Matronics Email Lists Forum Index Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
 
 Get Email Distribution Too!Get Email Distribution Too!    FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Radiated Electronic Noise (not a grounding issue?)

 
Post new topic   Reply to topic    Matronics Email Lists Forum Index -> AeroElectric-List
View previous topic :: View next topic  
Author Message
noel.wade(at)gmail.com
Guest





PostPosted: Sat Dec 16, 2017 5:22 pm    Post subject: Radiated Electronic Noise (not a grounding issue?) Reply with quote

Hello All,  
I'm hoping for suggestions from the experts here, as I'm stumped at how I might alleviate a problem with what I think is *radiated* EMI that's making its way from my EFIS into my VHF radio system (i.e. over the air, received by the comm antenna). And so far the manufacturer has been unresponsive to my support requests. Sad
  
Here is a video demonstration of the issue, using a handheld radio (to try to show that this is not a ground-loop or other issue with the wiring of the panel-mounted VHF comm system): 
https://www.youtube.com/watch?v=kg8bZ5wZ3bk

  

After recording that video, I tried placing a piece of sheet-metal in front of the antenna (to block line-of-sight from the EFIS) with the sheet-metal grounded to the airframe. I can clearly demonstrate a change in the amount of received signal when the sheet-metal is removed from blocking LOS, by observing the reception-strength bargraph built into the VHF radio. This to me reinforces the idea that this is some kind of electromagnetic field/radiation that's the problem, not induction along a wiring path. But I'll admit that I'm a novice when it comes to EE stuff; I usually work in the digital realm with computers and networking, far from oscilloscopes and the analog world of volts and amps.
  
Any thoughts or recommendations for how to proceed, how this issue might be confirmed, and/or how it could be alleviated, short of replacing the system**?  
  
Thanks so much for your knowledge and ideas!
  
--Noel Wade
noel.wade(at)gmail.com (noel.wade(at)gmail.com)
Seattle, WA
  
-----

Background info, for the interested: 
-----  
I _can_ run the squelch up very high in order to not have the panel-mounted VHF radio think its receiving a valid signal. But that severely limits my reception range overall. I've done testing with various items in the aircraft powered off (and with fuses removed), and the problem only occurs when my EFIS is powered on - as evidenced in the video. And again, this issue occurs with handhelds as well as the panel-mounted radio.
  
To be clear: This is *not* an issue with noise or feedback in the headset. This is the radio actually thinking its receiving a signal and breaking squelch. The panel-mounted radio was previously used in my sailplane and worked just fine (at a much lower squelch value). And it works just fine at a low squelch value with other aircraft items powered on and the EFIS "cold".  Other aircraft on the ground at my local airport report my radio transmissions as loud-and-clear, so outbound transmissions seem unaffected.

  
For power and ground, all equipment in my panel is wired in using twisted twisted pairs: Each supply line comes from a fuse block, and each ground wire goes to a "forest of tabs" on the stainless steel firewall with a large-gauge wire connected back to the battery. Signal wires are almost exclusively run through wiring harnesses provided by the manufacturer, using shielded wires and a twisted-pair CAN bus wire or RS-232 signals (again on a shielded wiring pair). The comm antenna is connected to the radio using RG-400 coax and the coax is run at least 6" away from the (shielded) headset and microphone wires. 
  
Photos of my aircraft build (including some shots of the wiring) are here: https://flic.kr/s/aHskrtEG22
-----

  


- The Matronics AeroElectric-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List
Back to top
user9253



Joined: 28 Mar 2008
Posts: 1907
Location: Riley TWP Michigan

PostPosted: Sun Dec 17, 2017 8:13 am    Post subject: Re: Radiated Electronic Noise (not a grounding issue?) Reply with quote

If MGL were made aware of your video, they might be more responsive to your support request. That video must be hurting their sales. It looks like the EFIS needs to be repaired. Another experiment would be to wrap tinfoil around the top and front and bottom edge of the instrument panel wide enough to cover the EFIS. That experiment would reinforce your theory that RF noise is being emitted from the EFIS screen. Have you tried dimming the EFIS display to see if that has an affect?

- The Matronics AeroElectric-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

_________________
Joe Gores
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Matronics Email Lists Forum Index -> AeroElectric-List All times are GMT - 8 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


Powered by phpBB © 2001, 2005 phpBB Group