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jpx(at)Qenesis.com
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 Posted: Mon Aug 10, 2009 5:25 am Post subject: Radio Noise |
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} I think your friend suffers from what I consider to be the most common cause
} of dissatisfaction with VHF COMM performance in OBAM aircraft... unrealistic
} expectations!
Unfortunately the situation is more annoying than that. There is usually
difficulty talking with the tower. Sometimes it is bad enough that clearance
has been denied. This is very inconvenient since it is the home base of this
aircraft 
| Quote: | What, if any other accessories are operating on the
airplane during this test. Try pulling all other breakers/
fuses except radio/audio system to search out possible
cause/effect on board the aircraft. In particular, make
sure the alternator's regulator is not powered up.
|
There is little else electrical in the aircraft. We tried turning off the
transponder. There are no lights, fuel pump or even turn coordinator.
Switching off the alternator should also power off the regulator.
| Quote: | Does the noise go away when you disconnect the antenna?
Have you checked for presence of this noise while away
from the field? The directional effects suggest possible
local source on the ground.
|
The noise and the receive audio continue identically, not even a click as
the antenna is connected and disconnected. This baffles me.
The noise persists away from the airport. When calling up the tower from
10 miles out it is difficult to understand the controller. Sometimes the
controller also has trouble understanding the transmissions from the aircraft.
Changing the direction of the aircraft sometimes helps.
| Quote: | This is one of Ed King's earliest crystal synthesized radios
that came out about 1975 as I recall. Have you checked to see
if this radio still qualifies under tightened frequency
accuracy and receiver bandwidth requirements were levied for
8.33 Khz channel spacing?
|
The radio is 25KHz spacing, according to the little brochure that suffices
as the operation manual.
| Quote: | Also, check performance at the top end of the comm frequency range with
a remotely located hand held for weak signal. See if the problem is
frequency sensitive.
|
Ground is 118.40, Tower is 120.10 and the ATIS is 125.67.
I haven't tried anything at the top end, but hopefully will get a chance
to do so this week when I check the antenna cables and antenna by patching
in a handheld.
Thanks !
Jeff Page
Dream Aircraft Tundra #10
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mrspudandcompany(at)veriz
Guest
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| Posted: Mon Aug 10, 2009 6:24 am Post subject: Radio Noise |
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Kellym
Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ
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| Posted: Mon Aug 10, 2009 1:16 pm Post subject: Radio Noise |
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Two suggestions. If possible, find another aircraft with same model
radio, that you can swap yours into, and see how it performs.
Check your antenna cable thoroughly, substitute another cable and
antenna if possible. I had similar problems with old antenna cable that
turned out to have a cold solder joint for the shield on the radio end,
allowing lots of RF to leak back into the radio. New cable, problem gone.
If the radio has been bench checked with no problems, then the problem
has to be between the radio and the antenna, likely bad connection or no
connection.
One last long shot...turn coordinator or turn and bank are normally
wired directly to main bus to be always powered. If it has a noisy
motor, theoretically could be source even though nothing else is turned on.
Jeff Page wrote:
| Quote: |
} I think your friend suffers from what I consider to be the most common
cause
} of dissatisfaction with VHF COMM performance in OBAM aircraft...
unrealistic
} expectations!
Unfortunately the situation is more annoying than that. There is usually
difficulty talking with the tower. Sometimes it is bad enough that
clearance
has been denied. This is very inconvenient since it is the home base of
this
aircraft
> What, if any other accessories are operating on the
> airplane during this test. Try pulling all other breakers/
> fuses except radio/audio system to search out possible
> cause/effect on board the aircraft. In particular, make
> sure the alternator's regulator is not powered up.
There is little else electrical in the aircraft. We tried turning off the
transponder. There are no lights, fuel pump or even turn coordinator.
Switching off the alternator should also power off the regulator.
> Does the noise go away when you disconnect the antenna?
> Have you checked for presence of this noise while away
> from the field? The directional effects suggest possible
> local source on the ground.
The noise and the receive audio continue identically, not even a click as
the antenna is connected and disconnected. This baffles me.
The noise persists away from the airport. When calling up the tower from
10 miles out it is difficult to understand the controller. Sometimes the
controller also has trouble understanding the transmissions from the
aircraft.
Changing the direction of the aircraft sometimes helps.
> This is one of Ed King's earliest crystal synthesized radios
> that came out about 1975 as I recall. Have you checked to see
> if this radio still qualifies under tightened frequency
> accuracy and receiver bandwidth requirements were levied for
> 8.33 Khz channel spacing?
The radio is 25KHz spacing, according to the little brochure that suffices
as the operation manual.
> Also, check performance at the top end of the comm frequency range with
> a remotely located hand held for weak signal. See if the problem is
> frequency sensitive.
Ground is 118.40, Tower is 120.10 and the ATIS is 125.67.
I haven't tried anything at the top end, but hopefully will get a chance
to do so this week when I check the antenna cables and antenna by patching
in a handheld.
Thanks !
Jeff Page
Dream Aircraft Tundra #10
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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD |
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mhcrowder
Joined: 10 Jan 2006
Posts: 42
Location: Cary, NC
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| Posted: Tue Aug 11, 2009 5:37 am Post subject: Re: Radio Noise |
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I think you are on the right track by using a second radio connected into the aircraft's antenna cable to compare reception and transmission. And even better with a handheld, since you are also isolating the power side of things. Hang in there, you'll get the problem worked out!
| jpx(at)Qenesis.com wrote: |
I haven't tried anything at the top end, but hopefully will get a chance
to do so this week when I check the antenna cables and antenna by patching
in a handheld.
Thanks !
Jeff Page
Dream Aircraft Tundra #10 |
| | - 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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_________________
Michael Crowder
Jabiru 3300A w/ Hyd Lifters
EFI |
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jpx(at)Qenesis.com
Guest
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| Posted: Tue Aug 11, 2009 10:10 am Post subject: Radio Noise |
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| Quote: | Two suggestions. If possible, find another aircraft with same model
radio, that you can swap yours into, and see how it performs.
|
The owner of the aircraft is going to ask the avionics shop if they have
another we can test with. I am not hopeful.
| Quote: | Check your antenna cable thoroughly, substitute another cable and
antenna if possible.
|
The owner spent $1000 to have another antenna and cable installed on the
aircraft. All but the soldered on pigtail cable at the radio rack was
installed new. The pigtail was examined and a poor solder joint redone.
I plan to make a patch cable that we can use to connect a handheld right
to the jack in the radio rack to test all of it. Something is truly weird,
since connecting and disconnecting the antenna makes no difference at all
in the reception.
| Quote: | turn coordinator or turn and bank are normally wired directly to main
bus to be always powered.
|
Such as basic panel that there are no electrical devices like this in the
plane.
| Quote: | I believe you said the radio was bench tested and found to be operational.
If this is the case, then from your description of the problem, it appears
that it is either the (1) antenna and/or cable, (2) power/ground wiring, or
(3) mike/speaker wiring.
|
I am following up on the antenna cable first, since disconnecting it has no
effect at all, which seems very strange. We isolated the headset jacks at
the panel the other day without improvement. If we are unable to solve the
problem from the antenna side of it, it will probably be faster to just
rewire the plane than to try to follow all the old wires to see if they are
connected to the right place.
Thanks for everyone's suggestions.
Jeff Page
Dream Aircraft Tundra #10
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Kellym
Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ
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| Posted: Tue Aug 11, 2009 3:21 pm Post subject: Radio Noise |
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You want another aircraft with the same model radio that works okay.
NOT to test his radio in your aircraft, but to test YOUR radio in his
airplane. Completely eliminates any install issues with your aircraft
and isolates on the radio itself. If behavior goes away in second
airplane, the problem is your install. If not, it is your radio.
Jeff Page wrote:
| Quote: |
> Two suggestions. If possible, find another aircraft with same model
> radio, that you can swap yours into, and see how it performs.
The owner of the aircraft is going to ask the avionics shop if they have
another we can test with. I am not hopeful.
|
| | - 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:
http://www.matronics.com/Navigator?AeroElectric-List |
|
_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD |
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n395v
Joined: 10 Jan 2006
Posts: 450
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| Posted: Wed Aug 12, 2009 4:04 am Post subject: Re: Radio Noise |
|
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| Quote: | } I think your friend suffers from what I consider to be the most common cause
} of dissatisfaction with VHF COMM performance in OBAM aircraft... unrealistic
} expectations!
|
I think he suffers from an equipment or installation problem.
I have owned and flown several OBAM aircraft and they all have crystal clear reception and transmission over a good distance.
Keep troubleshooting till it works as it should.
| | - 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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Milt |
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airelectricjim
Joined: 09 Jan 2009
Posts: 11
Location: Augusta GA USA
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| Posted: Wed Aug 12, 2009 7:50 am Post subject: Radio Noise |
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Hi, Jeff,
Is the radio's rf connector making contact with the jack in the rack?
Hard to check, but rather important.
Blue skies and tailwinds to all
Jim
CH-801
DeltaHawk diesel
90% done 120% left
| | - 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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_________________
Jim
Zenith CH801
DeltaHawk diesel
jmcburney@pobox.com |
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