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klehman(at)albedo.net
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 Posted: Thu Aug 16, 2007 5:45 am Post subject: strobe whine noise |
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FWIW powering my strobes from separate batteries made no difference to
the audio whine that I was hearing from them. Adding some homemade
filter devices likewise had no effect so I guess I did not hit on the
best component values. I never did find a ground issue that I could
blame the problem on. And yet when I finally obtained and tried a cheap
automotive filter on the 12 volt feed to the strobes, the situation
improved markedly and I can no longer hear the strobes in flight. The
directions said to try reversing the filter leads for best effect. Sure
enough the filter only worked well in one direction. Grounding the
ground connection to the filter also had no effect.
Ken
| Quote: | snip
Bob often recommends powering from a separate battery the piece(s) of
equipment that are involved in the problem. A couple of lantern batteries
could be used to power the radio while the engine is running.. If that
has any effect on the noise, it indicates that the problem is conducted to
the radio via the power bus. Tried that from a separate 12V battery - no effect
snip
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f.miskelly(at)imperial.ac
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| Posted: Thu Aug 16, 2007 7:33 am Post subject: strobe whine noise |
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Hi Ken
How and where did you insert the filter into the 12V feed to the strobes? Sounds like you inserted it 'in line' to the strobes.
Its interesting you inserted the filter before the strobes and yet it reduced the interference in your radio. How do you explain that?
- Frank
________________________________
From: owner-aeroelectric-list-server(at)matronics.com on behalf of Ken
Sent: Thu 16/08/2007 14:45
To: aeroelectric-list(at)matronics.com
Subject: strobe whine noise
FWIW powering my strobes from separate batteries made no difference to
the audio whine that I was hearing from them. Adding some homemade
filter devices likewise had no effect so I guess I did not hit on the
best component values. I never did find a ground issue that I could
blame the problem on. And yet when I finally obtained and tried a cheap
automotive filter on the 12 volt feed to the strobes, the situation
improved markedly and I can no longer hear the strobes in flight. The
directions said to try reversing the filter leads for best effect. Sure
enough the filter only worked well in one direction. Grounding the
ground connection to the filter also had no effect.
Ken
| Quote: | snip
Bob often recommends powering from a separate battery the piece(s) of
equipment that are involved in the problem. A couple of lantern batteries
could be used to power the radio while the engine is running.. If that
has any effect on the noise, it indicates that the problem is conducted to
the radio via the power bus. Tried that from a separate 12V battery - no effect
snip
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mprather(at)spro.net
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| Posted: Thu Aug 16, 2007 8:25 am Post subject: strobe whine noise |
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When tackling a noise problem, it sometimes makes sense to clean up the
victim, but sometimes it also works to clean up the noise source. In this
case, it sounds like the transient current load presented by the strobes
was causing noise to be added to the audio signal of the comm system
(ground/supply noise). Adding a filter to the strobe circuit likely
reduced the transient load on the bus, decreasing the noise signal seen by
the audio system.
Wiring a power supply filter depends on the components in the filter. If
it is just a choke (coil - inductance), in-line works. If it's a 2nd (or
higher) order filter - has a cap, the filter will need to be both inline
and have a connection to ground.
Regards,
Matt-
| Quote: | Hi Ken
How and where did you insert the filter into the 12V feed to the strobes?
Sounds like you inserted it 'in line' to the strobes.
Its interesting you inserted the filter before the strobes and yet it
reduced the interference in your radio. How do you explain that?
- Frank
________________________________
From: owner-aeroelectric-list-server(at)matronics.com on behalf of Ken
Sent: Thu 16/08/2007 14:45
To: aeroelectric-list(at)matronics.com
Subject: strobe whine noise
FWIW powering my strobes from separate batteries made no difference to
the audio whine that I was hearing from them. Adding some homemade
filter devices likewise had no effect so I guess I did not hit on the
best component values. I never did find a ground issue that I could
blame the problem on. And yet when I finally obtained and tried a cheap
automotive filter on the 12 volt feed to the strobes, the situation
improved markedly and I can no longer hear the strobes in flight. The
directions said to try reversing the filter leads for best effect. Sure
enough the filter only worked well in one direction. Grounding the
ground connection to the filter also had no effect.
Ken
>snip
>Bob often recommends powering from a separate battery the piece(s) of
>equipment that are involved in the problem. A couple of lantern
> batteries
>could be used to power the radio while the engine is running.. If that
>has any effect on the noise, it indicates that the problem is conducted
> to
>the radio via the power bus. Tried that from a separate 12V battery - no
> effect
snip
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f.miskelly(at)imperial.ac
Guest
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| Posted: Fri Aug 17, 2007 7:51 am Post subject: strobe whine noise |
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Many thanks for the explanation Matt
- Frank
________________________________
From: owner-aeroelectric-list-server(at)matronics.com on behalf of Matt Prather
Sent: Thu 16/08/2007 17:23
To: aeroelectric-list(at)matronics.com
Subject: RE: strobe whine noise
When tackling a noise problem, it sometimes makes sense to clean up the
victim, but sometimes it also works to clean up the noise source. In this
case, it sounds like the transient current load presented by the strobes
was causing noise to be added to the audio signal of the comm system
(ground/supply noise). Adding a filter to the strobe circuit likely
reduced the transient load on the bus, decreasing the noise signal seen by
the audio system.
Wiring a power supply filter depends on the components in the filter. If
it is just a choke (coil - inductance), in-line works. If it's a 2nd (or
higher) order filter - has a cap, the filter will need to be both inline
and have a connection to ground.
Regards,
Matt-
| Quote: | Hi Ken
How and where did you insert the filter into the 12V feed to the strobes?
Sounds like you inserted it 'in line' to the strobes.
Its interesting you inserted the filter before the strobes and yet it
reduced the interference in your radio. How do you explain that?
- Frank
________________________________
From: owner-aeroelectric-list-server(at)matronics.com on behalf of Ken
Sent: Thu 16/08/2007 14:45
To: aeroelectric-list(at)matronics.com
Subject: strobe whine noise
FWIW powering my strobes from separate batteries made no difference to
the audio whine that I was hearing from them. Adding some homemade
filter devices likewise had no effect so I guess I did not hit on the
best component values. I never did find a ground issue that I could
blame the problem on. And yet when I finally obtained and tried a cheap
automotive filter on the 12 volt feed to the strobes, the situation
improved markedly and I can no longer hear the strobes in flight. The
directions said to try reversing the filter leads for best effect. Sure
enough the filter only worked well in one direction. Grounding the
ground connection to the filter also had no effect.
Ken
>snip
>Bob often recommends powering from a separate battery the piece(s) of
>equipment that are involved in the problem. A couple of lantern
> batteries
>could be used to power the radio while the engine is running.. If that
>has any effect on the noise, it indicates that the problem is conducted
> to
>the radio via the power bus. Tried that from a separate 12V battery - no
> effect
snip
|
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klehman(at)albedo.net
Guest
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| Posted: Sat Aug 18, 2007 4:54 am Post subject: strobe whine noise |
|
|
Hi Frank
Yes the filter is in line with the strobe power after the power switch.
My best theory is similar to Matt's and that the noise is coming in via
the common grounds. It is a metal airframe and the strobe power
supplies are internally grounded to their metal cases, same as the
radio and the intercom. The headphone jacks are isolated from ground.
Everything except the strobes has a ground wire to the forrest of tabs
on the firewall. Since the ground connection on the filter has no
effect, it seems to me that it can't be a capacitor in the filter that
is helping. And yet reversing the filter leads does make a difference
which seems an unlikely result to me. I don't think there can be
anything else other than a choke (inductor) in the filter??
If I was still building I think I would try electrically insulating the
strobe power supplies from the airframe with plastic washers and bolts.
I seem to recall opening the aeroflash units when I installed them but I
must have decided that their grounds could not be easilly separated from
the case, or it did not seem worth the effort at the time. The strobe
heads are mounted in fibreglass wingtips so they should already be
isolated from the airframe.
Ken
Matt Prather wrote:
| Quote: |
When tackling a noise problem, it sometimes makes sense to clean up the
victim, but sometimes it also works to clean up the noise source. In this
case, it sounds like the transient current load presented by the strobes
was causing noise to be added to the audio signal of the comm system
(ground/supply noise). Adding a filter to the strobe circuit likely
reduced the transient load on the bus, decreasing the noise signal seen by
the audio system.
Wiring a power supply filter depends on the components in the filter. If
it is just a choke (coil - inductance), in-line works. If it's a 2nd (or
higher) order filter - has a cap, the filter will need to be both inline
and have a connection to ground.
Regards,
Matt-
>Hi Ken
>
>How and where did you insert the filter into the 12V feed to the strobes?
>Sounds like you inserted it 'in line' to the strobes.
>
>Its interesting you inserted the filter before the strobes and yet it
>reduced the interference in your radio. How do you explain that?
>
> - Frank
>
>________________________________
>
>From: owner-aeroelectric-list-server(at)matronics.com on behalf of Ken
>Sent: Thu 16/08/2007 14:45
>To: aeroelectric-list(at)matronics.com
>Subject: strobe whine noise
>
>
>
>FWIW powering my strobes from separate batteries made no difference to
>the audio whine that I was hearing from them. Adding some homemade
>filter devices likewise had no effect so I guess I did not hit on the
>best component values. I never did find a ground issue that I could
>blame the problem on. And yet when I finally obtained and tried a cheap
>automotive filter on the 12 volt feed to the strobes, the situation
>improved markedly and I can no longer hear the strobes in flight. The
>directions said to try reversing the filter leads for best effect. Sure
>enough the filter only worked well in one direction. Grounding the
>ground connection to the filter also had no effect.
>Ken
>
>
>
>>snip
>>Bob often recommends powering from a separate battery the piece(s) of
>>equipment that are involved in the problem. A couple of lantern
>>batteries
>>could be used to power the radio while the engine is running.. If that
>>has any effect on the noise, it indicates that the problem is conducted
>>to
>>the radio via the power bus. Tried that from a separate 12V battery - no
>>effect
>>
>>
>>
>>
>snip
>
>
|
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nuckollsr(at)cox.net
Guest
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| Posted: Sat Aug 18, 2007 9:32 pm Post subject: strobe whine noise |
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|
At 08:53 AM 8/18/2007 -0400, you wrote:
| Quote: |
Hi Frank
Yes the filter is in line with the strobe power after the power switch.
My best theory is similar to Matt's and that the noise is coming in via
the common grounds. It is a metal airframe and the strobe power supplies
are internally grounded to their metal cases, same as the radio and the
intercom. The headphone jacks are isolated from ground. Everything except
the strobes has a ground wire to the forrest of tabs on the firewall.
Since the ground connection on the filter has no effect, it seems to me
that it can't be a capacitor in the filter that is helping. And yet
reversing the filter leads does make a difference which seems an unlikely
result to me. I don't think there can be anything else other than a choke
(inductor) in the filter??
If I was still building I think I would try electrically insulating the
strobe power supplies from the airframe with plastic washers and bolts. I
seem to recall opening the aeroflash units when I installed them but I
must have decided that their grounds could not be easilly separated from
the case, or it did not seem worth the effort at the time. The strobe
heads are mounted in fibreglass wingtips so they should already be
isolated from the airframe.
|
Hmmmm . . . grounds contribute to noise issues ONLY when
sensitive potential victims share TWO or more ground
paths. If you have immediate access to the power supplies,
try the dry-battery experiment again with the battery located
right at the power supply and grounded locally to the power
supply.
There's something we're not seeing here. I presume that your
power supply does ground locally and doesn't have a second wire
running all the way to the firewall ground bus????
Bob . . .
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f.miskelly(at)imperial.ac
Guest
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| Posted: Sun Aug 19, 2007 11:28 am Post subject: strobe whine noise |
|
|
Thanks Ken and Bob. I'll try Bob's suggestion of connecting both +ve and -ve of the battery to the radio later this week
Bob - my radio has a +ve from the power bus and a -ve which grounds at the firewall ground bus. I suspect it also grounds locally
- Frank
________________________________
From: owner-aeroelectric-list-server(at)matronics.com on behalf of Robert L. Nuckolls, III
Sent: Sun 19/08/2007 07:33
To: aeroelectric-list(at)matronics.com
Subject: Re: strobe whine noise
At 08:53 AM 8/18/2007 -0400, you wrote:
| Quote: |
Hi Frank
Yes the filter is in line with the strobe power after the power switch.
My best theory is similar to Matt's and that the noise is coming in via
the common grounds. It is a metal airframe and the strobe power supplies
are internally grounded to their metal cases, same as the radio and the
intercom. The headphone jacks are isolated from ground. Everything except
the strobes has a ground wire to the forrest of tabs on the firewall.
Since the ground connection on the filter has no effect, it seems to me
that it can't be a capacitor in the filter that is helping. And yet
reversing the filter leads does make a difference which seems an unlikely
result to me. I don't think there can be anything else other than a choke
(inductor) in the filter??
If I was still building I think I would try electrically insulating the
strobe power supplies from the airframe with plastic washers and bolts. I
seem to recall opening the aeroflash units when I installed them but I
must have decided that their grounds could not be easilly separated from
the case, or it did not seem worth the effort at the time. The strobe
heads are mounted in fibreglass wingtips so they should already be
isolated from the airframe.
|
Hmmmm . . . grounds contribute to noise issues ONLY when
sensitive potential victims share TWO or more ground
paths. If you have immediate access to the power supplies,
try the dry-battery experiment again with the battery located
right at the power supply and grounded locally to the power
supply.
There's something we're not seeing here. I presume that your
power supply does ground locally and doesn't have a second wire
running all the way to the firewall ground bus????
Bob . . .
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nuckollsr(at)cox.net
Guest
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| Posted: Sun Aug 19, 2007 12:53 pm Post subject: strobe whine noise |
|
|
At 08:23 PM 8/19/2007 +0100, you wrote:
| Quote: | Thanks Ken and Bob. I'll try Bob's suggestion of connecting both +ve and
-ve of the battery to the radio later this week
Bob - my radio has a +ve from the power bus and a -ve which grounds at the
firewall ground bus. I suspect it also grounds locally
|
my suggested experiment was to power the strobe locally and
leave it grounded . . . but your assertion raises another
possibility. If the radio has an internal ground to chassis,
then try simply removing the 'extra' ground to the firewall.
You may be experiencing a rare but real situation that was
addressed with the last upgrade to Z-15 in particular where
the idea of an avionics ground ON THE PANEL was suggested
for gathering all grounds for panel mounted devices together
at a single point before extending the ground to the firewall.
In fact, in the all metal airplane, the panel ground could
be tied to the panel as an airframe ground . . . the extra
wires to the firewall would not be beneficial. However,
Getting all the panel grounds tied together on or near where
the radios bring their internal grounds is a good thing to
consider. MOST of the time, it's not an issue . . . which goes
for the vast majority of installations in light aircraft since
day-one. From time to time, situations like yours do arise
where the standard cures for filtering and shielding have
no effect and sometimes make it worse.
When you finally discover the root cause of your noise
it will be stone simple and probably have nothing to do
with shielding or filtering.
Bob . . .
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