Today's Message Index:
----------------------
1. 05:39 AM - Re: Alternator Noise When Touching Metal Airframe Grounds (Jared Yates)
2. 06:02 AM - Re: Alternator Noise When Touching Metal Airframe Grounds (Kelly McMullen)
3. 06:03 AM - Re: Alternator Noise When Touching Metal Airframe Grounds (Robert L. Nuckolls, III)
4. 07:38 AM - Re: Alternator Noise When Touching Metal Airframe Grounds (Jared Yates)
5. 11:03 AM - Re: Paint question (Robert L. Nuckolls, III)
6. 11:07 AM - Re: Alternator Noise When Touching Metal Airframe Grounds (Robert L. Nuckolls, III)
7. 11:28 AM - Re: Alternator Noise When Touching Metal Airframe Grounds (Roger)
8. 11:30 AM - Re: Alternator Noise When Touching Metal Airframe Grounds (don van santen)
9. 11:57 AM - Re: Paint question (Ernest Christley)
10. 12:16 PM - Re: Paint question (John Cox)
11. 12:19 PM - Re: Paint question (FLYaDIVE)
12. 12:46 PM - Re: Paint question (Sebastien)
13. 01:23 PM - Re: Paint question (Kelly McMullen)
Message 1
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| Subject: | Re: Alternator Noise When Touching Metal Airframe Grounds |
Yes, ANR heAdsets powered by the airplane electrical system.
On June 18, 2018 16:57:36 "Robert L. Nuckolls, III"
<nuckolls.bob@aeroelectric.com> wrote:
> At 02:16 PM 6/18/2018, you wrote:
>
>> Thanks Bob and everyone, I'm
>> back with new data, having returned to the airplane and flown it
>> today.
>>
>> Disregard what I said before about the volume- the noise is not impacted
>> by the local headset volume or by the intercom volume, or the 430 volume.
>> It seems to be not adjustable at all. It does not seem to be present when
>> the engine is not running, but then again the alternator noise is the
>> majority of the noise, and it would not be present with the engine
>> off.
>
>
> Are these headsets noise canceling? I.e. fitted with
> electronics of some kind? I was looking for Bose X
> Model info on the 'net with no success for the quick
> look-see.
>
>
> Bob . . .
Message 2
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| Subject: | Re: Alternator Noise When Touching Metal Airframe |
Grounds
I don't think that is the question, and no, most ANR headsets are NOT
powered by the aircraft electrics...most are battery powered, only those
with a LEMO plug are aircraft powered.
Nonetheless, ANR circuitry can be affected by extraneous RF.
On 6/19/2018 5:37 AM, Jared Yates wrote:
> Yes, ANR heAdsets powered by the airplane electrical system.
>
> On June 18, 2018 16:57:36 "Robert L. Nuckolls, III"
> <nuckolls.bob@aeroelectric.com> wrote:
>> Are these headsets noise canceling? I.e. fitted with
>> electronics of some kind? I was looking for Bose X
>> Model info on the 'net with no success for the quick
>> look-see.
>>
>>
>> Bob . . .
>>
>
Message 3
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| Subject: | Re: Alternator Noise When Touching Metal Airframe |
Grounds
At 07:37 AM 6/19/2018, you wrote:
>Yes, ANR heAdsets powered by the airplane electrical system.
Okay, do I correctly interpret that your
audio system is capable of using either
the Bose X or say a plain vanilla headset?
The fact that your noise is affected by
changes in body conduction suggests that the
stimulus is entering the system through
those spaces in close proximity to your
bod . . . like the things clamped on your
head?
Try another headset if you can . . .
Bob . . .
Message 4
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| Subject: | Re: Alternator Noise When Touching Metal Airframe Grounds |
Good suggestion, thanks. So far all 4 lemo sets are the same. I have a dual
plug version of the same bose to try, and can do that and report back.
On June 19, 2018 09:10:19 "Robert L. Nuckolls, III"
<nuckolls.bob@aeroelectric.com> wrote:
> At 07:37 AM 6/19/2018, you wrote:
>
>> Yes, ANR heAdsets powered by the
>> airplane electrical system.
>
>
> Okay, do I correctly interpret that your
> audio system is capable of using either
> the Bose X or say a plain vanilla headset?
>
> The fact that your noise is affected by
> changes in body conduction suggests that the
> stimulus is entering the system through
> those spaces in close proximity to your
> bod . . . like the things clamped on your
> head?
>
> Try another headset if you can . . .
>
>
> Bob . . .
Message 5
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| Subject: | Re: Paint question |
>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 . . .
Message 6
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| Subject: | Re: Alternator Noise When Touching Metal Airframe |
Grounds
At 09:36 AM 6/19/2018, you wrote:
>Good suggestion, thanks. So far all 4 lemo sets are the same. I have
>a dual plug version of the same bose to try, and can do that and report back
Hmmmm . . . not sure I've got an accurate image
of the differences between 'lemo' and 'dual plug'.
Does this described the connectors at the end
of the headset cord . . . single mulit-pin as opposed
to "Y" plugs?
To be significant, the test headset needs to
be a generic, non-electronic . . . but go
ahead and try the dual-plug Bose X too.
Bob . . .
Message 7
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| Subject: | Alternator Noise When Touching Metal Airframe |
Grounds
Is the noise still present when the ANR is turned off?
Roger
At 09:36 AM 6/19/2018, you wrote:
Good suggestion, thanks. So far all 4 lemo sets are the same. I have a dual
plug version of the same bose to try, and can do that and report back
=C2- Hmmmm . . . not sure I've got an accurate image
=C2- of the differences between 'lemo' and 'dual plug'.
=C2- Does this described the connectors at the end
=C2- of the headset cord . . . single mulit-pin as opposed
=C2- to "Y" plugs?
=C2- To be significant, the test headset needs to
=C2- be a generic, non-electronic . . . but go
=C2- ahead and try the dual-plug Bose X too.
=C2- Bob . . .
Message 8
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| Subject: | Re: Alternator Noise When Touching Metal Airframe Grounds |
A lemo plug has mic and audio plus the power in one plug. These are not
phone jack type plugs. The dual plugs are the typical phone jack with the
audio and mic cables seperate, also no power.
On Tue, Jun 19, 2018, 11:12 Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 09:36 AM 6/19/2018, you wrote:
>
> Good suggestion, thanks. So far all 4 lemo sets are the same. I have a
> dual plug version of the same bose to try, and can do that and report back
>
>
> Hmmmm . . . not sure I've got an accurate image
> of the differences between 'lemo' and 'dual plug'.
> Does this described the connectors at the end
> of the headset cord . . . single mulit-pin as opposed
> to "Y" plugs?
>
> To be significant, the test headset needs to
> be a generic, non-electronic . . . but go
> ahead and try the dual-plug Bose X too.
>
>
> Bob . . .
>
Message 9
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| Subject: | Re: Paint question |
If I'm not mistaken, Jim Weir did these experiments and documented them in
his antennae booklet.=C2- I may be wrong, since it was years ago that I w
ent 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@aeroelectric.com> wrote:
I hate paint, andI'm certainly no expert. But I'd bet that the only paints
that containenough metal to be an RF issue would be the 'silver' step of fa
briccoatings, some of which (likely all the old stuff) contain aluminum dus
tas a UV blocker, and paints specifically sold as metallic and/ormetalflake
colors.
=C2- I am skeptical of the claimed effects for metallic
=C2- particles in the paint. Intuitively, one can easily
=C2- accept that placing conductive/refractive materials
=C2- in the path of an electromagnetic wave will have
=C2- some 'effect' . . . but to what degree?
=C2- In electromagnetic compatibility schools we're taught
=C2- that 'breaks in shields should be kept to 1/10th
=C2- wavelength at frequency of interest to avoid degrading
=C2- that shield's effectiveness'.
=C2- We've seen reflectors for centimeter wave, dish
=C2- antennas made from metallic mesh with significant
=C2- openings . . . yet so small compared to the wavelength
=C2- of the operating frequency as to behave as a solid
=C2- surface.
=C2- When you place a conductor (like a dipole antenna)
=C2- out in the air and exposed it to some EM field,
=C2- then energy at the frequency where the antenna is
=C2- resonant will excite the antenna and manifest with
=C2- a strong current node in the middle and voltage nodes
=C2- at the ends.
=C2- Now, you've got the 1/2 wave piece of wire 'singing'
=C2- in harmony with the constellations of energy that
=C2- are harmonic multiples of the resonant frequency.
=C2- What happens to that energy? If you've got a feeding
=C2- attached at the current node, you can suck of a substantial
=C2- part of that energy and route it someplace else . . . like
=C2- your VOR receiver.
=C2- But unless there is a feed line, energy exciting
=C2- the antenna will be rejected as heat from ohmic
=C2- losses at the current node or re-radiated. After
=C2- all, it HAS to go somewhere.
=C2- So what about those little bits of metal suspended in
=C2- an otherwise non-conductive paint? I suspect that a
=C2- really 'chunky' filling (0.001") flakes would be
=C2- the largest practical filler. What portion of a wavelength
=C2- is 0.001" compared to the wavelength of the comm
=C2- transceiver or even GPS?
=C2- Pretty small. This suggests that the currentsinduced
=C2- in such particles at our frequencies of interest are
=C2- vanishingly small, i.e. insignificant. These particles
=C2- ARE significant at wavelengths of light, hence effective
=C2- modifiers for those electromagnetic fields. However,
=C2- I suspect that there are no measurable effects for such
=C2- particles at our frequencies of interest.
=C2- Particle sizes are simply too far removed from resonancewhere
=C2- significant currents would be induced. No current,
=C2- no heat, no re-radiation, no measurable effects.
=C2- It's an easy experiment to conduct and I have the equipment
=C2- to do it . . . just no time at the moment and I'll need
=C2- to acquire some exemplar coatings to test.
=C2- If anyone is aware of quantified studies conducted on
=C2- this topic, I'd be grateful for some linkage. Anyone
=C2- conversant in an alternative explanation is encouraged
=C2- to correct my mis-conception . . .=C2-
=C2- Bob . . .
Message 10
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| Subject: | Re: Paint question |
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.
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@att.net>
wrote:
> 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@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 . . .
>
>
--
Johnny C.
Message 11
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| Subject: | Re: Paint question |
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?
The Manufacture will ask what color is your plane? And, when you say Candy
Apple Red with Gold Flake.
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@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 . . .
>
> <#m_-6842432749595176325_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>
> Bob . . .
>
Message 12
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| Subject: | Re: Paint question |
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@gmail.com> wrote:
> 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.
>
> 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@att.net>
> wrote:
>
>> 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@a4443518791543424097y_msg_container">
>> <nuckolls.bob@aeroelectric.com>
>> <nuckolls.bob@aeroelectric.com>
>> <nuckolls.bob@aeroelectric.com>
>> <nuckolls.bob@aeroelectric.com>
>>
>> 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 . . . <nuckolls.bob@aeroelectric.com>
>>
>>
>> <https://mail.yahoo.com/neo/launch?.src=ym&reason=myc&soc_src=mail&soc_trk=ma#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>> Bob . . .
>>
>>
>>
>
> --
> Johnny C.
>
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| Subject: | Re: 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:
> 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@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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