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nuckolls.bob(at)aeroelect
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 Posted: Thu Feb 16, 2012 7:37 pm Post subject: Speaking of EMC filters |
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I have received a couple of HID lamp kits for
evaluation with respect to EMC characteristics
in OBAM aircraft.
The first thing I did was order some HID conversions
for the high beams on my Sedona. Noises from these
lights are readily detectable while tuning around
on the AM radio.
The kit ballasts appear to have some sort of filter
in the harness between the ballast and lamp. However,
there is no such filter in the power input lead.
I've been side-tracked on a task for a customer but
I think I can get back on the bench next week. I'll
light one of these kits up on the bench and then
tune around with my DC-to-Light receiver. I can
get a rough idea of the fundamental excitation
frequency.
I'll take a whack at some filtering on the DC
input leads which goes to conducted noise. However,
if there is significant radiation from the output
leads and/or lamp, the problem is significantly
different.
I just learned today that I may be joining with NIAR
at WSU on some interesting endeavors. The folks I
used to work with at HBC in the EMC/EMI business
now work at NIAR with all new facilities and gear.
If the problem proves intractable using shade-tree
techniques, maybe I can get into the screen room and
secure a quick look-see with spectrum analyzer and probes.
Bob . . .
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nuckolls.bob(at)aeroelect
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| Posted: Sat Feb 18, 2012 10:06 am Post subject: Speaking of EMC filters |
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At 09:34 PM 2/16/2012, you wrote:
<nuckolls.bob(at)aeroelectric.com>
I have received a couple of HID lamp kits for
evaluation with respect to EMC characteristics
in OBAM aircraft.
The first thing I did was order some HID conversions
for the high beams on my Sedona. Noises from these
lights are readily detectable while tuning around
on the AM radio.
The kit ballasts appear to have some sort of filter
in the harness between the ballast and lamp. However,
there is no such filter in the power input lead.
I've been side-tracked on a task for a customer but
I think I can get back on the bench next week. I'll
light one of these kits up on the bench and then
tune around with my DC-to-Light receiver. I can
get a rough idea of the fundamental excitation
frequency.
Saturday:
I did get a chance to fire up one of the HID
kits supplied for EMC evaluation.
On the bench, the light/ballast combination
produced very little noise in the killohertz
ranges (ADF, AM broadcast). Further, I could
not identify a fundamental frequency of
operation for the ballast in the short time
I was "searching". No doubt there is one
but it will take more diligence to identify.
What I did notice was that the system was a significant
BROADBAND noise source in the 100 MHz ranges.
This is not good. Broadband sources are generally
not electronic . . . they tend to be the result
of more chaotic behaviors like gazillions of
super-hot molecules crashing around in a
'glow tube'.
There is what appears to be an in-line filter
on the lead wires between ballast and lamp.
Given that it has to operate at voltage levels
in the thousands of volts, this is no trival
design job. Further, while one might THINK
that this filter is supplied to mitigate noise
from ballast electronics, it may well be that
its primary purpose is to reduce propagation
of noise from the lamp itself.
I've got to bug out for Wichita but I'll
be thinking about the next step for quantifying/
qualifying the problem.
Bob . . .
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dave.saylor.aircrafters(a
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| Posted: Sat Feb 18, 2012 12:36 pm Post subject: Speaking of EMC filters |
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I have one of the lamps you're evaluating in each wing tip. One tip has an Archer comm antenna (for comm 2) and one has an Archer nav antenna. I hear a big FZZZZT from comm 2 every time the lamp flashes, or continuously if it's on steady. It seems constant throughout the frequency range. The nav flags if the signal isn't very strong. I haven't experimented with it enough to say any more than if I turn off the HID, the signal comes in and vice versa.
I sure appreciate your help, Bob. Can't wait to hear what you find.
Dave Saylor
AirCrafters
140 Aviation Way
Watsonville, CA 95076
831-722-9141 Shop
831-750-0284 Cell
On Sat, Feb 18, 2012 at 10:00 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
[quote] --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>
At 09:34 PM 2/16/2012, you wrote:
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>
I have received a couple of HID lamp kits for
evaluation with respect to EMC characteristics
in OBAM aircraft.
The first thing I did was order some HID conversions
for the high beams on my Sedona. Noises from these
lights are readily detectable while tuning around
on the AM radio.
The kit ballasts appear to have some sort of filter
in the harness between the ballast and lamp. However,
there is no such filter in the power input lead.
I've been side-tracked on a task for a customer but
I think I can get back on the bench next week. I'll
light one of these kits up on the bench and then
tune around with my DC-to-Light receiver. I can
get a rough idea of the fundamental excitation
frequency.
 Saturday:
 I did get a chance to fire up one of the HID
 kits supplied for EMC evaluation.
 On the bench, the light/ballast combination
 produced very little noise in the killohertz
 ranges (ADF, AM broadcast). Further, I could
 not identify a fundamental frequency of
 operation for the ballast in the short time
 I was "searching". No doubt there is one
 but it will take more diligence to identify.
 What I did notice was that the system was a significant
 BROADBAND noise source in the 100 MHz ranges.
 This is not good. Broadband sources are generally
 not electronic . . . they tend to be the result
 of more chaotic behaviors like gazillions of
 super-hot molecules crashing around in a
 'glow tube'.
 There is what appears to be an in-line filter
 on the lead wires between ballast and lamp.
 Given that it has to operate at voltage levels
 in the thousands of volts, this is no trival
 design job. Further, while one might THINK
 that this filter is supplied to mitigate noise
 from ballast electronics, it may well be that
 its primary purpose is to reduce propagation
 of noise from the lamp itself.
 I've got to bug out for Wichita but I'll
 be thinking about the next step for quantifying/
 qualifying the problem.
 Bob . . .
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[b]
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nuckolls.bob(at)aeroelect
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| Posted: Sat Feb 18, 2012 1:00 pm Post subject: Speaking of EMC filters |
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At 02:33 PM 2/18/2012, you wrote:
| Quote: | I have one of the lamps you're evaluating in
each wing tip. One tip has an Archer comm
antenna (for comm 2) and one has an Archer nav
antenna. I hear a big FZZZZT from comm 2 every
time the lamp flashes, or continuously if it's
on steady. It seems constant throughout the
frequency range. The nav flags if the signal
isn't very strong. I haven't experimented with
it enough to say any more than if I turn off the
HID, the signal comes in and vice versa.
I sure appreciate your help, Bob. Can't wait to hear what you find.
|
Your findings are consistent with the theory
broad-band noise from the lamp's high energy
agitation of electrons on gas atoms.
Antenna proximity is going to be the elephant
in the room. I set my hand-held on one end of
a 7' bench from my signal generator which I
set up to produce an audible but noisy, modulated
signal. This would be roughly analogous to listening
to a weak station that is just above un-servicable.
I was carrying the HID around on a portable battery.
If I were 6' or more away from the hand held, I
could barely detect any influence of the HID
lamp on received signal.
From 3' away, the extra noise offered by the HID
lamp would have rendered the "remote station"
useless. Needless to say, an overwhelming
noise at those signal levels is not very
big. Indeed, probably insignificant to FM
radio reception in vehicles. I'll get some better
sense of the size of the problem when I get back
to M.L. on Monday.
In the mean time, can you hear the noise from a
hand held in the cockpit? Tune to open channel
and open the squelch. Turn the lamp on/off and
see if you can hear any change in the receiver's
normal background noise. Wearing headphones will
help.
Bob . . .
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dave.saylor.aircrafters(a
Guest
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| Posted: Sat Feb 18, 2012 1:13 pm Post subject: Speaking of EMC filters |
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I'll check with a handheld on Monday.
--Dave Saylor
[quote] Â In the mean time, can you hear the noise from a
 hand held in the cockpit?
[b]
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dave.saylor.aircrafters(a
Guest
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| Posted: Thu Feb 23, 2012 9:33 am Post subject: Speaking of EMC filters |
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| Quote: | Â In the mean time, can you hear the noise from a
 hand held in the cockpit? Tune to open channel
 and open the squelch. Turn the lamp on/off and
 see if you can hear any change in the receiver's
 normal background noise. Wearing headphones will
 help.
|
I can't hear the noise in the cockpit. I hear a very faint static
related to the lamps but not the objectionable loud noise I hear in
(the Archer antenna-ed) comm 2.
The slight noise seems constant until I move from the cockpit to
within about six feet of the lamp. Then it seems to increase a bit
with proximity but even close to the antenna it's not very loud.
However, if I put the handheld within a foot of the lamp, it breaks
squelch and makes the loud noise I'm trying to limit. With the
wig-wag on, the noise correlates perfectly to the lamp. It's
interesting, you can almost visualize the shape of the objectionable
area. The Archer antenna is within this noisy volume but it's size
requires the proximity.
If I leave the antenna in the wingtip, it has to be close to the lamp.
With some effort I could move the antenna. What are my options for
blocking the emissions? If I succeeded could I expect any remaining
antenna performance?
On a side note, the right lamp worked intermittently on the last
flight. Now it seems completely dead.
Dave Saylor
AirCrafters
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Thu Feb 23, 2012 12:07 pm Post subject: Speaking of EMC filters |
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| Quote: | I can't hear the noise in the cockpit. I hear a very faint static
related to the lamps but not the objectionable loud noise I hear in
(the Archer antenna-ed) comm 2.
The slight noise seems constant until I move from the cockpit to
within about six feet of the lamp. Then it seems to increase a bit
with proximity but even close to the antenna it's not very loud.
|
<snip>
| Quote: | If I leave the antenna in the wingtip, it has to be close to the lamp.
With some effort I could move the antenna. What are my options for
blocking the emissions? If I succeeded could I expect any remaining
antenna performance?
|
Hmmmm . . . no way to "block" without shielding
the lamp assembly. Doing this without diminishing
the value as a lamp is hard. Waayyyy back when
I was a Cessna when one of the strobe guys (I think
it was Whelen) sent us some hardware to play with.
Motor driven "light houses" under red domes were
the collision avoidance technology of choice.
The tubes emitted broadband noise heard as a 'pop'
in the radio. I remember Gordon Wood considering
some fine wire mesh to form a shield around the
flash tube assembly but 95% open to allow light
to pass.
I think they finally decided that the noise was
too small to be worried about . . . although
I've flown some rentals where the 'pop' was
definitely annoying.
Your story correlates with my experiments here.
I'm pretty sure it's radiation directly from the
gas filled tube. It may well be that your Archer
antenna is simply too close
| Quote: | On a side note, the right lamp worked intermittently on the last
flight. Now it seems completely dead.
|
Hopefully an isolated case. I'll scratch
around the 'net on HID EMC issues. I'll see
if anyone out at HBC has been looking into
it too. Doubtful. That once great airplane
company is sitting in the middle of the pond
on melting ice.
Bob . . .
| Quote: | Dave Saylor
AirCrafters
-----
No virus found in this message.
Checked by AVG - www.avg.com
|
Bob . . .
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