RF noise

[Rick Moss]

Hi all; I’m hoping you can help. I have searched the forum and seen many posts about RF noise, but none quite match my issue:

Whenever my Skyview is turned on, there is a constant hum heard through the headsets. It is not affected by adjusting the volume on the radio, and it is not breaking the RX squelch. If I pull the breaker on the SV, the volume drops slightly, but the hum remains as it runs on the backup battery. Turning the SV off completely stops the noise.

It’s a composite aircraft, with all grounds run to the same negative bus bar, itself connected to the battery via 4AWG cable. The Dynon and the radio receive power from 2 different busses, although these busses are connected together with a Schottky diode between (1 is for Essential Services,

Fitted system:

New SV1000 installation, with an existing Trig TY91 radio fitted, connected to the SV via a serial TX/RX and the Audio-out runs to the aux-in of the Trig.
I am using the intercom built into the Trig; this radio has performed perfectly for the last 6 years with the steam gauges.

I’d be grateful for suggestions of where to start!

 

[Raymo]

Have you adjusted the radio and intercom squelch?

 

[Rick Moss]

I have; neither make any difference.

I have now discovered that the hum gets louder as the screen gets brighter, and quieter as it goes dimmer.

 

[Raymo]

Try grounding the screen(s) directly to the intercom. If that doesn't help, contact Dynon support directly. BTW, I prefer all audio related grounds going to a single point/location that is then grounded to the main aircraft ground.

 

[Rick Moss]

They’re both grounded to the same bus bar; so within 2” of each other on the same piece of brass: would screwing them on with the same screw make a difference, or are you referring to linking the 2 grounds elsewhere? I presume this would create a loop, which I understand to be a bad thing.

 

[Taigajoe]

Hello Rick,

I have the same problem with SV700 connected to the auxiliary input (AF_AUX_IN_HI) of an radio Becker AR6201 . If I disconnect the auxiliary input or if I use DIM level above 15 then the hum disappears.
The radio and the SV700 are grounded at the same negative bus bar. I think the brightness of the screen is regulated by PWM.

And I have another noise on the audio output of SV700: I have an irregular crackling on the line. For my understanding are these spikes radiated by data packets transferred somewhere in the system.

Has anyone this irregular crackling too?

 

[Stevec]

Hi

I have a D1000 and D700 with the audio outputs connected to a PM1200 intercom. I found that I heard a background noise that I could not remove. All grounds go to a common point. I also read in the installation manual that connecting the units case directly to ground with a 16 g wire would help with electrical noise. Nothing seems to work. I have discovered using the isolate switch on the PM1200 removes the noise and reading how the switch works I am now certain that the noise is being introduced into the system via the audio lines from the Dynon units. However I don’t yet have a solution to the problem

 

[Raymo]

They’re both grounded to the same bus bar; so within 2” of each other on the same piece of brass: would screwing them on with the same screw make a difference, or are you referring to linking the 2 grounds elsewhere? I presume this would create a loop, which I understand to be a bad thing.

Not exactly. A ground bar/location for all audio related components that is then grounded to the central ground location/battery. No ground loop will occur.

 

[skyboy999]

I seem to recall this was a known issue some years ago and Dynon provided an EMI kit to help suppress.

 

[airguy]

I seem to recall this was a known issue some years ago and Dynon provided an EMI kit to help suppress.

I remember one for the EMS units, to prevent RFI from wiggling some sensors like EGT/CHT, but I don't remember one for the display brightness. Might have been before my time, I picked up my hardware in 2014.

 

[Taigajoe]

I seem to recall this was a known issue some years ago and Dynon provided an EMI kit to help suppress.

I installed this EMI kit several years ago. If I remember right than I did not had this massive crackling after installing th EMI kit. Is it possible that this EMI kit is out of order?

 

[fastfred58]

Did you ever get this figured out. My d1000 is doing the same thing . I turn the skyview off and the garmin radio works fine.