Today's Message Index:
----------------------
1. 05:29 AM - Re: Electrical grounding block (Sam Marlow)
2. 06:17 AM - Re: Re: ELT Antenna Placement (Robert L. Nuckolls, III)
3. 06:30 AM - Re: Electrical grounding block (Robert L. Nuckolls, III)
4. 08:05 AM - Re: Grounding question (Robert L. Nuckolls, III)
5. 12:04 PM - Re: Re: ELT Antenna Placement (Craig Payne)
6. 01:40 PM - ELT Rubber Ducky Antenna? (bcondrey)
7. 03:44 PM - Re: ELT Rubber Ducky Antenna? (Robert L. Nuckolls, III)
8. 03:44 PM - Re: Electrical grounding block (LarryRobertHelming)
9. 04:05 PM - Re: ELT Rubber Ducky Antenna? (Craig Payne)
Message 1
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Subject: | Re: Electrical grounding block |
--> AeroElectric-List message posted by: Sam Marlow <sam.marlow@adelphia.net>
Thanks, good source!
Do not archive.
Bill Steer wrote:
>--> AeroElectric-List message posted by: "Bill Steer" <steerr@bellsouth.net>
>
>B&C. Take a look at www.bandcspecialty.com.
>
>Bill
>
>Do not archive
>
>
>
>
>>Anybody care to share whwer they purchased a grounding block?
>>
>>
>
>
>
>
>
>
>
>
>
Message 2
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Subject: | Re: ELT Antenna Placement |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 12:00 PM 5/26/2006 -0600, you wrote:
>--> AeroElectric-List message posted by: "Craig Payne"
><craig@craigandjean.com>
>
>The instructions for my new Artex ME406 406 MHz ELT have additional
>requirements:
>
>"Locate the antenna at least 30 inches away from other antennas, wires,
>vertical stabilizer, etc. to minimize distortion of the radiated field and
>interference with other equipment. The antenna must be installed VERTICALLY
>(within 15 of the vertical plane is acceptable). Artex has no performance
>data for installations that deviate from the stated requirements."
>
>(http://www.artex.net/documents/570-1600Rev-1.pdf)
>
>This is almost impossible on my Zenith 601XL so I am doing the best I can.
. . , which is all anyone can. Virtually every manufacturer cites
their fondest wishes in the installation manual that virtually
never work out in real life.
Generally, effects of 'deviations' require laboratory grade
instruments to detect and quantify . . . and most have no
major contribution to the outcome of any given crash/recovery
scenario.
Don't loose any sleep over it.
Bob . . .
---------------------------------------------------------
< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >
---------------------------------------------------------
Message 3
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Subject: | Re: Electrical grounding block |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 07:19 PM 5/26/2006 -0500, you wrote:
>--> AeroElectric-List message posted by: "LarryRobertHelming"
><lhelming@sigecom.net>
>
>I bought mine from B&C electric. I bought one of each size. A small one
>for the main buss, and large one for the ground, and the medium size for the
>e-buss. I had to double up a few on the ground buss cause I ran every
>ground back to the buss. Larry in Indiana
Don't understand how you used these for "the main buss" and
"e-bus" . . . I can't think of any rationale for having separate
grounds dictated by which power bus they're associated with . . .
Bob . . .
Message 4
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Subject: | Re: Grounding question |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 05:12 PM 5/26/2006 +0200, you wrote:
>--> AeroElectric-List message posted by: Mickey Coggins
><mick-matronics@rv8.ch>
>
> >> In my case in my RV Super 8 with my Batt in the back, I grounded it
> >> locally & ran a 12ga to the front, from the battery, for grounding of
> >> all the 'stuff' to a single point. I have a perfectly quiet electrical
> >> system. For all practical purposes, only the starter & alternator, are
> >> using the airframe ground.
> >> Mike
> >
> > Not a good deal. That long ground isn't really a ground. Please
> > consider using the single point ground block mounted on the firewall
> > as depicted in the Connection and making all cockpit and forward
> > accessory grounds at that point limiting your local airframe grounds
> > to the list cited in my posting of last night.
>
>I'm confused. Why wouldn't Mike's 12ga wire extended to an
>isolated forest of tabs be a ground?
>
>I considered doing the same, but decided to ground the
>forest of tabs to the front of the aircraft as well.
>
>Here's how mine is set up:
>
>http://www.rv8.ch/article.php?story=20060301215616213
>
>I added the "fat" ground wire between the front forest
>of tabs to the batteries in the back mainly to carry
>starter currents a bit more efficiently. I was afraid
>that if I didn't, something between where I ground
>the engine and the battery would get welded together
>when I cranked the starter.
>
>BTW, the engine cranks fine, but I have no idea about
>noise, since I don't yet have my radio installed.
"Ground" systems are much more than multiple systems
simply sharing a common conductor to satisfy their
individual needs for conductivity. The dynamic nature
of "ground" is dependent on its conductivity, geometry
and discontinuities. The ideal vehicular "ground" conductor
would probably be a welded joint, relatively thick sheet
of highly conductive material . . . say copper or silver
and have the minimum possible surface area to enclose
a given volume . . . hence a sphere.
Spheres and copper do not lend themselves well to
the fabrication of vehicular structures so instead
we find ourselves dealing with a variety of materials
ranging from excellent insulators (epoxy/glass) to
pretty good conductors (stir-welded aluminum) and all
technologies in between. Further, they're not spherical.
To make matters more interesting, the conduction pathways
for systems that share "ground" in any vehicle are never
straightest lines between two points on the system.
Just to make matters still more interesting, the
prudent designer has to consider the effectiveness
and cross coupling of signals for frequencies ranging
from DC to microwave. There's a condition in the
RAC Hawker 800 series aircraft where an antenna system
using airframe for part of the antenna's RF 'ground'
excites spaces in the hell-hole to the tune of over
100 volts/meter at various HF frequencies when the
transmitter is keyed. It varies from airplane to airplane
and is not a "problem" for most airplanes. But the effects
are present on every airplane and from time to time,
rise up and halt delivery of a multi-million dollar
machine because the ground system was not properly
configured for this application. Worse yet, it
would cost staggering amounts of money to fix it
now. Instead, we craft individual Band-Aids
on an airplane-by-airplane basis when a particular
combination of circumstances rise to intolerable
interference levels.
This dissonant array of conditions that never
approach the ideal ground system is NEVER a problem
for any one system operating by itself . . . nor is
it a problem for systems that are generally not vulnerable
to ground induced coupling of noises from a potential
antagonist to a potential victim system.
This gives rise to many builder's assertions that
their particular version of a ground system "works
just fine" . . . and he's not wrong. Just as I've cited
for the Hawkers above, there are ground system issues
that while they are predictable and even measurable,
the magnitude of the 'interference' is below the
threshold of deleterious effects. This is why
99.9% of all airplanes crafted over the last
100 years are considered by their owners to be
'satisfactory' performers. Only the occasional
machine comes to the attention of some poor
avionics tech who now has to figure out how to
work around a noise problem that would have best
been designed out in the first place.
Ladies and gentlemen, to offer a comprehensive
course in ground system design features and effects
of poor science is beyond the scope of activities
we can offer in this venue. You folks need to concentrate
on getting first-light-under-the-wheels with a minimum
of $time$ and lowest practical cost of ownership later.
Be wary of variations on a theme for ground system
features that depart from those suggested in the
'Connection and in the considered words of the
grey-beards on the List. Virtually every variation
offered to you by some builder you met at a fly-in
will be touted as a 'solution' to some unfounded
concern or a desire to cut a corner . . . and since
the airplane flew to that gathering, no doubt the
owner will report "it works fine". The grounding
philosophies offered in this venue are a prophylactic
effort designed to avoid that 0.1%, pain-in-the-arse
airplane that's going to be expensive in $time$
at some point in the future. These same philosophies
also attenuate the 10-20% of the airplanes that have
some degree of noise issue which the owner is willing
to accept as below his personal threshold of deleterious
performance.
The double-grounding architecture described above is
generally not a significant improvement in ground
system performance and opens the doors for new issues.
In another time, I'll tell you the saga of a "double
ground" issue that rose up in a Beechjet a year or
so ago that had a very expensive airplane down for
months (at taxpayer expense) and took hundreds of
hours to find and fix.
"Extending" ground busses for major chunks of system
hardware on the end of a 12AWG wire makes everything
'grounded' by that wire subject to single point failure
of one wire. Further, the resistance/inductance
contributed to the system by the wire length makes
it less than ideal ground.
These are 'experimental' airplanes and one can certainly
do as he/she wishes in terms of personalizing the
electrical system architecture. Most variations will
be found to function in a 'satisfactory' manner.
Just be aware that departures from architectures
configured with use of well considered science and experience
tosses out the $time$ invested in crafting those architectures.
They also elevate the risk for added expense and aggravation
at some later date. The fruits of those investments are being
shared with you at virtually zero expense so as to minimize
$time$ to first-light and $time$ needed to fix something later
when you'd rather be flying.
Bob . . .
Message 5
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Subject: | Re: ELT Antenna Placement |
--> AeroElectric-List message posted by: "Craig Payne" <craig@craigandjean.com>
>> Don't loose any sleep over it.
>>
>> Bob . . .
The other listed requirement is "do not crash" :-)
-- Craig
Message 6
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Subject: | ELT Rubber Ducky Antenna? |
--> AeroElectric-List message posted by: "bcondrey" <bob.condrey@baesystems.com>
Bob N.,
In the past you've cited the possibility using a rubber ducky style antenna for
ELTs. Would this also be an option for the newer style 121.5/406 MHz types such
as the Artex ME406?
Thanks
Bob
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=36874#36874
Message 7
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Subject: | Re: ELT Rubber Ducky Antenna? |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 01:35 PM 5/27/2006 -0700, you wrote:
>--> AeroElectric-List message posted by: "bcondrey"
><bob.condrey@baesystems.com>
>
>Bob N.,
>
>In the past you've cited the possibility using a rubber ducky style
>antenna for ELTs. Would this also be an option for the newer style
>121.5/406 MHz types such as the Artex ME406?
>
>Thanks
>Bob
Only if the "rubber duck" has been crafted for dual frequency
operations. The instance I suggested that the shortened antenna
be considered was the case where a pair of antennas . . . a 121.5
and a 406 MHz device were mounted side by side under the fiberglas
toe cover of the vertical fin fairing on a Beechjet:
http://www.aeroelectric.com/temp/400A_ELT.jpg
When the fairing cover was installed, metallic braces in
the fairing upset the SWR on the longer, 121.5 MHz antenna
and caused self-test failures. They considered the short antenna
until we discovered that the ELT had been qualified under TSO with
these specific antennas . . . we couldn't use a different
antenna without re-qualifying. So . . . they widened the
trip tolerance on the SWR self check . . . another case where
under very un-helpful regulation, two wrongs made a "right."
(sigh)
Anywho, I suspect your more modern design is paired with
an antenna designed for optimum performance at two frequencies
and the simple rubber duck is not an option for you.
Bob . . .
---------------------------------------------------------
< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >
---------------------------------------------------------
Message 8
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Subject: | Re: Electrical grounding block |
--> AeroElectric-List message posted by: "LarryRobertHelming" <lhelming@sigecom.net>
You have lost me somewhere Bob. I agree there is no need for separate
ground busses. Your book sold me on the need for separate power busses. I
was referring to all busses when I mentioned large, medium and small. The
busses -- which ever purpose they are placed into duty for -- are all sold
by B&C under the description of buss. There is no distinction of their use.
There are different sizes and the grounding buss, which serves all power
needs, requires the largest number of terminals. Thanks for calling this
need for clarification to my attention. Larry in Indiana
----- Original Message -----
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
> <nuckollsr@cox.net>
>
> At 07:19 PM 5/26/2006 -0500, you wrote:
>
>>--> AeroElectric-List message posted by: "LarryRobertHelming"
>><lhelming@sigecom.net>
>>
>>I bought mine from B&C electric. I bought one of each size. A small one
>>for the main buss, and large one for the ground, and the medium size for
>>the
>>e-buss. I had to double up a few on the ground buss cause I ran every
>>ground back to the buss. Larry in Indiana
>
>
> Don't understand how you used these for "the main buss" and
> "e-bus" . . . I can't think of any rationale for having separate
> grounds dictated by which power bus they're associated with . . .
>
>
> Bob . . .
>
>
>
Message 9
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Subject: | ELT Rubber Ducky Antenna? |
--> AeroElectric-List message posted by: "Craig Payne" <craig@craigandjean.com>
>>
Anywho, I suspect your more modern design is paired with
an antenna designed for optimum performance at two frequencies
and the simple rubber duck is not an option for you.
Bob . . .
<<
The Artex 121.5/406.028 MHz ELTs can be bought bundled with antennas
selected to support the dual frequencies. That's what I did. I'll tell you
how it works after my next crash.
-- Craig
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