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nuckolls.bob(at)aeroelect
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 Posted: Sun Aug 30, 2015 7:39 am Post subject: Request for some direction and advise |
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At 03:17 PM 8/29/2015, you wrote:
Bob,
I apologize for writing you directly but I am at my wits end with this problem.
Not a problem except that we should do this
on the List . . . there are individuals who
are able and willing to contribute to the
study/solution, many more who would benefit
from reading the exchanges . . ..
First let me tell you that I have a GNS430W and a TruTrack Digiflight II VSVG autopilot along with the Dynon 10A and Dynon HS34 module to connect the Dynon to the GNS430W.
I have always had a problem with the radio developing a lot of static on certain frequencies to the extent that I could not make out what was being said. Not always, but mostly I would get this very loud ShShShShSh! On frequencies like 121.1 which is approach for the Orlando area.
Since I have now moved to the Dallas area, the problem has changed to a much worse condition. Now when I key the mike, I sometimes get the autopilot kicking off, sometimes the radio kicks off, and the last couple of flights, the electrically dependent engine will all but die while I have the mike key depressed. I am not finished with living, so I have to find and fix this before I fly again.
This sounds like two separate problems. What kind of airplane
and where is the comm antenna installed?
I have no real knowledge of electrical things, but I used to think that I could follow directions and connect wires. I am beginning to think I may have been wrong about that!
I can not think of anything that would cause this phenomenon when the mike is keyed. Hopefully you can come up with some direction that I can follow to discover a cause. I have come to think that somehow I must be getting a voltage on this ground line that is then feeding back to all the equipment in the plane. The thing is, I really don’t have any clue about how I would go about testing for such a thing even if that turns out to be the problem.
Let's get all the data before we begin picking
at straws . . .
What I hope is that something in this problem will strike a pattern to you that will allow you to give me a direction to look for the problem. If it does, I would need some pretty explicit directions as to what and how to test whatever you think would make sense to test.
I know this is rambling and non-specific, but if you should need any more info, I will be happy to try and provide it.
Thanks for all the help you have given all of us in the past and hopefully you can come up with a little assistance for me here.
Not a problem, its what we do here. But at the
same time, know that diagnostics by e-mail are
fraught with risk for lack of understanding
and forcing unnecessary delays. Are there
no builders and/or radio cognizant acquaintances
local to you that could participate in this
activity? I suspect that the root cause is
simple . . . it usually is.
Have you physically checked the antenna coax
from the back of the radio to the antenna? Unhook
the coax, tug on the connectors at both ends.
See if they can be 'twisted' on the wire. Their
attachment should be quite robust 5=10 pounds
of pull or twisting with the fingers should
produce NO motion between connector and coax.
The noise is, I believe, a separate issue.
Have you attempted to locate potential antagonists?
Pull all breakers/fuses except for those necessary
to run the radio and engine. Does the noise go away?
Thank you,
Bill
Bob . . . [quote][b]
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nuckolls.bob(at)aeroelect
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| Posted: Sun Aug 30, 2015 9:10 am Post subject: Request for some direction and advise |
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At 11:32 AM 8/30/2015, you wrote:
I appreciate any assistance I can get. A difficult to hear some transmissions is one thing but with the engine now involved, that is a major problem.
Yeah . . . that tends to get your attention . . .
I will try and answer your questions in order.
This is a Lancair Legacy. Fiberglass not carbon fiber, although some components are carbon fiber. No carbon fiber near the radio or antenna installation.
The comm. Antenna is a Advanced Electronics antenna as is described here
http://www.aircraftspruce.com/catalog/avpages/antennasystems.php
The antenna is installed on the right side if the fuselage, inside just behind the rear luggage bulkhead. The antenna is long enough that it forms the shape of a “C” on the right side of the fuselage. It extends from about the center line on the top to the center line on the bottom. The bottom end of the antenna is very close, within an inch, of one of the rudder cables. The rudder cable does not connect to a ground due to the plane being fiberglass.
What are the chronological and service ages of
this installation. I.e. how long has the airplane
been flying and how many hours in that time. Noises
aside, I presume that the comm radio has performed
satisfactorily until now?
I just moved to the airport at Mesquite, TX on Friday. I have been on their waiting list for 20 months. There is no radio shop on the field and I have not yet met any builders there.
Unless they are related, I hope to find and fix the kicking off of the autopilot and radio and the shutting down of the engine before the static.
They are almost certainly unrelated. Noises in
receivers at selected frequencies have little
or nothing in common with energy from your transmitter
getting into places it doesn't belong.
The later symptom screams of broken coax shield
connection. Energy from your transmitter is supposed
to be 'piped' to the antenna . . . generally away
from potential victims before being gracefully launched
into the ether.
should your coax shield become ungrounded,
PARTICULARLY at the radio end, the entire
coax becomes a very disorderly antenna that
radiates stuff in and around the cockpit
with energy that might prove deleterious
to performance of the various systems. This
is a relatively rare condition but made a
greater risk in OBAM aviation where appliances
are NOT generally tested for immunity to strong
RF . . . a thing we do religiously in TC aircraft.
But even WITH proper homage paid at the altar
of the EMI gods, ALL systems have a limit as
to how much mischievous energy can be ignored.
The fact that you have TWO affected systems
suggests that the energy levels involved are
large and almost certainly associated with
loss of integrity in that 'pipe' . . . the
antenna feed line.
I will check the coax connectors to make certain that they are tight. Are there any scenarios that come to mind where the keying of the mike could cause other equipment to shut down?
They are probably manifestations arising from
a single cause.
Does this sound like voltage is being introduced onto the ground system? Does it sound like a short somewhere? Surely the radio, coax, antenna could not be putting out radiation that would shut down the other equipment???
Under the WRONG condition cited above, the
coax is no longer a coax . . . and it easily
joins turns the best behaved transmitter into
a cockpit thug.
Other than the coax connectors, where would you look first? Second?
If we had my toolbox there, I'd first dummy load
the transmitter and note that the effect goes
away. I'd also put the antenna analyzer on
your comm antenna coax to confirm the cockpit
thug hypothesis. After that, it's pretty much
touchy-feely activities to deduce from whence
the pipe is leaking.
Bob . . . [quote][b]
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Sun Aug 30, 2015 2:19 pm Post subject: Request for some direction and advise |
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At 01:14 PM 8/30/2015, you wrote:
| Quote: | | I bought the radio and other electronics along about 2005. The FAA deemed the plane airworthy in Dec of 2010. |
yeahhh . . . but . . .
| Quote: | I now have 110 hours on it. The radio has always been a little squirrelly. I previously had problems
with the autopilot dropping out but not shutting off. The TruTrak folks suggested I install a connector
that has capacitors in it. That seemed to help for a while. |
that was advice from TruTrak? to change the connector
on THEIR product? Given the technological roots of
this company I am . . . shall we say . . . mystified?
| Quote: | | Last year I had an instance where I could not hear ATC but they could hear me. Not caused by the hiss, but just dead air. I managed to find another controller that I could hear and he relayed what they were trying to tell me. I also can not pick up any ATIS until within 20 miles from any station that I have tried and I think that is supposed to be closer to 50 miles. |
Clearly, not all is right with your antenna system
(presuming the radio is okay) . . . inability to
hear you is consistent with a severe transmission
line problem or perhaps even a broke antenna.
How hard would it be to remove your antenna for
bench testing?
| Quote: |
Several years ago, a friend checked the SWR on the antenna from the COAX connector at the radio and it was less than 2 at the time. I don’t remember the exact number but it was low. |
Normally, low SWR is a good thing but you need to
look at then antenna over its full range of
intended operation. "SWR" instruments are not
all necessarily golden either . . . I've pitched
a couple of cheapies in the trash after discovering
serious discrepancies in displayed readings versus
physical realities.
Bob . . . [quote][b]
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bbradburry(at)verizon.net
Guest
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| Posted: Sun Aug 30, 2015 7:21 pm Post subject: Request for some direction and advise |
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I saw where someone else on the list a while back was discussing adding that connector to their TruTrak at the company’s suggestion. It is supposed to keep RFI out as I recall.
The antenna is glassed in and not removable, I tried to attach it with tape, but I could not get it to stay in place so I just glassed it in. I do have a second antenna that I could try if I don’t find anything with the coax. I only have a Volt-Ohm meter so I don’t think I could bench test the antenna.
Bill
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III
Sent: Sunday, August 30, 2015 5:18 PM
To: Bill Bradburry; aeroelectric-list(at)matronics.com
Subject: RE: Request for some direction and advise
At 01:14 PM 8/30/2015, you wrote:
I bought the radio and other electronics along about 2005. The FAA deemed the plane airworthy in Dec of 2010.
yeahhh . . . but . . .
I now have 110 hours on it. The radio has always been a little squirrelly. I previously had problems
with the autopilot dropping out but not shutting off. The TruTrak folks suggested I install a connector
that has capacitors in it. That seemed to help for a while.
that was advice from TruTrak? to change the connector
on THEIR product? Given the technological roots of
this company I am . . . shall we say . . . mystified?
Last year I had an instance where I could not hear ATC but they could hear me. Not caused by the hiss, but just dead air. I managed to find another controller that I could hear and he relayed what they were trying to tell me. I also can not pick up any ATIS until within 20 miles from any station that I have tried and I think that is supposed to be closer to 50 miles.
Clearly, not all is right with your antenna system
(presuming the radio is okay) . . . inability to
hear you is consistent with a severe transmission
line problem or perhaps even a broke antenna.
How hard would it be to remove your antenna for
bench testing?
Several years ago, a friend checked the SWR on the antenna from the COAX connector at the radio and it was less than 2 at the time. I dont remember the exact number but it was low.
Normally, low SWR is a good thing but you need to
look at then antenna over its full range of
intended operation. "SWR" instruments are not
all necessarily golden either . . . I've pitched
a couple of cheapies in the trash after discovering
serious discrepancies in displayed readings versus
physical realities.
Bob . . . | Quote: | | http://www.matronics.com/Navigator?AeroElectric-List |
0123456789
[quote][b]
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Eric M. Jones
Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts
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| Posted: Wed Sep 02, 2015 5:43 am Post subject: Re: Request for some direction and advise |
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My Father (who worked on Westinghouse's part of the USN Vanguard rocket), related to me the ultimate failure with it:
Test techs would unplug all the tubes (yes it had tubes) test the tubes and stick them back into their sockets....time after time after time. (One thinks they must also have unplugged every module too).
So everything tested fine, and when the rocket took off, all the vibration caused the tube sockets to quit making contact because they were worn out.
Whether or not this was entirely true, the lesson remains: Contacts are the first place to look for most sorts of electrical problems. For the remainder, contacts probably had something to do with the failure in the first place.
Contact failure can occur in ways you would never suspect. In the medical field people get shocked because the plating has worn off brass contacts, which now behave as diodes. The HF used in surgery ("Bovies") now generates HV DC instead of the HF AC used in electrosurgery. OUCH!
So always suspect connections first. Both intended and unintended.
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net |
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yellowduckduo(at)gmail.co
Guest
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| Posted: Wed Sep 02, 2015 12:42 pm Post subject: Request for some direction and advise |
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I love this story Eric
Of course I just spent two days tracking a glitch that turned out to be
a poor digital signal connection in a good looking shiny solder joint...
Ken
do not archive
On 02/09/2015 9:43 AM, Eric M. Jones wrote:
| Quote: |
My Father (who worked on Westinghouse's part of the USN Vanguard rocket), related to me the ultimate failure with it:
Test techs would unplug all the tubes (yes it had tubes) test the tubes and stick them back into their sockets....time after time after time. (One thinks they must also have unplugged every module too).
So everything tested fine, and when the rocket took off, all the vibration caused the tube sockets to quit making contact because they were worn out.
Whether or not this was entirely true, the lesson remains: Contacts are the first place to look for most sorts of electrical problems. For the remainder, contacts probably had something to do with the failure in the first place.
Contact failure can occur in ways you would never suspect. In the medical field people get shocked because the plating has worn off brass contacts, which now behave as diodes. The HF used in surgery ("Bovies") now generates HV DC instead of the HF AC used in electrosurgery. OUCH!
So always suspect connections first. Both intended and unintended.
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net
|
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