Today's Message Index:
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1. 02:40 PM - Excessive noise on VHF radio when Transmitting (Hugh McKay)
2. 04:08 PM - Re: Excessive noise on VHF radio when Transmitting (Allegro)
3. 07:40 PM - Re: RotaxEngines-List: Excessive noise on VHF radio when Transmitting (Guy Buchanan)
Message 1
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Subject: | Excessive noise on VHF radio when Transmitting |
Gentlemen,
I have a noise problem on the VHF radio system in my plane when I
attempt to transmit. In fact The other day while flying through Class C
airspace the approach controller was telling me that my transmission was
broken and had so much noise he could hardly understand what I was
saying. I also hear the noise in my headphones when I transmit, not when
receiving.
I have visually checked all the ground connections on the plane and they
are clear of corrosion and are tight. While on the ground with the
engine not running the radio transmission is fine with no problems. The
problem only occurs when the engine is running. The noise sounds like
the frequency of the rotating generator on the back of the engine which
is a Rotax 912 UL. The audible frequency can be heard to vary with the
engine rpm. It is =9Cdirty=9D noise. My radio is a panel
mounted ICOM IC-A200. I also have two 10,000 mF capacitors connected in
parallel between the voltage regulator and ground as noise filters. I
have visually checked the two capacitors, and they seem to be in good
order (i.e. no swelling or distortion). The antenna is a Comant VHF CI
121 using a quarter wave ground plane. I have had no problems with this
system for ten years.
Here are the specifics:
Aircraft Allegro 2000 LSA
Engine Rotax 912 UL
TSN 741 hrs
Radio ICOM IC-A200
Antenna Comant VHF CI 121
Any and all advice as to how to identify what is causing the problem and
how to correct it would be appreciated.
Hugh G. McKay III, P.E.
N661WW
email hgmckay@bellsouth.net
Message 2
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Subject: | Re: Excessive noise on VHF radio when Transmitting |
Check the ground connection on the antenna. Mine has some silver tape on the
inside of the fiberglass to make your ground, possibly use ohmmeter to see i
f that ground connection has broke somehow. Possibly the final output transi
stors on the radio itself may be bad and you're putting out very low power s
o the noise covers the amount of audio going out. Possibly check the outgoin
g power of the radio. May have to be done at an avionic shop.
Sent from my Brian's
iPhone
> On Jun 14, 2016, at 14:39, Hugh McKay <hgmckay@bellsouth.net> wrote:
>
> Gentlemen,
>
> I have a noise problem on the VHF radio system in my plane when I attempt t
o transmit. In fact The other day while flying through Class C airspace the a
pproach controller was telling me that my transmission was broken and had so
much noise he could hardly understand what I was saying. I also hear the no
ise in my headphones when I transmit, not when receiving.
>
> I have visually checked all the ground connections on the plane and they a
re clear of corrosion and are tight. While on the ground with the engine not
running the radio transmission is fine with no problems. The problem only o
ccurs when the engine is running. The noise sounds like the frequency of the
rotating generator on the back of the engine which is a Rotax 912 UL. The a
udible frequency can be heard to vary with the engine rpm. It is =9Cdi
rty=9D noise. My radio is a panel mounted ICOM IC-A200. I also have t
wo 10,000 mF capacitors connected in parallel between the voltage regulator a
nd ground as noise filters. I have visually checked the two capacitors, and t
hey seem to be in good order (i.e. no swelling or distortion). The antenna i
s a Comant VHF CI 121 using a quarter wave ground plane. I have had no probl
ems with this system for ten years.
>
> Here are the specifics:
> Aircraft Allegro 2000 LSA
> Engine Rotax 912 UL
> TSN 741 hrs
> Radio ICOM IC-A200
> Antenna Comant VHF CI 121
>
> Any and all advice as to how to identify what is causing the problem and h
ow to correct it would be appreciated.
>
> Hugh G. McKay III, P.E.
> N661WW
> email hgmckay@bellsouth.net
> <Hugh.vcf>
Message 3
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Subject: | Re: RotaxEngines-List: Excessive noise on VHF radio when |
Transmitting
Visually checking the antenna grounds isn't going to cut it. I'd refresh
them manually. I have to do this once a year at least. (Stainless bolt
on aluminum antenna base. Not great.)
2nd guess is pre-existing ground loop is now picking up charging noise
due to a weakness in the system elsewhere. (Grounds?) You gotta be
religious about ground loops.
*_Guy Buchanan_*
Assistant Scoutmaster Troop 680
760.809.6145
gebuchanan@cox.net<mailto:gebuchanan@cox.net>
www.troop680.org
On 6/14/2016 2:39 PM, Hugh McKay wrote:
> Gentlemen,
> I have a noise problem on the VHF radio system in my plane when I
> attempt to transmit. In fact The other day while flying through Class
> C airspace the approach controller was telling me that my transmission
> was broken and had so much noise he could hardly understand what I was
> saying. I also hear the noise in my headphones when I transmit, not
> when receiving.
> I have visually checked all the ground connections on the plane and
> they are clear of corrosion and are tight. While on the ground with
> the engine not running the radio transmission is fine with no
> problems. The problem only occurs when the engine is running. The
> noise sounds like the frequency of the rotating generator on the back
> of the engine which is a Rotax 912 UL. The audible frequency can be
> heard to vary with the engine rpm. It is dirty noise. My radio is a
> panel mounted ICOM IC-A200. I also have two 10,000 mF capacitors
> connected in parallel between the voltage regulator and ground as
> noise filters. I have visually checked the two capacitors, and they
> seem to be in good order (i.e. no swelling or distortion). The antenna
> is a Comant VHF CI 121 using a quarter wave ground plane._*I have had
> no problems with this system for ten years.*_
> _**_
> Here are the specifics:
> Aircraft Allegro 2000 LSA
> Engine Rotax 912 UL
> TSN 741 hrs
> Radio ICOM IC-A200
> Antenna Comant VHF CI 121
> Any and all advice as to how to identify what is causing the problem
> and how to correct it would be appreciated.
> Hugh G. McKay III, P.E.
> N661WW
> email hgmckay@bellsouth.net
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