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Radio Noise

 
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gra9933(at)bellsouth.net
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PostPosted: Sun Jan 15, 2006 6:00 am    Post subject: Radio Noise Reply with quote

Listers:
I have a radio noise problem. I've checked the archives, and I can't
find a similar problem having been discussed on the RV list or the
AeroElectric list. Here are the symptoms:

1) When I turn on the master switch, I get noise in my headset that
emanates from the VHF radio. I know its the VHF radio because the noise
volume can be controlled with the volume knob on the radio. The radio is
an Apollo GX-60. The noise sounds exactly like the squelch is turned on
- just some static. The noise is usually constant, but sometimes goes
intermittent. The radio frequency does not matter.

2) I have an ACS2002 engine monitor. The noise is correlated to the
engine monitor's function. The noise will go away (or go to
intermittent) when I start the ACS2002 in calibration mode. When I
return to normal mode, the noise is back. If I pull the fuse for the
ACS, the noise goes away entirely and does not come back. If I pull the
audo connection d-sub from the back of the ACS screen, there is no
change at all - still noisy.

3) This is all with the engine OFF, keyswitch OFF, every other accessory
turned off.

I have 2 theories, based on the very little avionics knowledge that I have.
Theory A) Some sensor on the ACS is causing RF noise. I don't know which
one - I may have to start disconnecting them one at a time (on my back,
under the panel) to try and isolate.
Theory B) My antenna installation is screwed up somehow. I have a 45
bent whip antenna, standard from Aircraft Spruce, installed on the belly
under the pilot's seat. Standard coax runs from radio to antenna. Center
conductor terminated with a ring terminal and secured onto antenna.
Outer braided conducter terminated at a ring terminal and screwed into a
nutplate on the structure for ground. Any way to test that this is
normal/ok/etc?

Thanks to anyone that might have a suggestion,

Jordan Grant
RV-6 N198G
Done - except for last minute problems and first flight!


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khorton01(at)rogers.com
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PostPosted: Sun Jan 15, 2006 6:31 am    Post subject: Radio Noise Reply with quote

On 15 Jan 2006, at 08:59, Jordan Grant wrote:

Quote:


Listers:
I have a radio noise problem. I've checked the archives, and I
can't
find a similar problem having been discussed on the RV list or the
AeroElectric list. Here are the symptoms:

1) When I turn on the master switch, I get noise in my headset that
emanates from the VHF radio. I know its the VHF radio because the
noise
volume can be controlled with the volume knob on the radio. The
radio is
an Apollo GX-60. The noise sounds exactly like the squelch is
turned on
- just some static. The noise is usually constant, but sometimes goes
intermittent. The radio frequency does not matter.

2) I have an ACS2002 engine monitor. The noise is correlated to the
engine monitor's function. The noise will go away (or go to
intermittent) when I start the ACS2002 in calibration mode. When I
return to normal mode, the noise is back. If I pull the fuse for the
ACS, the noise goes away entirely and does not come back. If I pull
the
audo connection d-sub from the back of the ACS screen, there is no
change at all - still noisy.

3) This is all with the engine OFF, keyswitch OFF, every other
accessory
turned off.

I have 2 theories, based on the very little avionics knowledge that
I have.
Theory A) Some sensor on the ACS is causing RF noise. I don't know
which
one - I may have to start disconnecting them one at a time (on my
back,
under the panel) to try and isolate.
Theory B) My antenna installation is screwed up somehow. I have a 45
bent whip antenna, standard from Aircraft Spruce, installed on the
belly
under the pilot's seat. Standard coax runs from radio to antenna.
Center
conductor terminated with a ring terminal and secured onto antenna.
Outer braided conducter terminated at a ring terminal and screwed
into a
nutplate on the structure for ground. Any way to test that this is
normal/ok/etc?

Thanks to anyone that might have a suggestion,

It might be instructive to see if you hear the noise in a handheld
radio. That might help figure out whether it is a radiated noise
problem, or something that is conducted through the wiriing or
airframe. If the handheld hears the noise, then it must be radiated
noise from the engine monitor or its sensors. If the handheld
doesn't hear the noise, then it has to be transmitted through the
power lines or grounds. I think.

Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://www.kilohotel.com/rv8


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kbeene(at)citilink.com
Guest





PostPosted: Sun Jan 15, 2006 6:51 am    Post subject: Radio Noise Reply with quote

Grant,

This sounds like a RFI problem. I saw this problem with an engine monitor
on a friend's airplane. He thought he had a radio problem because he
couldn't hear the tower more than 10 miles out. The RFI was desensitizing
this receiver. He didn't have the engine monitor on a switch so he had not
tried to turn it off. With my handheld radio it was easy to identify the
source.

The noise is usually generated by the CPU clock in the computer (try putting
your radio next to your home computer). After we removed the fuse on the
ACS, the radio worked properly. Some electronics designers do not worry
about electromagnetic compatibility (EMC).

He contacted ACS and they sent some updated cables or some additional
shielding to reduce the problem. You should avoid running the cables from
the radio and engine monitor parallel to each other. These problems are
best fixed during the design with RF bypass capacitors and RF chokes
(torids) around the signals and power leads before they exit a properly
shielded enclosure.

Ken
RV-6A N94kb
RV-4 under construction

Quote:
Listers:
I have a radio noise problem. I've checked the archives, and I can't
find a similar problem having been discussed on the RV list or the
AeroElectric list. Here are the symptoms:

1) When I turn on the master switch, I get noise in my headset that
emanates from the VHF radio. I know its the VHF radio because the noise
volume can be controlled with the volume knob on the radio. The radio is
an Apollo GX-60. The noise sounds exactly like the squelch is turned on
- just some static. The noise is usually constant, but sometimes goes
intermittent. The radio frequency does not matter.


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SSampson.SLN21(at)london.
Guest





PostPosted: Sun Jan 15, 2006 11:45 am    Post subject: Radio Noise Reply with quote

Jordan - be sure the antenna is bolted on tight with a good attachment of
the screen to the ground plane. Jus a thought, Steve.

---


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jeffpoint



Joined: 10 Jan 2006
Posts: 72
Location: MKE

PostPosted: Sun Jan 15, 2006 12:04 pm    Post subject: Radio Noise Reply with quote

One thing to keep in mind while troubleshooting radio noise on the
ground- If you are running off ships power with no charger or power
supply attached, then you are likely at less than the required voltage
for the radio equipment (including the noise-filtering apparatus) to
work properly. With the engine running and the alternator alternating,
your system voltage is around 14V (give or take .5) but with a less than
fully charged battery, with a load, it is down closer to 12V. For
example, the DRE244 intercom (a great unit BTW) requires 12.5V for it's
noise filtering stuff to work, and I had all sorts of noise problems
(mostly EFI related from the Dynon D-10) until I figured this out. I
put a charger on the battery, brought the voltage up and 90% of my noise
problems disappeared instantly. The engine noise took care of the
reamining 10% Wink

Try connecting a battery charger to your battery to bring the voltage
up, ot try it with the engine (and alternator) running.

Jeff Point
RV-6
Milwaukee
Quote:




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_________________
Jeff Point
RV-6
Milwaukee WI
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gra9933(at)bellsouth.net
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PostPosted: Sun Jan 15, 2006 3:45 pm    Post subject: Radio Noise Reply with quote

Jeff:
I went troubleshooting today and, of course, there was no trouble! I
just received my super-duper Odyssey battery charger the other day, and
I charged up the battery overnight. This afternoon, there was no noise
on my radio! I think that may have been the problem - just lowish
voltage on the battery. As part of my troubleshooting, I borrowed a
handheld VHF radio and waved it around inside the cockpit. It picked up
a lot of noise! The screen on the ACS2002 seemed to be radiating a fair
amount of it. However, the GX60 was quiet.

If it happens again with a fully charged battery or the alternator
running, I'll get suspicious. Until then, I'm considering it to not be a
problem. I'm glad I put the question out there on the RV List, though -
hopefully the next guy that runs into this will search the archives and
find out the answer.

Thanks a lot to everyone that responded,

Jordan Grant
RV-6 N198G
Ready to fly if only my engine would run...
Jeff Point wrote:

Quote:


One thing to keep in mind while troubleshooting radio noise on the
ground- If you are running off ships power with no charger or power
supply attached, then you are likely at less than the required voltage
for the radio equipment (including the noise-filtering apparatus) to
work properly. With the engine running and the alternator alternating,
your system voltage is around 14V (give or take .5) but with a less than
fully charged battery, with a load, it is down closer to 12V. For
example, the DRE244 intercom (a great unit BTW) requires 12.5V for it's
noise filtering stuff to work, and I had all sorts of noise problems
(mostly EFI related from the Dynon D-10) until I figured this out. I
put a charger on the battery, brought the voltage up and 90% of my noise
problems disappeared instantly. The engine noise took care of the
reamining 10% Wink

Try connecting a battery charger to your battery to bring the voltage
up, ot try it with the engine (and alternator) running.

Jeff Point
RV-6
Milwaukee


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