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Old 11-22-2019, 08:17 AM
DennisRhodes DennisRhodes is offline
Join Date: Jul 2007
Location: Taylorsville, Ga
Posts: 767


The shields are properly terminated at the jacks but I haven't verified the tray connector yet. [/QUOTE]

Just a quick verification that your shields are UN terminated at the jack and only at the shell at rear of tray. By " properly terminated" you mean UN terminated and shrink wrapped I'm thinking. Generally shields are ONLY terminated on one end. Just my observation in a quickly read of your post . Hope you are able to find that problem, those can by quite annoying AND hard to find. Best of luck forward.
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Old 11-23-2019, 08:33 AM
clam clam is offline
Join Date: Oct 2005
Location: Lakeland, TN
Posts: 193
Default A16 manual ?

I could not locate the A16 manual on the MGL website. Can you provide a vector?

Originally Posted by Rainier Lamers View Post
Many years of assisting customers with audio problems related to intercom systems, headsets, radios have resulted in some experience.

However, recently, I struck gold, quite by accident.

In the past I used to recommend simple small audio transformers to break the ground loop issue. You can get them inexpensive - typically the 1:1 600 ohm types often used in phone line systems.

Then I started using a Bourns SMD type (SM-LP-5001 - you can get from Digikey in small quantities) as I wanted something smaller you can easily incorporate in an audio cable with a bit of shrink sleeving over it. This thing worked very well indeed but I noticed it was particularly effective with RF induced problems - normally the audio transformers tend to just couple RF without much advantage here. This one effectively blocks it totally.

Even better - you can wire it as common mode choke into headset microphone feeds (it's small and can be wired right into the mic socket). In this mode it conducts DC so the MIC still gets its bias current, audio passes as differential signal unaffected, any common mode noise is attenuated and even better - RF is blocked as the core material handles it quite nicely.

It's the solution to pesky RF feedback problems in compromised installations.

I devoted a chapter to how to use them between intercom systems COM outputs and radio MIC inputs as well as into standalone radio/intercom systems into the headset MIC feeds in the A16 manual you can get from our website. The manual is dedicated to out A16 but the solution is applicable to any make of intercom system and radio so if you have some issues in this area - give it a read.

CEO MGL Avionics
Memphis, TN
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Old 11-23-2019, 08:50 AM
moosepileit moosepileit is offline
Join Date: Dec 2010
Location: Floyds Knobs, IN
Posts: 605

Found it in this doc, page 7 on.
RV-6, bought from builder.
O-320, slider, carb, mags, FP

Last edited by moosepileit : 11-23-2019 at 09:06 AM.
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Old 11-23-2019, 08:52 AM
jliltd jliltd is offline
Join Date: Sep 2013
Location: Rancho San Lorenzo
Posts: 800

Rules of thumb:

For shielded audio circuits (like headphone jacks), have phone and mic jacks insulated with plastic shoulder washers, terminate shielding at this end as "open" without connecting to anything (just heat shrink the to insulate the cutout end). On the other end have shielding bonded to audio source chasis (audio panel, intercom or comm backshell depending on configuration) with a shield drain solder splice. If the shielding or jack barrels were grounded at the headset end that is bad as there would be a propensity for noise caused by an electrical ground loop.

For non-audio circuts: Shielded data wires between avionics (like RS232, ARINC 429 etc...) connect the shielding at both ends, to each respective component chasis (backshells). In the case of CAN Bus the philosophy has changed over time and currently says to connect shield drains at every node component backshell.

Last edited by jliltd : 11-23-2019 at 09:49 AM.
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Old 11-23-2019, 09:24 AM
lr172 lr172 is offline
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 4,965

Originally Posted by majuro15 View Post
My remote audio panel doesn't work like that. In ISO mode, the pilot is isolated and has no side tone unless transmitting on a radio. The three other seats are all intercom connected and cannot hear radio traffic at all.

In Crew mode, the backseaters are intercom only and the front seaters are intercom between themselves and radio.
I would argue that in ISO mode, the pilot headset has a direct connection to the radio at all times and the silence is due to the radios squelch circuit blanking all transmit volume, though power is still on the wire and therefore subject to noise. Put yourself in ISO mode and turn off the radios. If the noise goes away, you can assume the problem is between radios and intercom. If it doesn't, you can assume it is likely in the headset circuit or other intercom issue.

EDIT: Just realized that turning off the radio won't eliminate all issues on that circuit, but should isolate some.

If headsets get the noise in normal mode, but not in ISO mode, your issue is likely in the int to radio circuits. If you can make the noise appear in the passenger headsets without someone else breaking intercom squelch, you issue is not in the pilot headset circuit.

N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019

Last edited by lr172 : 11-23-2019 at 09:31 AM.
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Old 11-25-2019, 02:49 AM
Rainier Lamers Rainier Lamers is offline
Join Date: May 2007
Location: Somerset West
Posts: 1,027

Originally Posted by moosepileit View Post
Actually, have a look at page 43. Shows the two ways of using it in a more generic way.

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Old 11-25-2019, 07:35 AM
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9GT 9GT is offline
Join Date: Jan 2010
Location: Southern Michigan
Posts: 1,887

When I started flying my RV-10, I had a headset whine whenever the nav/position lights where on. I tracked it down to my home rolled LED tail position light. I used a low cost power puck. Replaced it with a better more expensive one and that took care of it. Hope you are able to get your noise problem solved.
David C.
Howell, MI
RV-10: #41686 Under Construction
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RV-10: #40637 Completed/Sold 2016
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Old 11-25-2019, 01:01 PM
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majuro15 majuro15 is offline
Join Date: Feb 2013
Location: Charlotte, NC
Posts: 655

Larry, you were right. So I was correct in how the ISO modes work, but realized that the ISO isolates the radio from the other headsets. I spent four hours tracing and shooting wires all to figure out that no ground issues exist and I should have investigated the easy stuff first.

I've come to the conclusion it is the ZipTips interfering with the radios. The radios are actually RX in sequence with the strobes, and at all times with the Land/Nav lights on. The Avidyne does a better job of filter it out, but you can still hear it with the squelch turned on. The Dynon radio can't filter it out. I even double checked all the antenna coax and everything is wired correctly.

I know Aveo had to replace the Gen 1 light modules due to this issue, so I have a message into Damien. Hopefully I'll hear from him this week and get the new modules soon. Right now I can fly with Comm1 and lights, but it still makes the radio scratchy.

Thanks for all the help!
Tim Huneycutt, Capt, NCANG
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