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nuckolls.bob(at)aeroelect
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 Posted: Sat Jun 16, 2018 7:46 am Post subject: Paint question |
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Are there any Listers who can give me brands
and perhaps part numbers for non-metal airplane
paints understood to contain metallic fillers
of any kind?
Bob . . .
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email(at)jaredyates.com
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| Posted: Sat Jun 16, 2018 8:01 am Post subject: Paint question |
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Do you mean like Polyfiber's Polyspray?
On June 16, 2018 11:52:26 "Robert L. Nuckolls, III"
<nuckolls.bob(at)aeroelectric.com> wrote:
| Quote: |
<nuckolls.bob(at)aeroelectric.com>
Are there any Listers who can give me brands
and perhaps part numbers for non-metal airplane
paints understood to contain metallic fillers
of any kind?
Bob . . .
|
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nuckolls.bob(at)aeroelect
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| Posted: Sat Jun 16, 2018 8:48 am Post subject: Paint question |
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At 11:00 AM 6/16/2018, you wrote:
| Quote: | --> AeroElectric-List message posted by: Jared Yates <email(at)jaredyates.com>
Do you mean like Polyfiber's Polyspray? |
You tell me . . . finishes specific to airplanes
are not my field of expertise. I've read/heard
various assertions over the years concerning
the adverse effects of Paint X vs. Paint Y
on the performance of antennas mounting inside
the skin of a non-metal airplane. But I've
never had occasion to explore the facts and
physics of those assertions.
Just curious as to the most egregious of
supposed offenders . . .
Bob . . .
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peter(at)sportingaero.com
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| Posted: Sat Jun 16, 2018 8:51 am Post subject: Paint question |
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Bob,
Diamond aircraft specify an 'Anti-Static' primer to be applied to their
aircraft, however the outer layers of cloth also include an aluminium mesh
woven into the carbon.
One such primer is,
http://www.ppgaerospace.com/Products/Coatings-Removers-Cleaners/Commercial-C
ivil-Aviation/Specialty-Products/5421-2921-Anti-Static-Kit-TYPE-I.aspx
Not sure if this is has a metallic filler ... I can look on Monday what
paints are specified in the manual.
Peter
--
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peter(at)sportingaero.com
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| Posted: Sat Jun 16, 2018 8:52 am Post subject: Paint question |
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Bob,
Diamond aircraft specify an 'Anti-Static' primer to be applied to their
aircraft, however the outer layers of cloth also include an aluminium mesh
woven into the carbon.
One such primer is,
http://www.ppgaerospace.com/Products/Coatings-Removers-Cleaners/Commercial-C
ivil-Aviation/Specialty-Products/5421-2921-Anti-Static-Kit-TYPE-I.aspx
Not sure if this is has a metallic filler ... I can look on Monday what
paints are specified in the manual.
Peter
--
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kenryan
Joined: 20 Oct 2009
Posts: 426
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| Posted: Sat Jun 16, 2018 8:58 am Post subject: Paint question |
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I was told not to mount any antennas inside my silver Oratex SuperSTOL because the silver pigment contains metal that would block signals. I can send you some scraps if you would like to test it. Ken Ryan
Sent from my Android. Sorry Steve.
On Sat, Jun 16, 2018, 08:52 Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | At 11:00 AM 6/16/2018, you wrote:
| Quote: | --> AeroElectric-List message posted by: Jared Yates <email(at)jaredyates.com (email(at)jaredyates.com)>
Do you mean like Polyfiber's Polyspray? |
 You tell me . . . finishes specific to airplanes
 are not my field of expertise. I've read/heard
 various assertions over the years concerning
 the adverse effects of Paint X vs. Paint Y
 on the performance of antennas mounting inside
 the skin of a non-metal airplane. But I've
 never had occasion to explore the facts and
 physics of those assertions.
 Just curious as to the most egregious of
 supposed offenders . . .
 Bob . . .
|
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email(at)jaredyates.com
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| Posted: Sat Jun 16, 2018 9:07 am Post subject: Paint question |
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The official description: A high-solids aluminum-pigmented, 1 part, air drying resin used after the Poly-Brush preliminary coating to protect the fabric from UV and prepare for a smooth finish
Polyspray has aluminum particles but I don't know about how it blocks or does not block RF.
On June 16, 2018 12:54:44 "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com> wrote: | Quote: | At 11:00 AM 6/16/2018, you wrote:
| Quote: | --> AeroElectric-List message posted by: Jared Yates <email(at)jaredyates.com>
Do you mean like Polyfiber's Polyspray? |
You tell me . . . finishes specific to airplanes
are not my field of expertise. I've read/heard
various assertions over the years concerning
the adverse effects of Paint X vs. Paint Y
on the performance of antennas mounting inside
the skin of a non-metal airplane. But I've
never had occasion to explore the facts and
physics of those assertions.
Just curious as to the most egregious of
supposed offenders . . .
Bob . . . |
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ceengland7(at)gmail.com
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| Posted: Sat Jun 16, 2018 9:34 am Post subject: Paint question |
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On 6/16/2018 11:47 AM, Robert L. Nuckolls, III wrote:
| Quote: | At 11:00 AM 6/16/2018, you wrote:
| Quote: | --> AeroElectric-List message posted by: Jared Yates <email(at)jaredyates.com> (email(at)jaredyates.com)
Do you mean like Polyfiber's Polyspray? |
You tell me . . . finishes specific to airplanes
are not my field of expertise. I've read/heard
various assertions over the years concerning
the adverse effects of Paint X vs. Paint Y
on the performance of antennas mounting inside
the skin of a non-metal airplane. But I've
never had occasion to explore the facts and
physics of those assertions.
Just curious as to the most egregious of
supposed offenders . . .
Bob . . . |
I hate paint, and I'm certainly no expert. But I'd bet that the only paints that contain enough metal to be an RF issue would be the 'silver' step of fabric coatings, some of which (likely all the old stuff) contain aluminum dust as a UV blocker, and paints specifically sold as metallic and/or metalflake colors.
 Virus-free. www.avast.com [url=#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2] [/url]
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nuckolls.bob(at)aeroelect
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| Posted: Tue Jun 19, 2018 10:03 am Post subject: Paint question |
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| Quote: | | I hate paint, and I'm certainly no expert. But I'd bet that the only paints that contain enough metal to be an RF issue would be the 'silver' step of fabric coatings, some of which (likely all the old stuff) contain aluminum dust as a UV blocker, and paints specifically sold as metallic and/or metalflake colors. |
I am skeptical of the claimed effects for metallic
particles in the paint. Intuitively, one can easily
accept that placing conductive/refractive materials
in the path of an electromagnetic wave will have
some 'effect' . . . but to what degree?
In electromagnetic compatibility schools we're taught
that 'breaks in shields should be kept to 1/10th
wavelength at frequency of interest to avoid degrading
that shield's effectiveness'.
We've seen reflectors for centimeter wave, dish
antennas made from metallic mesh with significant
openings . . . yet so small compared to the wavelength
of the operating frequency as to behave as a solid
surface.
When you place a conductor (like a dipole antenna)
out in the air and exposed it to some EM field,
then energy at the frequency where the antenna is
resonant will excite the antenna and manifest with
a strong current node in the middle and voltage nodes
at the ends.
Now, you've got the 1/2 wave piece of wire 'singing'
in harmony with the constellations of energy that
are harmonic multiples of the resonant frequency.
What happens to that energy? If you've got a feeding
attached at the current node, you can suck of a substantial
part of that energy and route it someplace else . . . like
your VOR receiver.
But unless there is a feed line, energy exciting
the antenna will be rejected as heat from ohmic
losses at the current node or re-radiated. After
all, it HAS to go somewhere.
So what about those little bits of metal suspended in
an otherwise non-conductive paint? I suspect that a
really 'chunky' filling (0.001") flakes would be
the largest practical filler. What portion of a wavelength
is 0.001" compared to the wavelength of the comm
transceiver or even GPS?
Pretty small. This suggests that the currents induced
in such particles at our frequencies of interest are
vanishingly small, i.e. insignificant. These particles
ARE significant at wavelengths of light, hence effective
modifiers for those electromagnetic fields. However,
I suspect that there are no measurable effects for such
particles at our frequencies of interest.
Particle sizes are simply too far removed from resonance where
significant currents would be induced. No current,
no heat, no re-radiation, no measurable effects.
It's an easy experiment to conduct and I have the equipment
to do it . . . just no time at the moment and I'll need
to acquire some exemplar coatings to test.
If anyone is aware of quantified studies conducted on
this topic, I'd be grateful for some linkage. Anyone
conversant in an alternative explanation is encouraged
to correct my mis-conception . . .
Bob . . .
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echristley(at)att.net
Guest
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| Posted: Tue Jun 19, 2018 10:57 am Post subject: Paint question |
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If I'm not mistaken, Jim Weir did these experiments and documented them in his antennae booklet. I may be wrong, since it was years ago that I went through them, but I'm pretty sure that he even included a diagram.
On Tuesday, June 19, 2018 2:05 PM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com> wrote:
| Quote: | | I hate paint, and I'm certainly no expert. But I'd bet that the only paints that contain enough metal to be an RF issue would be the 'silver' step of fabric coatings, some of which (likely all the old stuff) contain aluminum dust as a UV blocker, and paints specifically sold as metallic and/or metalflake colors. |
I am skeptical of the claimed effects for metallic
particles in the paint. Intuitively, one can easily
accept that placing conductive/refractive materials
in the path of an electromagnetic wave will have
some 'effect' . . . but to what degree?
In electromagnetic compatibility schools we're taught
that 'breaks in shields should be kept to 1/10th
wavelength at frequency of interest to avoid degrading
that shield's effectiveness'.
We've seen reflectors for centimeter wave, dish
antennas made from metallic mesh with significant
openings . . . yet so small compared to the wavelength
of the operating frequency as to behave as a solid
surface.
When you place a conductor (like a dipole antenna)
out in the air and exposed it to some EM field,
then energy at the frequency where the antenna is
resonant will excite the antenna and manifest with
a strong current node in the middle and voltage nodes
at the ends.
Now, you've got the 1/2 wave piece of wire 'singing'
in harmony with the constellations of energy that
are harmonic multiples of the resonant frequency.
What happens to that energy? If you've got a feeding
attached at the current node, you can suck of a substantial
part of that energy and route it someplace else . . . like
your VOR receiver.
But unless there is a feed line, energy exciting
the antenna will be rejected as heat from ohmic
losses at the current node or re-radiated. After
all, it HAS to go somewhere.
So what about those little bits of metal suspended in
an otherwise non-conductive paint? I suspect that a
really 'chunky' filling (0.001") flakes would be
the largest practical filler. What portion of a wavelength
is 0.001" compared to the wavelength of the comm
transceiver or even GPS?
Pretty small. This suggests that the currents induced
in such particles at our frequencies of interest are
vanishingly small, i.e. insignificant. These particles
ARE significant at wavelengths of light, hence effective
modifiers for those electromagnetic fields. However,
I suspect that there are no measurable effects for such
particles at our frequencies of interest.
Particle sizes are simply too far removed from resonance where
significant currents would be induced. No current,
no heat, no re-radiation, no measurable effects.
It's an easy experiment to conduct and I have the equipment
to do it . . . just no time at the moment and I'll need
to acquire some exemplar coatings to test.
If anyone is aware of quantified studies conducted on
this topic, I'd be grateful for some linkage. Anyone
conversant in an alternative explanation is encouraged
to correct my mis-conception . . .
Bob . . .
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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rv10pro(at)gmail.com
Guest
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| Posted: Tue Jun 19, 2018 11:16 am Post subject: Paint question |
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Lost navigation on one of our Bombardier Q400s. On researching the circuitry wiring, components and attachments. We found a paint shop had forgotten to mask the antenna's. That was Azko White..... no metallic. Your mileage may vary. Paint can have an attenuation factor. Good Luck. New unpainted antennas on the port and starboard side of the Vertical corrected the problem. Â
could it have been corrosion from the antenna mount to the skin of the Vertical. Mark it up the the incredible job I did preparing the replacement antenna installation if you want to go there.
John Cox
On Tue, Jun 19, 2018 at 12:01 PM Ernest Christley <echristley(at)att.net (echristley(at)att.net)> wrote:
| Quote: | If I'm not mistaken, Jim Weir did these experiments and documented them in his antennae booklet. I may be wrong, since it was years ago that I went through them, but I'm pretty sure that he even included a diagram.
On Tuesday, June 19, 2018 2:05 PM, "Robert L. Nuckolls, III" <nuckolls.bob(at)a4443518791543424097y_msg_container"> | Quote: | | I hate paint, and I'm certainly no expert. But I'd bet that the only paints that contain enough metal to be an RF issue would be the 'silver' step of fabric coatings, some of which (likely all the old stuff) contain aluminum dust as a UV blocker, and paints specifically sold as metallic and/or metalflake colors. |
 I am skeptical of the claimed effects for metallic
 particles in the paint. Intuitively, one can easily
 accept that placing conductive/refractive materials
 in the path of an electromagnetic wave will have
 some 'effect' . . . but to what degree?
 In electromagnetic compatibility schools we're taught
 that 'breaks in shields should be kept to 1/10th
 wavelength at frequency of interest to avoid degrading
 that shield's effectiveness'.
 We've seen reflectors for centimeter wave, dish
 antennas made from metallic mesh with significant
 openings . . . yet so small compared to the wavelength
 of the operating frequency as to behave as a solid
 surface.
 When you place a conductor (like a dipole antenna)
 out in the air and exposed it to some EM field,
 then energy at the frequency where the antenna is
 resonant will excite the antenna and manifest with
 a strong current node in the middle and voltage nodes
 at the ends.
 Now, you've got the 1/2 wave piece of wire 'singing'
 in harmony with the constellations of energy that
 are harmonic multiples of the resonant frequency.
 What happens to that energy? If you've got a feeding
 attached at the current node, you can suck of a substantial
 part of that energy and route it someplace else . . . like
 your VOR receiver.
 But unless there is a feed line, energy exciting
 the antenna will be rejected as heat from ohmic
 losses at the current node or re-radiated. After
 all, it HAS to go somewhere.
 So what about those little bits of metal suspended in
 an otherwise non-conductive paint? I suspect that a
 really 'chunky' filling (0.001") flakes would be
 the largest practical filler. What portion of a wavelength
 is 0.001" compared to the wavelength of the comm
 transceiver or even GPS?
 Pretty small. This suggests that the currents induced
 in such particles at our frequencies of interest are
 vanishingly small, i.e. insignificant. These particles
 ARE significant at wavelengths of light, hence effective
 modifiers for those electromagnetic fields. However,
 I suspect that there are no measurable effects for such
 particles at our frequencies of interest.
 Particle sizes are simply too far removed from resonance where
 significant currents would be induced. No current,
 no heat, no re-radiation, no measurable effects.
 It's an easy experiment to conduct and I have the equipment
 to do it . . . just no time at the moment and I'll need
 to acquire some exemplar coatings to test.
 If anyone is aware of quantified studies conducted on
 this topic, I'd be grateful for some linkage. Anyone
 conversant in an alternative explanation is encouraged
 to correct my mis-conception . . .Â
 Bob . . .
|
--
Johnny C.
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Tue Jun 19, 2018 11:19 am Post subject: Paint question |
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Bob:
You are 100% correct!
The reason why you are told not to paint Antennas especially GPS Antennas with any paint and especially Metal Flake paint is:
After you go back to the Manufacture and say: My GPS has weak reception, whats wrong? Â
The Manufacture will ask what color is your plane? And, when you say Candy Apple Red with Gold Flake. Â
The Manufacture will say: You are NOT ALLOWED to paint the Antennas and ESPECIALLY not in Metal Flake... Go Strip Your Plane! I TOLD YOU NOT TO PAINT THE ANTENNAS!!! I wash my hands of the problem until you STRIP your plane.
When all else fails - Blame the Pilot/Builder!
Barry
On Tue, Jun 19, 2018 at 2:03 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | | Quote: | | I hate paint, and I'm certainly no expert. But I'd bet that the only paints that contain enough metal to be an RF issue would be the 'silver' step of fabric coatings, some of which (likely all the old stuff) contain aluminum dust as a UV blocker, and paints specifically sold as metallic and/or metalflake colors. |
 I am skeptical of the claimed effects for metallic
 particles in the paint. Intuitively, one can easily
 accept that placing conductive/refractive materials
 in the path of an electromagnetic wave will have
 some 'effect' . . . but to what degree?
 In electromagnetic compatibility schools we're taught
 that 'breaks in shields should be kept to 1/10th
 wavelength at frequency of interest to avoid degrading
 that shield's effectiveness'.
 We've seen reflectors for centimeter wave, dish
 antennas made from metallic mesh with significant
 openings . . . yet so small compared to the wavelength
 of the operating frequency as to behave as a solid
 surface.
 When you place a conductor (like a dipole antenna)
 out in the air and exposed it to some EM field,
 then energy at the frequency where the antenna is
 resonant will excite the antenna and manifest with
 a strong current node in the middle and voltage nodes
 at the ends.
 Now, you've got the 1/2 wave piece of wire 'singing'
 in harmony with the constellations of energy that
 are harmonic multiples of the resonant frequency.
 What happens to that energy? If you've got a feeding
 attached at the current node, you can suck of a substantial
 part of that energy and route it someplace else . . . like
 your VOR receiver.
 But unless there is a feed line, energy exciting
 the antenna will be rejected as heat from ohmic
 losses at the current node or re-radiated. After
 all, it HAS to go somewhere.
 So what about those little bits of metal suspended in
 an otherwise non-conductive paint? I suspect that a
 really 'chunky' filling (0.001") flakes would be
 the largest practical filler. What portion of a wavelength
 is 0.001" compared to the wavelength of the comm
 transceiver or even GPS?
 Pretty small. This suggests that the currents induced
 in such particles at our frequencies of interest are
 vanishingly small, i.e. insignificant. These particles
 ARE significant at wavelengths of light, hence effective
 modifiers for those electromagnetic fields. However,
 I suspect that there are no measurable effects for such
 particles at our frequencies of interest.
 Particle sizes are simply too far removed from resonance where
 significant currents would be induced. No current,
 no heat, no re-radiation, no measurable effects.
 It's an easy experiment to conduct and I have the equipment
 to do it . . . just no time at the moment and I'll need
 to acquire some exemplar coatings to test.
 If anyone is aware of quantified studies conducted on
 this topic, I'd be grateful for some linkage. Anyone
 conversant in an alternative explanation is encouraged
 to correct my mis-conception . . .Â
 Bob . . .
|
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cluros(at)gmail.com
Guest
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| Posted: Tue Jun 19, 2018 11:46 am Post subject: Paint question |
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|
A few years ago someone gave me an old Cessna VHF antenna which was all pitted and looked like hell. After checking with my avionics guy I sanded it a bit and painted it with plastic paint. The performance is not always perfect but I always assumed that is because it is too close to the ELT antenna. Is painting fiberglass antennas a no-no?
On Tue, Jun 19, 2018 at 12:15 PM, John Cox <rv10pro(at)gmail.com (rv10pro(at)gmail.com)> wrote:
| Quote: | Lost navigation on one of our Bombardier Q400s. On researching the circuitry wiring, components and attachments. We found a paint shop had forgotten to mask the antenna's. That was Azko White..... no metallic. Your mileage may vary. Paint can have an attenuation factor. Good Luck. New unpainted antennas on the port and starboard side of the Vertical corrected the problem. Â
could it have been corrosion from the antenna mount to the skin of the Vertical. Mark it up the the incredible job I did preparing the replacement antenna installation if you want to go there.
John Cox
On Tue, Jun 19, 2018 at 12:01 PM Ernest Christley <echristley(at)att.net (echristley(at)att.net)> wrote:
| Quote: | If I'm not mistaken, Jim Weir did these experiments and documented them in his antennae booklet. I may be wrong, since it was years ago that I went through them, but I'm pretty sure that he even included a diagram.
On Tuesday, June 19, 2018 2:05 PM, "Robert L. Nuckolls, III" <nuckolls.bob(at)a4443518791543424097y_msg_container"> (nuckolls.bob(at)aeroelectric.com) (nuckolls.bob(at)aeroelectric.com) (nuckolls.bob(at)aeroelectric.com) (nuckolls.bob(at)aeroelectric.com) | Quote: | | I hate paint, and I'm certainly no expert. But I'd bet that the only paints that contain enough metal to be an RF issue would be the 'silver' step of fabric coatings, some of which (likely all the old stuff) contain aluminum dust as a UV blocker, and paints specifically sold as metallic and/or metalflake colors. |
 I am skeptical of the claimed effects for metallic
 particles in the paint. Intuitively, one can easily
 accept that placing conductive/refractive materials
 in the path of an electromagnetic wave will have
 some 'effect' . . . but to what degree?
 In electromagnetic compatibility schools we're taught
 that 'breaks in shields should be kept to 1/10th
 wavelength at frequency of interest to avoid degrading
 that shield's effectiveness'.
 We've seen reflectors for centimeter wave, dish
 antennas made from metallic mesh with significant
 openings . . . yet so small compared to the wavelength
 of the operating frequency as to behave as a solid
 surface.
 When you place a conductor (like a dipole antenna)
 out in the air and exposed it to some EM field,
 then energy at the frequency where the antenna is
 resonant will excite the antenna and manifest with
 a strong current node in the middle and voltage nodes
 at the ends.
 Now, you've got the 1/2 wave piece of wire 'singing'
 in harmony with the constellations of energy that
 are harmonic multiples of the resonant frequency.
 What happens to that energy? If you've got a feeding
 attached at the current node, you can suck of a substantial
 part of that energy and route it someplace else . . . like
 your VOR receiver.
 But unless there is a feed line, energy exciting
 the antenna will be rejected as heat from ohmic
 losses at the current node or re-radiated. After
 all, it HAS to go somewhere.
 So what about those little bits of metal suspended in
 an otherwise non-conductive paint? I suspect that a
 really 'chunky' filling (0.001") flakes would be
 the largest practical filler. What portion of a wavelength
 is 0.001" compared to the wavelength of the comm
 transceiver or even GPS?
 Pretty small. This suggests that the currents induced
 in such particles at our frequencies of interest are
 vanishingly small, i.e. insignificant. These particles
 ARE significant at wavelengths of light, hence effective
 modifiers for those electromagnetic fields. However,
 I suspect that there are no measurable effects for such
 particles at our frequencies of interest.
 Particle sizes are simply too far removed from resonance where
 significant currents would be induced. No current,
 no heat, no re-radiation, no measurable effects.
 It's an easy experiment to conduct and I have the equipment
 to do it . . . just no time at the moment and I'll need
 to acquire some exemplar coatings to test.
 If anyone is aware of quantified studies conducted on
 this topic, I'd be grateful for some linkage. Anyone
 conversant in an alternative explanation is encouraged
 to correct my mis-conception . . .Â
 Bob . . .
|
--
Johnny C.
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Kellym
Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ
|
| Posted: Tue Jun 19, 2018 12:23 pm Post subject: Paint question |
|
|
A friend built a very nice RV-7 (featured on cover of AS catalog a few
years ago.) It is bare aluminum, with the wing tips painted with very
metallic aluminum color over the fiberglass. It has Archer nav and com
antennas in the wingtips. Prior to painting the antennas performed
acceptably, if maybe 30% less range than external antennas. After
painting the antennas had perhaps a 10 mile or less range, which forced
installing an external com antenna.
Kelly
On 6/19/2018 11:56 AM, Ernest Christley wrote:
| Quote: | If I'm not mistaken, Jim Weir did these experiments and documented them
in his antennae booklet. I may be wrong, since it was years ago that I
went through them, but I'm pretty sure that he even included a diagram.
On Tuesday, June 19, 2018 2:05 PM, "Robert L. Nuckolls, III"
<nuckolls.bob(at)aeroelectric.com> wrote:
> I hate paint, and I'm certainly no expert. But I'd bet that the only
> paints that contain enough metal to be an RF issue would be the
> 'silver' step of fabric coatings, some of which (likely all the old
> stuff) contain aluminum dust as a UV blocker, and paints specifically
> sold as metallic and/or metalflake colors.
 I am skeptical of the claimed effects for metallic
 particles in the paint. Intuitively, one can easily
 accept that placing conductive/refractive materials
 in the path of an electromagnetic wave will have
 some 'effect' . . . but to what degree?
 In electromagnetic compatibility schools we're taught
 that 'breaks in shields should be kept to 1/10th
 wavelength at frequency of interest to avoid degrading
 that shield's effectiveness'.
 We've seen reflectors for centimeter wave, dish
 antennas made from metallic mesh with significant
 openings . . . yet so small compared to the wavelength
 of the operating frequency as to behave as a solid
 surface.
 When you place a conductor (like a dipole antenna)
 out in the air and exposed it to some EM field,
 then energy at the frequency where the antenna is
 resonant will excite the antenna and manifest with
 a strong current node in the middle and voltage nodes
 at the ends.
 Now, you've got the 1/2 wave piece of wire 'singing'
 in harmony with the constellations of energy that
 are harmonic multiples of the resonant frequency.
 What happens to that energy? If you've got a feeding
 attached at the current node, you can suck of a substantial
 part of that energy and route it someplace else . . . like
 your VOR receiver.
 But unless there is a feed line, energy exciting
 the antenna will be rejected as heat from ohmic
 losses at the current node or re-radiated. After
 all, it HAS to go somewhere.
 So what about those little bits of metal suspended in
 an otherwise non-conductive paint? I suspect that a
 really 'chunky' filling (0.001") flakes would be
 the largest practical filler. What portion of a wavelength
 is 0.001" compared to the wavelength of the comm
 transceiver or even GPS?
 Pretty small. This suggests that the currents induced
 in such particles at our frequencies of interest are
 vanishingly small, i.e. insignificant. These particles
 ARE significant at wavelengths of light, hence effective
 modifiers for those electromagnetic fields. However,
 I suspect that there are no measurable effects for such
 particles at our frequencies of interest.
 Particle sizes are simply too far removed from resonance where
 significant currents would be induced. No current,
 no heat, no re-radiation, no measurable effects.
 It's an easy experiment to conduct and I have the equipment
 to do it . . . just no time at the moment and I'll need
 to acquire some exemplar coatings to test.
 If anyone is aware of quantified studies conducted on
 this topic, I'd be grateful for some linkage. Anyone
 conversant in an alternative explanation is encouraged
 to correct my mis-conception . . .
<https://mail.yahoo.com/neo/launch?.src=ym&reason=myc&soc_src=mail&soc_trk=ma#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
 Bob . . .
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A&P/IA, EAA Tech Counselor # 5286
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stuart(at)stuarthutchison
Guest
|
| Posted: Wed Jun 20, 2018 3:02 am Post subject: Paint question |
|
|
G’day Bob.
I’m building a 200KTAS aeroplane, so very reluctant to put anything out in the breeze that I don’t have to. I mounted my Garmin and Dynon GPS antennas under the windscreen, but being white they will surely cause unwanted reflections. I intend to test some different things, but first option was to tack some black stockings under the dash mat and slip that over both antennas. I suppose black stockings are darkened with carbon, so there may be some attenuation, but if there is it should be immediately visible on the signal strength bar graphs on screen. Alternatives are black tissue paper and a very light coat of matt black paint as a last resort. It might take me a few weeks to muster the courage to walk in store to buy black stockings, but will come back the forum with some observations soon.
Kind regards, Stu | Quote: | On 20 Jun 2018, at 04:03, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | | I hate paint, and I'm certainly no expert. But I'd bet that the only paints that contain enough metal to be an RF issue would be the 'silver' step of fabric coatings, some of which (likely all the old stuff) contain aluminum dust as a UV blocker, and paints specifically sold as metallic and/or metalflake colors. |
I am skeptical of the claimed effects for metallic particles in the paint. Intuitively, one can easily accept that placing conductive/refractive materials in the path of an electromagnetic wave will have some 'effect' . . . but to what degree? In electromagnetic compatibility schools we're taught that 'breaks in shields should be kept to 1/10th wavelength at frequency of interest to avoid degrading that shield's effectiveness'. We've seen reflectors for centimeter wave, dish antennas made from metallic mesh with significant openings . . . yet so small compared to the wavelength of the operating frequency as to behave as a solid surface. When you place a conductor (like a dipole antenna) out in the air and exposed it to some EM field, then energy at the frequency where the antenna is resonant will excite the antenna and manifest with a strong current node in the middle and voltage nodes at the ends. Now, you've got the 1/2 wave piece of wire 'singing' in harmony with the constellations of energy that are harmonic multiples of the resonant frequency. What happens to that energy? If you've got a feeding attached at the current node, you can suck of a substantial part of that energy and route it someplace else . . . like your VOR receiver. But unless there is a feed line, energy exciting the antenna will be rejected as heat from ohmic losses at the current node or re-radiated. After all, it HAS to go somewhere. So what about those little bits of metal suspended in an otherwise non-conductive paint? I suspect that a really 'chunky' filling (0.001") flakes would be the largest practical filler. What portion of a wavelength is 0.001" compared to the wavelength of the comm transceiver or even GPS? Pretty small. This suggests that the currents induced in such particles at our frequencies of interest are vanishingly small, i.e. insignificant. These particles ARE significant at wavelengths of light, hence effective modifiers for those electromagnetic fields. However, I suspect that there are no measurable effects for such particles at our frequencies of interest. Particle sizes are simply too far removed from resonance where significant currents would be induced. No current, no heat, no re-radiation, no measurable effects. It's an easy experiment to conduct and I have the equipment to do it . . . just no time at the moment and I'll need to acquire some exemplar coatings to test. If anyone is aware of quantified studies conducted on this topic, I'd be grateful for some linkage. Anyone conversant in an alternative explanation is encouraged to correct my mis-conception . . . [url=x-msg://3/#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2] [/url]
Bob . . .
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mapratherid(at)gmail.com
Guest
|
| Posted: Wed Jun 20, 2018 4:57 am Post subject: Paint question |
|
|
Hi Bob,Long time no contact... I’m happy you’re still in this game!
Regarding this topic, I wonder how much the the conductive bits are in contact with each other. I don’t know how isolated each bit of conductive material is in such a paint, but I could imagine there could be billions of contacts between neighboring bits of flake or powder such that there would be a random resistive path across the painted surface. So, maybe it’s not a constellation of very small dipoles, but a very large, random, resistive network? Maybe that’s an easy theory to test - use an ohmmeter to check how much conductivity there is across a painted surface? Might have to dig the probes around to get contact?
As far as non-metallic paint on antennas, I wonder if that’s a detuning effect because of changing the dielectric...
Regards,
Matt Prather
Sent from my iPhone
On Jun 19, 2018, at 12:56 PM, Ernest Christley <echristley(at)att.net (echristley(at)att.net)> wrote:
| Quote: | If I'm not mistaken, Jim Weir did these experiments and documented them in his antennae booklet. I may be wrong, since it was years ago that I went through them, but I'm pretty sure that he even included a diagram.
On Tuesday, June 19, 2018 2:05 PM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | | I hate paint, and I'm certainly no expert. But I'd bet that the only paints that contain enough metal to be an RF issue would be the 'silver' step of fabric coatings, some of which (likely all the old stuff) contain aluminum dust as a UV blocker, and paints specifically sold as metallic and/or metalflake colors. |
I am skeptical of the claimed effects for metallic
particles in the paint. Intuitively, one can easily
accept that placing conductive/refractive materials
in the path of an electromagnetic wave will have
some 'effect' . . . but to what degree?
In electromagnetic compatibility schools we're taught
that 'breaks in shields should be kept to 1/10th
wavelength at frequency of interest to avoid degrading
that shield's effectiveness'.
We've seen reflectors for centimeter wave, dish
antennas made from metallic mesh with significant
openings . . . yet so small compared to the wavelength
of the operating frequency as to behave as a solid
surface.
When you place a conductor (like a dipole antenna)
out in the air and exposed it to some EM field,
then energy at the frequency where the antenna is
resonant will excite the antenna and manifest with
a strong current node in the middle and voltage nodes
at the ends.
Now, you've got the 1/2 wave piece of wire 'singing'
in harmony with the constellations of energy that
are harmonic multiples of the resonant frequency.
What happens to that energy? If you've got a feeding
attached at the current node, you can suck of a substantial
part of that energy and route it someplace else . . . like
your VOR receiver.
But unless there is a feed line, energy exciting
the antenna will be rejected as heat from ohmic
losses at the current node or re-radiated. After
all, it HAS to go somewhere.
So what about those little bits of metal suspended in
an otherwise non-conductive paint? I suspect that a
really 'chunky' filling (0.001") flakes would be
the largest practical filler. What portion of a wavelength
is 0.001" compared to the wavelength of the comm
transceiver or even GPS?
Pretty small. This suggests that the currents induced
in such particles at our frequencies of interest are
vanishingly small, i.e. insignificant. These particles
ARE significant at wavelengths of light, hence effective
modifiers for those electromagnetic fields. However,
I suspect that there are no measurable effects for such
particles at our frequencies of interest.
Particle sizes are simply too far removed from resonance where
significant currents would be induced. No current,
no heat, no re-radiation, no measurable effects.
It's an easy experiment to conduct and I have the equipment
to do it . . . just no time at the moment and I'll need
to acquire some exemplar coatings to test.
If anyone is aware of quantified studies conducted on
this topic, I'd be grateful for some linkage. Anyone
conversant in an alternative explanation is encouraged
to correct my mis-conception . . .
Bob . . .
|
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nuckolls.bob(at)aeroelect
Guest
|
| Posted: Wed Jun 20, 2018 6:47 am Post subject: Paint question |
|
|
At 07:56 AM 6/20/2018, you wrote:
| Quote: | Hi Bob,
Long time no contact... I’m happy you’re still in this game!
Regarding this topic, I wonder how much the the conductive bits are in contact with each other. I don’t know how isolated each bit of conductive material is in such a paint, but I could imagine there could be billions of contacts between neighboring bits of flake or powder such that there would be a random resistive path across the painted surface. So, maybe it’s not a constellation of very small dipoles, but a very large, random, resistive network? Maybe that’s an easy theory to test - use an ohmmeter to check how much conductivity there is across a painted surface? Might have to dig the probes around to get contact? |
Interesting hypothesis . . . I'm day-dreaming
a methodology for testing various coatings
as 'shields' . . .
| Quote: | | As far as non-metallic paint on antennas, I wonder if that’s a detuning effect because of changing the dielectric... |
A valid hypothesis I think. I've been supplying
antennas to folks in the local prescribed burn
and fire fighting associations. There's a
product sold on eBay fabricated from 'ladder
line' that performs as a dual band (VHF/UHF)
antenna. I housed one in a piece of 1" thinwall
pvc but disappointed to find that the center
frequencies moved down about 10%.
The antenna was 'snug' in the pipl.
Tried a piece of 2" and things got
better . . . ~5% downshift. Hmmm . . .
getting ready to try a 3" piece with
spacers designed to hold the antenna central
to the radome. I'm betting this is going
to be 'the answer' but not the solution.
Wind-loading for so large a radome complicates
the support structures. I can use this antenna
on the little antenna farm on my roof but not
on top of a 30 foot mast in the Kansas winter
ice and all the time winds. I've ordered materials
to built all metal dual band antennas of this
configuration.
[img]cid:.0[/img]
No radome necessary.
So I think your dielectric proximity idea is not without
merit . . .
Bob . . .
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Thu Jun 21, 2018 7:23 am Post subject: Paint question |
|
|
At 11:54 AM 6/20/2018, you wrote:
| Quote: | Bob,
You’ll like the antenna you have pictured, I believe. I have been using a home-brewed version of that antenna now for several years and I love it as a dual-band antenna. |
Pleased to hear it. I've been aware of this design
for some years but never had an opportunity/need
to try it. Some of our local volunteer fire crews are
interested in outdoor antennas for their radios that
will cover both the MURS/GMRS frequencies which are,
like 2M/70CM, harmonically related.
Best yet, this is an antenna they can build themselves.
Basic cut, drill, thread and assemble. I don't have
to get into the hammer-n-tongs loop!
Bob . . .
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Thu Jun 21, 2018 8:00 am Post subject: Paint question |
|
|
At 09:46 AM 6/20/2018, you wrote:
| Quote: | At 07:56 AM 6/20/2018, you wrote:
| Quote: | Hi Bob,
Long time no contact... I’m happy you’re still in this game!
Regarding this topic, I wonder how much the the conductive bits are in contact with each other. I don’t know how isolated each bit of conductive material is in such a paint, but I could imagine there could be billions of contacts between neighboring bits of flake or powder such that there would be a random resistive path across the painted surface. |
|
I've been doing some 'asphalt contemplation' on a simple
test setup to evaluate the effects of various paints/coatings
on antenna performance.
I was trying to imagine how conductive particles suspended
in a non-conductive 'solution' would achieve a
microscopic version of the gas-tight contact needed
for reliable connection between conductors. It seems
that surface tension would cause each particle to
be totally enveloped, thus prevented from making
physical contact with other particles.
Not sure about what happens as the solution becomes
a solid when solvents evaporate and the paint dries.
I've seen volume resistivity measurements on some
coatings/fillers, like potting compounds. These
are always VERY high . . . including those designed
for thermal conductivity.
I'm thinking that there are three potential effects
of paint . . . the dielectric effects you hypothesized
which would probably be limited to a lowering of
resonant frequency, the shielding effects which
block and or re-direct the wave fronts of interest
and attenuation/dissipation effects that simply
turn the RF energy into heat.
I'm recalling a bit of a fire drill on the ELT
transmitters for Beechjets where a new version
of the ELT kept tripping off due to high SWR
on the VHF antenna. Seems the older version happily
existed with a pair of antennas tucked under
the fairing at the root of vertical fin leading
edge.
[img]cid:.0[/img]
Oookkaaay . . .
Now, let's lay the VHF antenna back so that it
sorta conforms to the inside of the fairing . . .
except . . .
Fairing was also part of an air-intake ductwork
for the A/C . . . so the antennas wound up
looking like this:
[img]cid:.1[/img]
There were metallic braces inside the
fairing along with bond straps that tied
the braces to airframe . . . for lighting
effects. Added on top of all this was a
composite fairing material . . .
capped off with paint often chosen by
the customer hence of uncontrolled pedigree.
What's a poor ELT transmitter to do?
[img]cid:.2[/img]
I couldn't find anywhere in the archives where
this installation had been measured for
performance . . . a condition that didn't
raise its ugly head until a new ELT complained
about an 'unsatisfactory' antenna.
I suggested we design a new, top loaded vertical
for the VHF antenna that remained vertical with
better separation from the effects of overhead
structures.
[img]cid:.3[/img]
Further, we could fine tune the antenna to accommodate
any residual effects from proximity of other structures.
This got the flying fuzz all in a dither . . . a new
antenna would violate the TSO on the ELT . . . but
abusing the TSO'd antenna did not . . . go figure.
I think they wound up widening the SWR trip tolerances
on the ELT transmitter.
Not one of my happier experiences with the bureaucracy.
Bob . . .
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mapratherid(at)gmail.com
Guest
|
| Posted: Fri Jun 29, 2018 7:49 pm Post subject: Paint question |
|
|
Good point about the surface tension effect causing the conductive particles to be completely covered and surrounded...
And, any detuning effect is probably limited - can’t lower the resonant frequency of particles from GHz (?) to MHz...
How about capacitive coupling of one particle to the next? Capacitance has Area in the numerator and distance in the denominator... Probably not much there - the A is to small and the d too large. Hmm.
Regards,
Matt Prather
On Jun 21, 2018, at 8:59 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | At 09:46 AM 6/20/2018, you wrote:
| Quote: | At 07:56 AM 6/20/2018, you wrote:
| Quote: | Hi Bob,
Long time no contact... I’m happy you’re still in this game!
Regarding this topic, I wonder how much the the conductive bits are in contact with each other. I don’t know how isolated each bit of conductive material is in such a paint, but I could imagine there could be billions of contacts between neighboring bits of flake or powder such that there would be a random resistive path across the painted surface. |
|
I've been doing some 'asphalt contemplation' on a simple
test setup to evaluate the effects of various paints/coatings
on antenna performance.
I was trying to imagine how conductive particles suspended
in a non-conductive 'solution' would achieve a
microscopic version of the gas-tight contact needed
for reliable connection between conductors. It seems
that surface tension would cause each particle to
be totally enveloped, thus prevented from making
physical contact with other particles.
Not sure about what happens as the solution becomes
a solid when solvents evaporate and the paint dries.
I've seen volume resistivity measurements on some
coatings/fillers, like potting compounds. These
are always VERY high . . . including those designed
for thermal conductivity.
I'm thinking that there are three potential effects
of paint . . . the dielectric effects you hypothesized
which would probably be limited to a lowering of
resonant frequency, the shielding effects which
block and or re-direct the wave fronts of interest
and attenuation/dissipation effects that simply
turn the RF energy into heat.
I'm recalling a bit of a fire drill on the ELT
transmitters for Beechjets where a new version
of the ELT kept tripping off due to high SWR
on the VHF antenna. Seems the older version happily
existed with a pair of antennas tucked under
the fairing at the root of vertical fin leading
edge.
<25ac6ff7.jpg>
Oookkaaay . . .
Now, let's lay the VHF antenna back so that it
sorta conforms to the inside of the fairing . . .
except . . .
Fairing was also part of an air-intake ductwork
for the A/C . . . so the antennas wound up
looking like this:
<25ac7006.jpg>
There were metallic braces inside the
fairing along with bond straps that tied
the braces to airframe . . . for lighting
effects. Added on top of all this was a
composite fairing material . . .
capped off with paint often chosen by
the customer hence of uncontrolled pedigree.
What's a poor ELT transmitter to do?
<25ac7016.jpg>
I couldn't find anywhere in the archives where
this installation had been measured for
performance . . . a condition that didn't
raise its ugly head until a new ELT complained
about an 'unsatisfactory' antenna.
I suggested we design a new, top loaded vertical
for the VHF antenna that remained vertical with
better separation from the effects of overhead
structures.
<25ac7026.jpg>
Further, we could fine tune the antenna to accommodate
any residual effects from proximity of other structures.
This got the flying fuzz all in a dither . . . a new
antenna would violate the TSO on the ELT . . . but
abusing the TSO'd antenna did not . . . go figure.
I think they wound up widening the SWR trip tolerances
on the ELT transmitter.
Not one of my happier experiences with the bureaucracy.
Bob . . .
|
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