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eb
Joined: 06 Nov 2010
Posts: 1
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 Posted: Sat Nov 06, 2010 5:17 pm Post subject: instrument ground loops? |
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My radio, transponder and EFIS each have continuity between their respective ground wire and their external case--this is normal AFAIK. But each case is attached to an aluminum instrument panel, which is connected to a steel airframe. Can you say ground loops? (the instrument ground wires connect to a lug on the airframe). This creates 3 ground loops approximately 2' long each. Is this a problem--in terms of radio noise or interference?
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nuckolls.bob(at)aeroelect
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| Posted: Sat Nov 06, 2010 8:52 pm Post subject: instrument ground loops? |
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At 08:17 PM 11/6/2010, you wrote:
| Quote: |
My radio, transponder and EFIS each have continuity between their
respective ground wire and their external case--this is normal
AFAIK. But each case is attached to an aluminum instrument panel,
which is connected to a steel airframe. Can you say ground
loops? (the instrument ground wires connect to a lug on the
airframe). This creates 3 ground loops approximately 2' long
each. Is this a problem--in terms of radio noise or interference?
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Not if you don't hear any noise. Just because there ARE
multiple ground paths giving rise to potential coupling
of noise between antagonist and victim doesn't automatically
say it's going to happen . . . only that the risks are higher.
The drawings that configure a legacy TC aircraft's ground
wires many have been revised many times over the years
to deal with specific issues . . . and there may still
be potential issues.
The best action right now is to commend you for being
attentive to the risk which will give rise to
closer scrutiny when you start firing things up. Chances
are pretty good that you won't have any problems. If you
DO, then there are orderly ways to deduce "death by
Col. Mustard in the library with a knife".
Bob . . .
////
(o o)
===========o00o=(_)=o00o=========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
=================================
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fvalarm(at)rapidnet.net
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| Posted: Sat Nov 06, 2010 9:57 pm Post subject: instrument ground loops? |
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Bob,
Sort of related...
My LR3C voltage regulator has surprisingly large mounting holes. 5/16 IIRC.
Is this because there should be an isolation washer to prevent the bolts and
case from touching the metal mounting surface? I don't have any bolts with
such a large diameter and so short of grip length. I was considering
drilling for #8 screws in between the factory holes until I saw this thread.
Bevan
RV7A
--
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nuckolls.bob(at)aeroelect
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| Posted: Sun Nov 07, 2010 4:57 pm Post subject: instrument ground loops? |
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At 11:53 PM 11/6/2010, you wrote:
| Quote: |
Bob,
Sort of related...
My LR3C voltage regulator has surprisingly large mounting holes. 5/16 IIRC.
Is this because there should be an isolation washer to prevent the bolts and
case from touching the metal mounting surface? I don't have any bolts with
such a large diameter and so short of grip length. I was considering
drilling for #8 screws in between the factory holes until I saw this thread.
|
Good question . . .
The footprint for the LR series regulators was
cloned from a series of production regulators
and I don't even remember now who's devices . . .
They were commonly mounted on nut plates but with #8
hardware and flat washers. I don't know why they would
choose to do this other than to have a lot of tolerance
for hole locations on the mounting plate. You can drill
new holes or put washers under the heads of smaller screws.
In about 25 years and thousands of sold units, you're
the first I can recall that noticed and asked the
question. I think it was a Lamar footprint and we simply
cloned it with the idea of making it a drop-in replacement.
Bob . . .
////
(o o)
===========o00o=(_)=o00o=========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
=================================
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