Today's Message Index:
----------------------
1. 04:10 AM - Re: Antenna Ground Planes (Alec Myers)
2. 05:42 AM - don't count on control wire to turn IR alternator off (johnbright)
3. 05:53 AM - Re: OV relay and crowbar (johnbright)
4. 09:04 AM - Re: Antenna Ground Planes (AdventureD)
5. 09:47 AM - Re: Re: Antenna Ground Planes (Charlie England)
6. 10:11 AM - Re: Antenna Ground Planes (Robert L. Nuckolls, III)
7. 11:04 AM - Re: Alternator Ground (rparigoris)
8. 11:14 AM - Re: Antenna Ground Planes (user9253)
9. 05:10 PM - Re: Antenna Ground Planes (AdventureD)
10. 06:43 PM - Re: Antenna Ground Planes (user9253)
11. 07:33 PM - Re: Alternator Ground (rparigoris)
Message 1
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| Subject: | Re: Antenna Ground Planes |
A ground plane works the same way as a mirror: the boundary condition for th
e electric field at the surface of an infinite (or ground connected) ground p
lane is that no electric field component can exist parallel to the surface o
f the ground plane. To enforce this electric currents are induced in the gro
und plane to produce a cancelling field - equivalent to a reflected antenna m
irrored in the plane. If the ground plane is small or not connected to the t
ransmitter circuit then those currents are impeded to a greater or lesser ex
tent.
The effectiveness of a ground plane is improved if it is electrically connec
ted to the circuit that=99s connected to the antenna so those currents
flow more easily. But it will still have some effect even if it=99s n
ot.
The higher the frequency the more effective a floating ground plane will be:
at light frequencies a smooth metal surface is an almost perfect ground pla
ne (mirror) even when not electrically connected to anything else.
Bob - how did I do?
On Jan 16, 2021, at 02:35, Bob Verwey <bob.verwey@gmail.com> wrote:
=EF=BB
Dan there are no dumb questions...even though i dont know the answer to your
question...lol
On Sat, 16 Jan 2021, 06:05 AdventureD, <dobrien@microfoundations.com> wrote:
tions.com>
>
> Here is a dumb question about ground planes. Does the ground plane serve t
o direct the signal to the antenna irrespective of whether the antenna is "c
onnected" to the ground plane, or must the antenna itself be electrically co
nnected to the ground plane?
>
> I am asking because the tech says the best approach to the ground plane in
my e-glass composite is conductive paint on the belly. what I am wondering
is how, after the conductive paint is painted over, one ensures that the an
tenna is "grounded" to the conductive paint ground plane. I think it may be
the case that the ground plane has nothing to do with "grounding" the anten
na to the ground plane, but rather that the purpose of the ground plane is t
o absorb signal for the antenna located in the middle of it (whether or not t
he antenna "touches" the ground plane.
>
> As you can see, I obviously don't know how antenna ground planes work.
>
> Appreciate your help,
> Dan
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=500260#500260
>
>
>
>
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Message 2
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| Subject: | don't count on control wire to turn IR alternator off |
I don't know about all internally regulated alternators but it is common for the
control wire to turn the alternator on but have no ability to turn it off.
In any case, as stated in AeroElectric Connection book: The 'control input to the
alternator has no direct ability to open the field supply circuit and halt
a runaway condition.
Ref attached image snip from AeroElectric Connection book.
--------
John Bright, RV-6A, at FWF, O-360
Z-101 single batt dual alt SDS EM-5-F.
john_s_bright@yahoo.com, Newport News, Va
https://drive.google.com/drive/folders/1u6GeZo6pmBWsKykLNVQMvu4o1VEVyP4K
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=500266#500266
Attachments:
http://forums.matronics.com//files/aec_r12ac1_page_3_3_153.jpg
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| Subject: | Re: OV relay and crowbar |
I don't know about all internally regulated alternators but it is common for the
control wire to turn the alternator on but have no ability to turn it off.
In any case, as stated in AeroElectric Connection book: The 'control input to the
alternator has no direct ability to open the field supply circuit and halt
a runaway condition.
Ref attached image snip from AeroElectric Connection book.
--------
John Bright, RV-6A, at FWF, O-360
Z-101 single batt dual alt SDS EM-5-F.
john_s_bright@yahoo.com, Newport News, Va
https://drive.google.com/drive/folders/1u6GeZo6pmBWsKykLNVQMvu4o1VEVyP4K
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=500267#500267
Attachments:
http://forums.matronics.com//files/aec_r12ac1_page_3_3_193.jpg
Message 4
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| Subject: | Re: Antenna Ground Planes |
I think youre saying that around an antenna will work to some degree even if it
is not electrically connected to the antenna. If that is true, conductive paint
will work to some degree even if sealed over by actual paint. To make it
even better, should the inside of the hole drilled to accept the antenna be coated
with the conductive paint so there is a connection between the ground plane
and the antenna. From what you are saying, it appears that that would make
the ground plane work even better.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=500268#500268
Message 5
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| Subject: | Re: Antenna Ground Planes |
On Sat, Jan 16, 2021 at 11:10 AM AdventureD <dobrien@microfoundations.com>
wrote:
> dobrien@microfoundations.com>
>
> I think you=99re saying that around an antenna will work to some de
gree even
> if it is not electrically connected to the antenna. If that is true,
> conductive paint will work to some degree even if sealed over by actual
> paint. To make it even better, should the inside of the hole drilled to
> accept the antenna be coated with the conductive paint so there is a
> connection between the ground plane and the antenna. From what you are
> saying, it appears that that would make the ground plane work even better
.
>
> Even on a composite airframe, you'll likely need some form of doubler to
spread the mechanical loads out from the mount. Why not just use properly
dimensioned aluminum sheet inside the fuselage? Weight gain of an ounce or
three, and guaranteed ground plane in addition to the doubler function.
If the plane is 'glass (not carbon), the best idea was already offered: put
the entire assy inside the fuselage.
Charlie
Message 6
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| Subject: | Re: Antenna Ground Planes |
At 06:06 AM 1/16/2021, you wrote:
<snip>
If the ground plane is small or not connected to the transmitter
circuit then those currents are impeded to a greater or lesser extent.
<snip>
The higher the frequency the more effective a floating ground plane
will be: at light frequencies a smooth metal surface is an almost
perfect ground plane (mirror) even when not electrically connected to
anything else.
Bob - how did I do?
Very good!
At a hammer-n-tongs level I like to envision
ground planes from two perspectives. The common
terrestrial version utilizes what I would
call a 'resonant' ground plane.
The goal of a ground plane is to
provide a minimal loss (lowest practical
metallic resistance) non-radiating
conductor to concentrate radiation
energy in the vertical element.
Consider a vertical dipole antenna with
a feedline attached to the center. You
have two elements in the same plane
that share energy management tasks for
emitting and receiving energy.
Now, fold the bottom element 90 degrees
to horizontal. Intuitively, one can see
that this element is now in vigorous argument
with the vertical element for squirting
energy off into the ether.
Each element has a load impedance on the order
of 30 ohms. Suppose we added a second horizontal
element opposite the first. Now we have TWO
radiating elements with a combined load impedance
of 15 ohms . . . now we can calculate that
energy fed to the base will have a 15:30 division
ratio with most of energy going to the 'good
guy'.
Okay, let's add two more radials elements disposed
90 degrees from the first two. Now we have a
load impedance of 30/4 or 7.5 ohms for the
combination of bad guys . . . and 80% of the
energy at the end of the feedline goes to the
'good guy'. 4-radials is a practical place to
stop adding . . . the difference between 80
and 100% of energy going to the 'good guy' is
not observable in practice.
But we don't need to stop there. If you droop
the radials at about 45 degrees, you increase
the theoretical feed point impedance of 30
ohms (close but not quite 1:1 swr for 50
ohm feedline) the match is a bit better and
one of several potential losses in the system
is reduced. Drooping also reduces the radiation
angle of the antenna so as to focus more attention
at the horizon as opposed to the Andromeda
galaxy.
On the other hand, you can add an infinite number
of radials forming a solid disk. Now the theoretical
load impedance of the plane approaches zero
ohms . . . a good thing you can do to improve
performance.
Now, here comes those pesky machines known as
airplanes . . . with envelopes and structures
that are not very friendly for seeking an
optimal antenna installation.
In a plastic airplane, you can choose to go the
enhanced or optimized route for achieving a
suitable ground plane. At ADSB/XPNDR frequencies
the optimized route is pretty easy. The disk
is relatively small. At VHF frequencies, the disk
is unmanageably larger so optimization with
4 or more 'radials' becomes the technique of
choice.
The short answer is that mounting antennas
on the outside of a metal airplane offers
a perfectly satisfactory ground plane although
the infinite number of radials are not resonant.
No big deal. In a plastic airplane, the ground
plane needs to be fabricated and going the
resonant mode with either a disk (optimal)
or radials (enhanced) works good, last a long time.
The native conductive qualities of materials
in composite airplanes whether carbon-fiber,
paint or any spray on coatings don't even
begin to approach the much-desired quest
for close-to-zero-ohms qualities of the
optimized ground plane.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 7
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| Subject: | Re: Alternator Ground |
Hi AdventureD "if the alternator is already grounded via attachment to the case,
why would that be needed?" See my post on this thread about the V tail bonanza
alternator. I located a bad connection between the two halves of the alternator.
Running a separate wire to ensure the back hald of the alternator isn't
a bad idea if you didn't want to disassemble alternator. Ron P.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=500272#500272
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| Subject: | Re: Antenna Ground Planes |
> I think youre saying that around an antenna will work to some degree even if
it is not electrically connected to the antenna. If that is true, conductive paint
will work to some degree even if sealed over by actual paint. To make it
even better, should the inside of the hole drilled to accept the antenna be coated
with the conductive paint so there is a connection between the ground plane
and the antenna. From what you are saying, it appears that that would make
the ground plane work even better.
Nobody above said that conductive paint will work as an antenna ground plane
except the OP's misinformed tech. Yes, conductive paint does have some conductive
properties.
It also has high resistance, too high to make an effective ground plane.
After installing the com antenna, check its SWR with a meter.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=500273#500273
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| Subject: | Re: Antenna Ground Planes |
> Nobody above said that conductive paint will work as an antenna ground plane
except the OP's misinformed tech. Yes, conductive paint does have some conductive
properties. It also has high resistance, too high to make an effective ground
plane. After installing the com antenna, check its SWR with a meter.
Funny thing is a bunch of Lancair guys believe (and say they have experienced)
that conductive paint works.
Let's suppose it doesn't work. Does the existence of the conductive paint over
e-glass do any harm when the antenna is put on the outside of the plane? If
one put 4 or 6 or 8 copper strips radiating out from the coax attach point on
the inside of the eglass plane, that would still work as well as if the conductive
paint weren't there, would it not? On the other hand, if I wanted to put
a strikefinder antenna on the bottom of the inside of the fuselage, I assume that
conductive paint could interfere with the signal to the strikefinder antenna
on the inside of the plane, yes? In that sense, would the conductive paint
actually do harm? [/quote]
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=500278#500278
Message 10
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| Subject: | Re: Antenna Ground Planes |
An antenna will work without a ground plane. But how well? The opinion of others
is subjective.
The best way to know how well an antenna works is with a SWR meter.
Conductive paint will not do any harm at all to the performance of an exterior
antenna.
It will not do much good either. Use whatever paint looks good.
Use a ground plane consisting of 4 wires or copper strips inside of the fuselage.
I am not knowledgeable about a strikefinder.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=500279#500279
Message 11
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| Subject: | Re: Alternator Ground |
Hi AdventureD For SD20 connector: https://bandc.com/product/replacement-field-connector-for-alternators-l-40-bc410-h-bc425-1-sk35-lom30/
as far as field wires,
they are to be paralleled to regulator. I have a SD20S and just twisted 2 wires
together from regulator to go to both field wires. One is not a ground. You
can just make a short paralleled wire as well. Here's install manual: https://bandc.com/wp-content/uploads/2018/05/install-instructions-bc410_revC.pdf
As
far as grounding for SD20, it's grounded by the 4 mounting nuts. I'm going the
belt and suspenders route and running an extra ground from one of the screws
on the brush side of case to engine ground. Note they want you to cross tighten
to 20 inch lbs, then go to 60 to 70 inch lbs. I'm going to weld up a 12 point
torque adapter for my 1/4" torque wrench. Manual tells you torque value for
B+ nut. Best not tighten to the old stand by of stripping and backing off 1/2
turn! Ron P.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=500280#500280
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