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. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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 | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Tough noise problem in Arrow radios | Ray Andraka | Owning | 7 | February 18th 08 08:44 PM |
FAA paper Noise Attenuation Properties of Noise-Canceling Headsets | Jim Macklin | Piloting | 26 | January 13th 07 12:06 AM |
FAA paper Noise Attenuation Properties of Noise-Canceling Headsets | Jim Macklin | Instrument Flight Rules | 15 | January 13th 07 12:06 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 |