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Alternator noise


Tom Baker

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I'm having the same problem with noise from the GPS. I didn't have time to really look for the issue yet, but you gave me some ideas.

 

Also, you know there are settings in the x96 series for the speaker type? It should be set to headphone.

I'll check the setting. As for the isolation transformer I found out some of the earlier airpanes had issues because of how they were wired, and neede to have them installed. hereis a part number of what I'm going to try.

PAC RCA Filter SNI-1/3.5

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I'll check the setting. As for the isolation transformer I found out some of the earlier airpanes had issues because of how they were wired, and neede to have them installed. hereis a part number of what I'm going to try.

PAC RCA Filter SNI-1/3.5

Additionally, make sure it is outputting mono.

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Ho Tom,

 

I just read this on another forum. Here is a copy and paste.

 

At least in my airplane, with my avionics, the headset instructions (i.e., from both the Faro and Pilot) are counterproductive and actually create White Noise! They are: turn both headset ear volumes to maximum, then set the Intercom volume to a lowest comfortable level (and set the Intercom squelch as with any squelch); then, if one person desires a slightly lower volume, turn the earpiece volumes down a little bit on that headset. Well, in my plane I can assure you this guarantees White Noise during radio transmissions. What I have to do instead–and what has so far (three more flights) stopped the white noise–is to turn all headset volumes to lowest (or nearly so) settings, then adjust Intercom volume to lowest-readable level (by both people) and set Intercom squelch as normally. That's it!"

Hey Guys: It turns out that when I reported the above, way back when, I was actually just putting a band-aid on a sore. Now, I have found the cause of the sore--and applied a soothing, healing solution! The solution came from perusing a number of threads over at VansAirForce of folks with exactly the same problem with their ICOM A200 radios.

Here's the 'fix' I employed, based on their discussion threads: Insert a 3/32" hex wrench into the right front of the radio and use it to loosen the radio in the tray, then, pull the radio out 3/4-way until the MIC and SIDETONE small foil covers are exposed. Remove the MIC foil cover, insert a small screw driver and reduce the mic gain by turning counterclockwise. I turned about a 1/2-turn first and it was way too far, eliminating my transmit (couldn't hear the "keying") and sidetone (i.e., ability to hear yourself talk). So I pulled the radio out again and dialed that mic setting back 1/2-way to start position.

Perfection! We tested it thoroughly on the ground and in the air. It is now the cleanest, clearest radio I have had in the 3.5 years I've owned the airplane. Why didn't somebody tell me this before so other aircraft and I didn't have to listen to all that white noise?

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Great post Roger.

Thank you for sharing.

 

The Van's site is another great source of information.

I came within a cat's whisker of buying a S-LSA RV-12, but settled on a CTSW instead. It was really what I wanted all along.

No buyers remorse here . . . glad I made that call. The SW is a great little airplane and fits my mission perfectly.

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Roger, I know someone who may be having this issue, so thanks for posting that.

 

As I posted earlier I found the problem to be related to the GPS. After a talk with PS Engineering and a search on the web I came up with this.

http://www.plane-power.com/Noise%20article.pdf

I am going to order the part and see if this will fix it. I do remember seeing something like this behind a panel on other CT's before.

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Betwwen it's small size and fragile connection scheme, the rotax cap should really be replaced with something like this Kemet

http://ctflier.com/index.php?/topic/1735-position-light-and-battery-upgrades-and-fixes/?hl=kemet

which Digikey carries. Goes a long way towards killing the noise even if you have a high impedance ground loop wired to the radio/intercom

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Hi Tom,

 

I'm surprised that that plane is having such an issue when many others are configured the same without any issues, unless this was an add on by an electronics shop after the plane came to the US.

I talked with Tom G about this, and he said many of the early airplanes had this issue. It has to do with the was they did the wiring. The later airplanes had the issue fixed.

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Did you get any specifics?

He said they used to go to Radio Shack and get a filter. Our Radio Shack is closing, because thay were making them buy all new inventory again. The link I posted earlier mentions the filter, and the guys from PS Engineering said there was PnP filter that I could buy. I will know for sure when I get the part and the owner brings the airplane back to install it.

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Seems like it would be less time to just rewire the radio and intercom than throw tons of hours at it and still have the problem. Sometimes starting from the beginning is a shorter route than starting in the middle.

Rewiring would be a big time consuming mess, and the problem would have likely still been there. My biggest problem with this and many other projects this winter has been being able to get things out and run them. Trying to find engine noise requires running the engine. When I started trying to track this down we had gust to 35, and 25 the next day. Anyway I learned something in trying to figure this out. While running the engine I started shutting off equipment at the circiut breakers until the noise went away. I was surprised when the noise went away when I shut off the GPS. I then turned it back on and unplugged the 3.5 audio plug from the back of the GPS and the noise was gone.

This is the sorce of the noise. This is when PS Engineering told me I needed an isolation filter in the line.

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He said they used to go to Radio Shack and get a filter. Our Radio Shack is closing, because thay were making them buy all new inventory again. The link I posted earlier mentions the filter, and the guys from PS Engineering said there was PnP filter that I could buy. I will know for sure when I get the part and the owner brings the airplane back to install it.

If it's a wiring problem, I would rather fix it than cover it up.

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  • 4 weeks later...

I didn't get a chance to run the airplane after I installed this "PAC RCA Filter SNI-1/3.5", but the owner says the headsets are quiet now. This isolated the ground loop from the GPS where the audio cable was tied to the 3.5mm aux jack on the instrument panel. This is wired in the aux input for the intercom. Cost was about $15 dollars from Amaxon and about 5 minutes to install.

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