Today's Message Index:
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1. 06:10 AM - Re: Re: Radio Buzz (Robert L. Nuckolls, III)
2. 06:13 AM - Re: Radio Buzz (Robert L. Nuckolls, III)
3. 06:14 AM - Re: Re: Radio Buzz (Robert L. Nuckolls, III)
4. 09:15 AM - Re: Radio Buzz (Ross Home)
5. 11:46 AM - Re: Radio Buzz (rayj)
6. 12:26 PM - Re: Radio Buzz (Robert L. Nuckolls, III)
Message 1
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At 05:06 PM 7/19/2015, you wrote:
>
>Is the AFS 5600 EFIS wired according to the installation
>manual? Usually shielded cables are grounded at the source end
>only, but not always. Can you identify one or more wires from the
>AFS 5600 EFIS that are causing the noise?
> Is the squelch on the com radio adjusted too sensitive?
As a general rule, no appliance slated to use
in airplanes should require ANY special attention
on the part of the installer to mitigate a noise
issue. The qualification testing for TC aircraft
puts your black box out on a copper-top table, wires
it up to function stand-alone with no less than 2 meters
of "ship's wiring" and it should be neither sensitive
to or an emitter of unfriendly energy sources.
If any manufacturer suggests 'adding filters, moving
wires, adjusting antenna locations, etc. . . they
are admitting to their lack of due diligence in
design/fabrication of their product.
Bob . . .
Message 2
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At 06:16 PM 7/19/2015, you wrote:
>I will try to rig a short antenna. As it is, I get about 6-9 inches
>from the EFIS to set off the sniffer (a handheld radio)
>
>Ross Mickey
Your zeroing in on the root cause . . . I have
an h-t antenna that's only about an inch long with
a 1/2" disk soldered to the end. This can be used
to probe wires, openings in enclosures, lcd screens,
etc.
Of course, this only works with noise sources that have
strong amplitude modulated components . . . but if you
can 'hear' it in your nav-comm, you can generally 'sniff
it' with a hand-held.
Bob . . .
Message 3
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At 08:00 PM 7/19/2015, you wrote:
>
>If I dim my Dynon D-180 screen, it makes noise in the headset. I
>leave the screen on full bright (never fly at night) and the noise
>is not noticeable.
>Joe
Unfortunately, all too common . . .
Bob . . .
Message 4
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With my dumbed down handheld sniffer I have identified the major culprit and
perhaps a second. The main interference (80%-90%) is from an 18" piece of
unused OAT wire that is plugged into the main harness with pos, signal and
shield all pinned in the harness. In talking with AFS tech support, the
three options are, 1) connect the pos and signal wires together 2) connect
the signal and shield together or 3) unpin all three wires from the harness
and remove the whole thing.
The second culprit is a couple of the serial port wires (2 of the 4). These
are emanating some interference which is probably caused by my error. I
connected a black the wire coming out of the premade harness (which is
connected to the four shield wires for the serial ports) to ground rather
than to the chassis of the EFIS. The new harnesses from AFS (mine is two
years old) do not have this but take care of connecting the serial shields
to the chassis in the pinning of the harness.
I will check these out on Weds when I get back to the hangar.
Thank you all for your help.
Ross
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: Monday, July 20, 2015 6:12 AM
Subject: Re: AeroElectric-List: Radio Buzz
At 06:16 PM 7/19/2015, you wrote:
I will try to rig a short antenna. As it is, I get about 6-9 inches from the
EFIS to set off the sniffer (a handheld radio)
Ross Mickey
Your zeroing in on the root cause . . . I have
an h-t antenna that's only about an inch long with
a 1/2" disk soldered to the end. This can be used
to probe wires, openings in enclosures, lcd screens,
etc.
Of course, this only works with noise sources that have
strong amplitude modulated components . . . but if you
can 'hear' it in your nav-comm, you can generally 'sniff
it' with a hand-held.
Bob . . .
http://www.matronics.com/Navigator?AeroElectric-List
http://www.matronics.com/contribution
Message 5
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Does the disk make the the "detector" directionally sensitive, like I'm
guessing a loop would?
Raymond Julian
Kettle River, MN
The things we admire in men, kindness and generosity, openness, honesty,
understanding and feeling are the concomitants of failure in our system.
And those traits we detest, sharpness, greed, acquisitiveness, meanness,
egotism and self-interest are the traits of success. And while men
admire the quality of the first they love the produce of the second.
-John Steinbeck, novelist, Nobel laureate (1902-1968)
On 07/20/2015 08:12 AM, Robert L. Nuckolls, III wrote:
> At 06:16 PM 7/19/2015, you wrote:
>> I will try to rig a short antenna. As it is, I get about 6-9 inches
>> from the EFIS to set off the sniffer (a handheld radio)
>>
>> Ross Mickey
>
> Your zeroing in on the root cause . . . I have
> an h-t antenna that's only about an inch long with
> a 1/2" disk soldered to the end. This can be used
> to probe wires, openings in enclosures, lcd screens,
> etc.
>
> Of course, this only works with noise sources that have
> strong amplitude modulated components . . . but if you
> can 'hear' it in your nav-comm, you can generally 'sniff
> it' with a hand-held.
>
>
> Bob . . .
>
> *
>
>
> *
>
Message 6
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At 11:14 AM 7/20/2015, you wrote:
With my dumbed down handheld sniffer I have identified the major
culprit and perhaps a second. The main interference (80%-90%) is
from an 18" piece of unused OAT wire that is plugged into the main
harness with pos, signal and shield all pinned in the harness. In
talking with AFS tech support, the three options are, 1) connect the
pos and signal wires together 2) connect the signal and shield
together or 3) unpin all three wires from the harness and remove the
whole thing.
I would vote for removing any unused wires
from the connector.
The second culprit is a couple of the serial port wires (2 of the
4). These are emanating some interference which is probably caused
by my error. I connected a black the wire coming out of the premade
harness (which is connected to the four shield wires for the serial
ports) to ground rather than to the chassis of the EFIS. The new
harnesses from AFS (mine is two years old) do not have this but take
care of connecting the serial shields to the chassis in the pinning
of the harness.
Hmmmm . . . there's no good reason for serial
wires to radiate. Single wire data at the
higher speeds (20-100 kBits/sec) were subject
to some electro-static coupling issues but
the designers of RS232 transmitters offered
connections for a capacitor to slow the transition
edges of the data. Twisted pair data architectures
eliminated this risk.
I'm disappointed that the EFIS designers didn't
do a better job of managing this but yes, at
VHF, the long pig-tail on the shield ground could
add enough impedance to allow those pesky edges
to couple out. This may well be an instance where
the long pigtail not only added the series impedance,
it became the VHF friendly radiator for the noise.
I will check these out on Weds when I get back to the hangar.
Let us know what you discover . . . be sure to
let the supplier know too . . . they MIGHT see
fit to fix this at the next upgrade opportunity.
Bob . . .
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