nuckollsr(at)cox.net
Guest
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 Posted: Sat Jul 22, 2006 8:39 am Post subject: Strobe noise |
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At 03:00 PM 7/21/2006 -0400, you wrote:
| Quote: |
In a message dated 7/21/06 10:42:50 AM Eastern Daylight Time,
nuckollsr(at)cox.net writes:
<snip>
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| Quote: |
> In my whole career, I've never found it useful to add
> shielding or to reposition equipment or its wiring as
> a means for improving performance. If the original
> poster of the problem can describe the results of any
> experiments described in the 'Connection (or elsewhere)
> to identify the propagation mode, then remedies are
> readily at-hand to break that mode.
>
> Bob . . .
>
================================
Thank you Bob!
That is exactly what I said. As the saying goes you do not have to reinvent
the wheel.
Start with the basics and work from there. The original post by this fellow
contained information that he tried to obtain the Radio Shack noise filter
...
And I must say they surely do work. He did not have success getting it but
did obtain a second brand. He did not have any luck with that filter. What
should he do? Start with the basics and work from there.
I have found just the opposite from you ... I have done at least 4 planes
where repositioning the wires and/or running shielded wire have made a great
improvement, or totally eliminated the problem.
|
If the addition of shielding over-and-above that called
out by the instruction manual -OR- or repositioning of wires
mitigated the symptoms then I'll suggest there's a fundamental
flaw in either the devices involved or the manner in which they
are installed.
| Quote: | Other things I do after the
basics are Filters, Tolroid Cores, Feed Through Capacitors, Capacitors to
Ground
and Shorten wire leads. Sometimes one arrow does not kill the Sphinx. And I
still have not used all my arrows. One step at a time, starting with the
basics
as you said... Good installation practices.
I have always said ... YELLED about improving GROUNDS and connections. Ya
gots ta start somewhere ... Starts wit da basics.
|
Agreed. So let us DO start with the simple-ideas which guide
design and fabrication of products for aircraft (or any
other market). They are illustrated by a piece I published on
the website at:
http://aeroelectric.com/articles/Whats_all_this_DO160_Stuff_Anyhow.pdf
This piece speaks to a design philosophy that is well respected in
the aviation community and elsewhere. It suggests ways that we
can assure the neighborly function of any electro-whizzie in
a community of other electro-whizzies aboard aircraft. The goal
make the individual black box stand-alone-compatible when
installed per the designer's instructions.
When successfully applied, the installer is never required
to amplify the installation instructions with the
additions of shields, filters, repositioning of wires, or
agonizing over which end of which shield gets attached to what
locations.
If the devices involved were crafted with DO-160 philosophy
in mind, then problems with the installation are invariably caused
by some failure/deficiency of hardware or mistake in installation.
It's never expected that the customer should fine-tune
an installation with extra-ordinary noise mitigation studies
or techniques.
----------------------------------------------------------------
| Quote: | Actually I thought this issue was dead ... Well, at least the horse did not
move.
|
The "issue" is that a participant here on the List has
a problem. It's in the best interest of the List to guide
that individual through the identification and sifting
of the simple-ideas upon which the problem rests. To
accomplish this we need data:
What does the noise sound like, how does the interference
manifest itself? What positioning of controls or opening of
power/signal paths has an effect on the interference? Does
the problem go away or is it affected by operating the victim
or antagonist from a separate battery supply?
Assuming the hardware involved in this case has been successfully
installed in the past (Meaning that the manufacturer probably DOES
embraced and achieve DO-160 style neighborliness) then the
first task is to see where instructions were (1) not followed
or (2) unclear.
As this data becomes available, we should begin to zero
in more detailed tests that help us deduce root cause,
propagation mode. Ultimately we'll be able to suggest
techniques for eliminating the interference at the source
or at least breaking the propagation mode.
Until we do the science, dumping lots of suggestions
for remedy on the table are not particularly helpful
especially when remedies that do improve the situation
may only be masking the real cause.
I've never (well, almost never) found after-installation
application of shields, filters, etc. to be the ultimate
solution because the world I work in is supplied with
product that is expected and generally does work as-expected
when installed into environment considered during the design
of that product.
There have been a few instances of design-lag . . .
For example, I spent some time last winter ADDING filters
to the harness of starter-generator controllers on some VERY
expensive airplanes when moving wires and fiddling with shields
didn't help. Root cause was that the controllers were
designed in 1970 for a more benign environment and
not suited to the present day application. Folks in
production flight had pushed a few problem airplanes out
the door for years by tinkering with the installation. But
they finally encountered a set of conditions where the
alchemy didn't work. It was necessary and beneficial to
deduce root cause and enhance the design . . . even if
external to the victim. The fix is now a standard recipe
for success and I don't expect to get a call on that
problem ever again.
To go after a problem with the sprinkling of alchemy
is a tacit confession that we don't believe the products
involved were skillfully crafted to the task in the
first place. That MIGHT be true but I'll suggest that
it's better to deduce it based on understanding of
the simple-ideas than to sprinkle fixes until the problem
goes away or simply becomes tolerable.
Bob . . .
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