Matronics Email Lists Forum Index Matronics Email Lists
BBS Forum Interface to the Matronics Email Lists
 
 Get Email Distribution Too!Get Email Distribution Too!    FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Excessive noise on VHF radio when Transmitting

 
Post new topic   Reply to topic    Matronics Email Lists Forum Index -> Allegro-List
View previous topic :: View next topic  
Author Message
hgmckay



Joined: 23 May 2006
Posts: 374

PostPosted: Tue Jun 14, 2016 1:40 pm    Post subject: Excessive noise on VHF radio when Transmitting Reply with quote

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(at)bellsouth.net


- The Matronics Allegro-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?Allegro-List



Hugh.vcf
 Description:

Download
 Filename:  Hugh.vcf
 Filesize:  79 Bytes
 Downloaded:  135 Time(s)

Back to top
View user's profile Send private message
Brian Carpenter



Joined: 06 Mar 2008
Posts: 24
Location: TAYLOR, AZ

PostPosted: Tue Jun 14, 2016 3:08 pm    Post subject: Excessive noise on VHF radio when Transmitting Reply with quote

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 if that ground connection has broke somehow. Possibly the final output transistors on the radio itself may be bad and you're putting out very low power so the noise covers the amount of audio going out. Possibly check the outgoing 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(at)bellsouth.net (hgmckay(at)bellsouth.net)> wrote:
Quote:
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(at)bellsouth.net (hgmckay(at)bellsouth.net)


<Hugh.vcf>


- The Matronics Allegro-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?Allegro-List

_________________
BRIAN N3081X
Back to top
View user's profile Send private message
N456TS



Joined: 15 Aug 2015
Posts: 58

PostPosted: Wed Jun 15, 2016 8:26 pm    Post subject: Re: Excessive noise on VHF radio when Transmitting Reply with quote

There are two main noise sources when the engine is running. Generator and spark plugs. I would check all grounds again. Do you have a good meter which can measure capacitance? Sometimes electrolyte caps can dry out without puffing. You could confirm your noise source by disabling the generator and running the engine. Does the static become better/change when running on only one ignition?

- The Matronics Allegro-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?Allegro-List

_________________
N456TS
Back to top
View user's profile Send private message
hgmckay



Joined: 23 May 2006
Posts: 374

PostPosted: Thu Jun 16, 2016 6:12 am    Post subject: Excessive noise on VHF radio when Transmitting Reply with quote

N456TS,

How do I disable the generator on a Rotax 912?

Hugh G. McKay III, P.E. Fellow, L.M. ASCE
Senior Consultant
Worldwide Engineering Inc.
4090 North NC Hwy. 16
Denver, NC 28037

Ph. 704-661-8271
Fax 704-483-5466
email hgmckay(at)bellsouth.net
http://www.wwegeo.com
--


- The Matronics Allegro-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?Allegro-List
Back to top
View user's profile Send private message
N456TS



Joined: 15 Aug 2015
Posts: 58

PostPosted: Tue Jun 21, 2016 6:00 pm    Post subject: Re: Excessive noise on VHF radio when Transmitting Reply with quote

hgmckay wrote:
How do I disable the generator on a Rotax 912?


Sorry for the delay in reply. You can disconnect the two "G" wires at the regulator. Tape and isolate them from touching anything including each other.


- The Matronics Allegro-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?Allegro-List

_________________
N456TS
Back to top
View user's profile Send private message
N456TS



Joined: 15 Aug 2015
Posts: 58

PostPosted: Mon Jul 04, 2016 8:26 am    Post subject: Re: Excessive noise on VHF radio when Transmitting Reply with quote

Did you find your static source?

- The Matronics Allegro-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?Allegro-List

_________________
N456TS
Back to top
View user's profile Send private message
hgmckay



Joined: 23 May 2006
Posts: 374

PostPosted: Tue Jul 05, 2016 4:38 am    Post subject: Excessive noise on VHF radio when Transmitting Reply with quote

N456TS,

I have been busy with family, the holiday and other matters since my last
communication. I will resume the search hopefully this week.

Hugh G. McKay III, P.E. Fellow, L.M. ASCE
Senior Consultant
Worldwide Engineering Inc.
4090 North NC Hwy. 16
Denver, NC 28037

Ph. 704-661-8271
Fax 704-483-5466
email hgmckay(at)bellsouth.net
http://www.wwegeo.com
--


- The Matronics Allegro-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?Allegro-List
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Matronics Email Lists Forum Index -> Allegro-List All times are GMT - 8 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


Powered by phpBB © 2001, 2005 phpBB Group