Today's Message Index:
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1. 11:09 AM - Re: Troubleshooting radio whine/noise on C essna 182P (sacha)
2. 02:40 PM - Re: Re: Troubleshooting radio whine/noise on C essna 182P (Paul Millner)
3. 05:22 PM - Re: Re: Troubleshooting radio whine/noise on C essna 182P (Charlie England)
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| Subject: | Re: Troubleshooting radio whine/noise on C essna 182P |
I took some measurements of bus voltage using a Bluetooth oscilloscope called a
Mooshimeter. Here are 3 graphs. I'm also including a fourth one which is picture
of the voltage in my car cigar lighter for comparison.
Two things are noticeable:
1. The amplitude of the ripple in the aircraft is smaller by a factor of 3 or 4.
2. There seem to be higher frequency components in the aircraft than in the car.
Does anyone have any thoughts about this?
I'm thinking that maybe the noise suppression capacitor is fried and I'd like to
test this hypothesis without shelling out $125 for the Cessna part. Can anyone
suggest a sensible capacitor I could try out?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=450728#450728
Attachments:
http://forums.matronics.com//files/image_147.png
http://forums.matronics.com//files/image_348.png
http://forums.matronics.com//files/image_806.png
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Message 2
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| Subject: | Re: Troubleshooting radio whine/noise on C essna |
182P
There's a company in Texas that makes an aftermarket part... Aircraft
Spruce used to carry them.
Paul
On 12/2/2015 11:06 AM, sacha wrote:
>
> I took some measurements of bus voltage using a Bluetooth oscilloscope called
a Mooshimeter. Here are 3 graphs. I'm also including a fourth one which is picture
of the voltage in my car cigar lighter for comparison.
>
> Two things are noticeable:
> 1. The amplitude of the ripple in the aircraft is smaller by a factor of 3 or
4.
> 2. There seem to be higher frequency components in the aircraft than in the car.
>
> Does anyone have any thoughts about this?
> I'm thinking that maybe the noise suppression capacitor is fried and I'd like
to test this hypothesis without shelling out $125 for the Cessna part. Can anyone
suggest a sensible capacitor I could try out?
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=450728#450728
>
>
> Attachments:
>
> http://forums.matronics.com//files/image_147.png
> http://forums.matronics.com//files/image_348.png
> http://forums.matronics.com//files/image_806.png
> http://forums.matronics.com//files/image_413.png
>
>
Message 3
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| Subject: | Re: Troubleshooting radio whine/noise on C essna |
182P
On 12/2/2015 1:06 PM, sacha wrote:
>
> I took some measurements of bus voltage using a Bluetooth oscilloscope called
a Mooshimeter. Here are 3 graphs. I'm also including a fourth one which is picture
of the voltage in my car cigar lighter for comparison.
>
> Two things are noticeable:
> 1. The amplitude of the ripple in the aircraft is smaller by a factor of 3 or
4.
> 2. There seem to be higher frequency components in the aircraft than in the car.
>
> Does anyone have any thoughts about this?
> I'm thinking that maybe the noise suppression capacitor is fried and I'd like
to test this hypothesis without shelling out $125 for the Cessna part. Can anyone
suggest a sensible capacitor I could try out?
>
>
Is the Cessna device a simple capacitor? (If so, it'd have one lead
connected to the B lead and the other lead connected to ground.) A
simple capacitor could be purchased at any well stocked electronic
supply; just ask for, for instance, a 2000 mfd 50 volt electrolytic
capacitor.
If it's an inductor, it will have 2 leads and be *in series* with the B
lead (one terminal toward the B terminal of the alt; the other terminal
toward the master contactor/buss). You could check ebay, Amazon, or your
local parts store for 'alternator noise filter' & find one that's
intended for hookup like I described.
A third type actually includes both an inductor and a capacitor. It
would have 3 leads: 1 to the alt B terminal, 1 toward the master
contactor/buss, and the last one to ground. Again, same search & pick
the device you need.
Note that most of the combination inductor/capacitor filters intended
for automotive use will have limited current carrying capacity because
they're intended for insertion in line with a single load; not in the B
lead, where they must carry the entire load of the generating system.
For testing purposes, just leave all the really big electrical loads off
(landing lights, etc) and make sure the battery is charged up prior to
the test. The light-duty stuff I saw was in the $5-$25 range.
You can see images & diagrams by googling 'alternator noise filter' &
picking google's images display.
BTW, a 3 terminal whole-a/c filter for $125 might not be that bad if
that's what is broken.
http://www.amazon.com/NewMar-150--150-Noise-Filter/dp/B008P0UPD4/ref=sr_1_2?s=car&ie=UTF8&qid=1449104711&sr=1-2&keywords=alternator+noise+filter
Charlie
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