is very well shielded.

So here is the question for you electrical gurus out there: Have any of you heard of this before or known anyone who had to deal with it? What did they do, or what would you do. I am very strongly inclined to continue to ignore it as I have been for 2 years. Do you see any potential problem with doing that?

[Av8r3400]

Do your push to talk leads pass near the shunt?
Does the antenna lead pass near the shunt?

What does pass near the shunt for wiring?

[Av8r_Sed]

This could be a good application for a snap-on ferrite bead located on the sense lines near the shunt. They kill RF while letting low frequency signals pass. image.jpg

[jiott]

The PTT leads do not pass anywhere near the shunt. The radio antenna cable also does not pass near the shunt. The items/wiring that are near the shunt are: voltage regulator, transponder and its antenna cable, capacitor.

Where do you get the ferrite beads/what brand are they-looks interesting.

[kitfox2009]

G`morning Paul and others

I have Vixen 912UL. All older round gauges. A210 radio and Terra transponder. Avshop after market Lightspeed headsets.

Occasionally I get feedback when on transmit to the point that radio is unusable. I try an old DC and all`s well. Then go back to my Lightspeed and all`s well. When flying last week with a friend and 5 headsets, kept changing them around and everything was fine. (the Bose won, hands down!!). Anyway just wondering if these "ferrets" would help this situation and if so does anyone have an idea as to what type and where I would place them.

Radios and headsets are a total mystery to me and there appears to be quite a bit of knowledge and experience on this forum.

Right now everything is just fine but you never know "it just might start squealing" again. May not happen til next year.

Thanks
Don

[kitfox2009]

That should "ferrite"

[jiott]

I installed two ferrite toroids and it didn't make any difference. I have just been living with it; it hasen't seemed to hurt anything.