A aviation & planes forum. AviationBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AviationBanter forum » rec.aviation newsgroups » Owning
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Noise Problem. Both Comms Breaking Squelch



 
 
Thread Tools Display Modes
  #1  
Old March 27th 08, 11:27 PM posted to rec.aviation.owning
Lancair IV-P Flyer
external usenet poster
 
Posts: 9
Default Noise Problem. Both Comms Breaking Squelch

Would anyone have an idea about the cause of this?

Problem:
Intermittent noise (sounds just like a squelch volume test) on both
communication radios. Lasts from 15 seconds to two minutes. Will
occur at any RPM including idle. Changing frequencies eliminates the
noise but the noise can and most likely will come back shortly on that
same frequency.

I have a back up alternator on this aircraft and when I have the main
alternator turned off to check the operation of the backup alternator,
the noise never seems to occur. Also, when the noise manifests, if I
turn off the alternator the noise always goes away. I have done this
several times on the ground and it has been 100%. The voltage
regulator has just been replaced and the noise is still present. The
alternator has been rebuilt three times in the last 30 hours of
operation. The alternator shop is tired of hearing from me. This
squelch break noise is new however in the last 15 hours of
operation.

The alternator has been having so much trouble because we have been
trying to locate an alternator field circuit breaker popping issue.
Typical scenario is the aircraft must fly for at least 40 minutes
before the breaker will pop. Usually, it pops in conjunction with a
small static crack in the headset and a voltage excursion of one to
two volts. This most often happens in level flight. This same
voltage excursion has been noted at least once when the main
alternator is turned off and running on the backup alternator.

All connections in the alternator/breaker/battery/ground circuit have
been cleaned, tightened and cable ends replaced when suspect. All to
no avail. This is a 24 volt single battery system. Running the 35
amp hydraulic pump to actuate flaps or gear will on occasion trigger a
field alternator breaker pop but many times it won't either.

Thanks in advance for any light you might be able to shine on this
problem.
  #2  
Old March 28th 08, 02:26 PM posted to rec.aviation.owning
Nathan Young
external usenet poster
 
Posts: 108
Default Noise Problem. Both Comms Breaking Squelch

On Thu, 27 Mar 2008 15:27:52 -0700 (PDT), Lancair IV-P Flyer
wrote:

Would anyone have an idea about the cause of this?



Two ideas to check:

#1. Use a battery powered handheld radio to see if it breaks squelch
as well. This will tell you if the noise is RF based or coupled into
the DC power within the plane.

#2. Have you replaced the field circuit breaker? I don't know how it
would cause the squelch issue, but a bad breaker might contribute to
some of the odd electrical system issues you are experiencing.

I had a bad field breaker that worked about 99% of the time, but would
occasionally exhibit a resistance, which caused a voltage drop across
the breaker, which caused the voltage regulator to crank up the
voltage. After hitting turbulence, the breaker would jostle just
enough to lose the resistance, and then the over voltage regulator
would trip, and take the alternator off line. I went through 2
alternators, a VR, and an OVR before I decided to debug this problem
myself and eventually found the bad circuit breaker.

-Nathan

  #3  
Old March 28th 08, 04:30 PM posted to rec.aviation.owning
Lancair IV-P Flyer
external usenet poster
 
Posts: 9
Default Noise Problem. Both Comms Breaking Squelch

On Mar 28, 5:26 am, Nathan Young wrote:
On Thu, 27 Mar 2008 15:27:52 -0700 (PDT), Lancair IV-P Flyer

wrote:
Would anyone have an idea about the cause of this?


Two ideas to check:

#1. Use a battery powered handheld radio to see if it breaks squelch
as well. This will tell you if the noise is RF based or coupled into
the DC power within the plane.

#2. Have you replaced the field circuit breaker? I don't know how it
would cause the squelch issue, but a bad breaker might contribute to
some of the odd electrical system issues you are experiencing.

I had a bad field breaker that worked about 99% of the time, but would
occasionally exhibit a resistance, which caused a voltage drop across
the breaker, which caused the voltage regulator to crank up the
voltage. After hitting turbulence, the breaker would jostle just
enough to lose the resistance, and then the over voltage regulator
would trip, and take the alternator off line. I went through 2
alternators, a VR, and an OVR before I decided to debug this problem
myself and eventually found the bad circuit breaker.

-Nathan


Nathan,

Thanks for the ideas. I will try the hand held radio test. I have
already replaced the field circuit breaker. There was no change in
the symptoms so I don't think that made a difference. I am wondering
if the breaking squelch is unrelated to voltage excursions and breaker
tripping events. Since I can usually get the squelch to break on the
ground, I am thinking of pulling breakers one at a time while the
squelch break event is in progress to see if there is an instrument
that may be causing that noise.

Thanks again,
Steve
  #4  
Old March 28th 08, 08:03 PM posted to rec.aviation.owning
Lancair IV-P Flyer
external usenet poster
 
Posts: 9
Default Noise Problem. Both Comms Breaking Squelch

On Mar 28, 8:30 am, Lancair IV-P Flyer wrote:
On Mar 28, 5:26 am, Nathan Young wrote:



On Thu, 27 Mar 2008 15:27:52 -0700 (PDT), Lancair IV-P Flyer


wrote:
Would anyone have an idea about the cause of this?


Two ideas to check:


#1. Use a battery powered handheld radio to see if it breaks squelch
as well. This will tell you if the noise is RF based or coupled into
the DC power within the plane.


#2. Have you replaced the field circuit breaker? I don't know how it
would cause the squelch issue, but a bad breaker might contribute to
some of the odd electrical system issues you are experiencing.


I had a bad field breaker that worked about 99% of the time, but would
occasionally exhibit a resistance, which caused a voltage drop across
the breaker, which caused the voltage regulator to crank up the
voltage. After hitting turbulence, the breaker would jostle just
enough to lose the resistance, and then the over voltage regulator
would trip, and take the alternator off line. I went through 2
alternators, a VR, and an OVR before I decided to debug this problem
myself and eventually found the bad circuit breaker.


-Nathan


Nathan,

Thanks for the ideas. I will try the hand held radio test. I have
already replaced the field circuit breaker. There was no change in
the symptoms so I don't think that made a difference. I am wondering
if the breaking squelch is unrelated to voltage excursions and breaker
tripping events. Since I can usually get the squelch to break on the
ground, I am thinking of pulling breakers one at a time while the
squelch break event is in progress to see if there is an instrument
that may be causing that noise.

Thanks again,
Steve


The handheld radio had no static. However, it gave me an idea to
power up the radios without the engine running to isolate whether it
is alternator based. I can get the static without the engine
running. The alternator switch is off so the VR is not powered up
either so the static is coming from a powered instrument it would
seem. So, why does the static go away when the engine is running and
the alternator switch is turned off?

Steve
  #5  
Old March 29th 08, 01:45 PM posted to rec.aviation.owning
[email protected]
external usenet poster
 
Posts: 6
Default Noise Problem. Both Comms Breaking Squelch

On Mar 27, 5:27*pm, Lancair IV-P Flyer wrote:
Would anyone have an idea about the cause of this?

Problem:
Intermittent noise (sounds just like a squelch volume test) on both
communication radios. *Lasts from 15 seconds to two minutes. *Will
occur at any RPM including idle. *Changing frequencies eliminates the
noise but the noise can and most likely will come back shortly on that
same frequency.

I have a back up alternator on this aircraft and when I have the main
alternator turned off to check the operation of the backup alternator,
the noise never seems to occur. *Also, when the noise manifests, if I
turn off the alternator the noise always goes away. *I have done this
several times on the ground and it has been 100%. *The voltage
regulator has just been replaced and the noise is still present. *The
alternator has been rebuilt three times in the last 30 hours of
operation. *The alternator shop is tired of hearing from me. *This
squelch break noise is new however in the last 15 hours of
operation.

The alternator has been having so much trouble because we have been
trying to locate an alternator field circuit breaker popping issue.
Typical scenario is the aircraft must fly for at least 40 minutes
before the breaker will pop. *Usually, it pops in conjunction with a
small static crack in the headset and a voltage excursion of one to
two volts. *This most often happens in level flight. *This same
voltage excursion has been noted at least once when the main
alternator is turned off and running on the backup alternator.

All connections in the alternator/breaker/battery/ground circuit have
been cleaned, tightened and cable ends replaced when suspect. *All to
no avail. *This is a 24 volt single battery system. *Running the 35
amp hydraulic pump to actuate flaps or gear will on occasion trigger a
field alternator breaker pop but many times it won't either.

Thanks in advance for any light you might be able to shine on this
problem.


I had a similar thing happen with one of my Vikings once. I took it
over to a freind at CRP who owns an avionics shop. He put an
oscilloscole on my 12 volt bus and found an ac sine wave. Easy fix!
Repair the alternator. An alternator is an ac device. there is a diode
trio (set of 3 diodes) that rectify the ac to dc. If a diode goes bad
it will still provide voltage but will have an ac componant and noise.
An easy way to test it is to pull the alt field circuit breaker. If
this is your problem, you owe me a ride.

Dewey
  #6  
Old March 29th 08, 03:58 PM posted to rec.aviation.owning
Lancair IV-P Flyer
external usenet poster
 
Posts: 9
Default Noise Problem. Both Comms Breaking Squelch

On Mar 29, 4:45 am, "
wrote:
On Mar 27, 5:27 pm, Lancair IV-P Flyer wrote:



Would anyone have an idea about the cause of this?


Problem:
Intermittent noise (sounds just like a squelch volume test) on both
communication radios. Lasts from 15 seconds to two minutes. Will
occur at any RPM including idle. Changing frequencies eliminates the
noise but the noise can and most likely will come back shortly on that
same frequency.


I have a back up alternator on this aircraft and when I have the main
alternator turned off to check the operation of the backup alternator,
the noise never seems to occur. Also, when the noise manifests, if I
turn off the alternator the noise always goes away. I have done this
several times on the ground and it has been 100%. The voltage
regulator has just been replaced and the noise is still present. The
alternator has been rebuilt three times in the last 30 hours of
operation. The alternator shop is tired of hearing from me. This
squelch break noise is new however in the last 15 hours of
operation.


The alternator has been having so much trouble because we have been
trying to locate an alternator field circuit breaker popping issue.
Typical scenario is the aircraft must fly for at least 40 minutes
before the breaker will pop. Usually, it pops in conjunction with a
small static crack in the headset and a voltage excursion of one to
two volts. This most often happens in level flight. This same
voltage excursion has been noted at least once when the main
alternator is turned off and running on the backup alternator.


All connections in the alternator/breaker/battery/ground circuit have
been cleaned, tightened and cable ends replaced when suspect. All to
no avail. This is a 24 volt single battery system. Running the 35
amp hydraulic pump to actuate flaps or gear will on occasion trigger a
field alternator breaker pop but many times it won't either.


Thanks in advance for any light you might be able to shine on this
problem.


I had a similar thing happen with one of my Vikings once. I took it
over to a freind at CRP who owns an avionics shop. He put an
oscilloscole on my 12 volt bus and found an ac sine wave. Easy fix!
Repair the alternator. An alternator is an ac device. there is a diode
trio (set of 3 diodes) that rectify the ac to dc. If a diode goes bad
it will still provide voltage but will have an ac componant and noise.
An easy way to test it is to pull the alt field circuit breaker. If
this is your problem, you owe me a ride.

Dewey


Dewey,

Thanks for your suggestion on the alternator. My only problem is I
can make the noise appear when the engine is not running (only battery
voltage). When the engine is running and the alternator is online, I
can get the noise to stop by turning off the alternator switch. So, I
thought the alternator was it until I did the test without the engine
running.

Thanks,
Steve
  #7  
Old March 29th 08, 04:57 PM posted to rec.aviation.owning
Nathan Young
external usenet poster
 
Posts: 108
Default Noise Problem. Both Comms Breaking Squelch

On Fri, 28 Mar 2008 12:03:30 -0700 (PDT), Lancair IV-P Flyer
wrote:


The handheld radio had no static. However, it gave me an idea to
power up the radios without the engine running to isolate whether it
is alternator based. I can get the static without the engine
running. The alternator switch is off so the VR is not powered up
either so the static is coming from a powered instrument it would
seem. So, why does the static go away when the engine is running and
the alternator switch is turned off?


Hmmm. It is odd that the shutting off the alternator field current
seems to fix the static, but meanwhile you also get the static while
on the ground without the engine running.

I think your idea to pull breakers while on the ground without the
engine running is a good next step.

You mentioned a voltmeter in the plane. Does it oscillate or is it
fairly stable? I don't know if you have access to one, but it would
be really helpful to see an oscilloscope on the main bus when the
static condition occurs.

BTW - where are you based?

  #8  
Old March 29th 08, 09:43 PM posted to rec.aviation.owning
Lancair IV-P Flyer
external usenet poster
 
Posts: 9
Default Noise Problem. Both Comms Breaking Squelch

On Mar 29, 7:57 am, Nathan Young wrote:
On Fri, 28 Mar 2008 12:03:30 -0700 (PDT), Lancair IV-P Flyer

wrote:

The handheld radio had no static. However, it gave me an idea to
power up the radios without the engine running to isolate whether it
is alternator based. I can get the static without the engine
running. The alternator switch is off so the VR is not powered up
either so the static is coming from a powered instrument it would
seem. So, why does the static go away when the engine is running and
the alternator switch is turned off?


Hmmm. It is odd that the shutting off the alternator field current
seems to fix the static, but meanwhile you also get the static while
on the ground without the engine running.

I think your idea to pull breakers while on the ground without the
engine running is a good next step.

You mentioned a voltmeter in the plane. Does it oscillate or is it
fairly stable? I don't know if you have access to one, but it would
be really helpful to see an oscilloscope on the main bus when the
static condition occurs.

BTW - where are you based?


Nathan,

I have two voltmeters on board. They both show very steady voltage
within 0.1 volt except when there is a voltage excursion which occurs
at least 40 minutes into a flight. The voltage excursions are usually
less than two volts but sometimes there is enough of a spike to trip
the alternator field circuit breaker. I replaced the circuit breaker
but no change in the problem. I now have a new voltage regulator but
have not flown the plane yet to see if that made a difference. I have
a couple of trips planned for this week and will get a good look at
things with the new VR.

The oscilloscope idea is a good one. I will have to see if I can find
access to one.

I am based at LWS (Lewiston, Idaho on the Lewis and Clark trail).

Steve
  #9  
Old April 1st 08, 02:59 AM posted to rec.aviation.owning
MikeMl
external usenet poster
 
Posts: 33
Default Noise Problem. Both Comms Breaking Squelch

Lancair IV-P Flyer wrote:
On Mar 29, 4:45 am, "

Steve,

I do not have any specific Lancair experience, however, I know about
Cessnas. The new glass-panel Cessnas have an alternator controller which
includes an overvoltage detector which incorporates an electronic
"crowbar" circuit. It purposely overloads and trips the Alternator Field
Breaker if a momentary bus voltage transient is detected. Could your
Lancair have a similar system?

On the radios unsquelching, is it possible that the radios are just
overly voltage sensitive? With the alternator on-line, the bus voltage
should be nominally 28.5V. With the alternator off-line, the bus voltage
will quickly sag to about 24V. Some radios do better than others at not
having their squelch threshold change when the input power changes that
much.

MikeM
  #10  
Old April 1st 08, 05:00 AM posted to rec.aviation.owning
Lancair IV-P Flyer
external usenet poster
 
Posts: 9
Default Noise Problem. Both Comms Breaking Squelch

On Mar 31, 5:59 pm, MikeMl wrote:
Lancair IV-P Flyer wrote:
On Mar 29, 4:45 am, "


Steve,

I do not have any specific Lancair experience, however, I know about
Cessnas. The new glass-panel Cessnas have an alternator controller which
includes an overvoltage detector which incorporates an electronic
"crowbar" circuit. It purposely overloads and trips the Alternator Field
Breaker if a momentary bus voltage transient is detected. Could your
Lancair have a similar system?

On the radios unsquelching, is it possible that the radios are just
overly voltage sensitive? With the alternator on-line, the bus voltage
should be nominally 28.5V. With the alternator off-line, the bus voltage
will quickly sag to about 24V. Some radios do better than others at not
having their squelch threshold change when the input power changes that
much.

MikeM


Mike,

The solid state voltage regulators used in many experimental category
aircraft do in fact have "crowbar" type protection as well as over
voltage protection. As I understand the operation of the crowbar trip
from a simple over voltage trip is if the crowbar opens the circuit,
it can only be reset by turning off the alternator switch. Once that
occurs, you can reset the breaker, turn the alternator switch back on
and the alternator will be back in business. My breaker trips are
always resettable without resetting requirement of the alternator
switch. So, I think something is shorting to ground that shouldn't
be. I am thinking the main alternator may still be the culprit or
possibly the battery, which is an AGM type, may be shorting as it
heats up. I am going to try pulling the field breaker and sense
breaker of the backup alternator to see if the problems occur during
the isolation. If so, then running from the backup system and pulling
the breakers of the main system. If the failures only occur on the
main system I am going to replace the alternator with a completely
different unit. If both tests show voltage excursions, I am going to
replace the battery and see if that isn't the culprit. There is
really not much left to try.

Thanks for your help.
Steve
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Tough noise problem in Arrow radios Ray Andraka Owning 7 February 18th 08 09:44 PM
FAA paper Noise Attenuation Properties of Noise-Canceling Headsets Jim Macklin Piloting 26 January 13th 07 01:06 AM
FAA paper Noise Attenuation Properties of Noise-Canceling Headsets Jim Macklin Instrument Flight Rules 15 January 13th 07 01:06 AM
Static/Squelch Noise in Radio Kensandyeggo Home Built 2 April 13th 06 09:00 PM
Radio "Squelch-type" Noise Kensandyeggo Owning 7 April 12th 06 07:20 PM


All times are GMT +1. The time now is 04:25 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AviationBanter.
The comments are property of their posters.