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Looking for help to fix radio noise?

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Eugene Zimmerman

Joined: 10 Jan 2006
Posts: 392

Posted: Wed Apr 07, 2010 5:34 pm Post subject: Looking for help to fix radio noise?

Kolb friends,



I  have been using an A5 ICOM  for several years with an external antenna.  It gives me good service in reception and transmitting and I am satisfied with it except for one problem, and  I know next to nothing about radio tech.



I get lots of interference, or feed over noise whenever I get within two or three miles  of a local radio tower.  

Is there some kind of antenna filter or something I can use to prevent this?

My antenna I believe came off a general aviation,  possibly a Cessna 172.



Any radio experts out there in Kolb land  that can point me in the right direction to fix this?



Gene Z

mdnanwelch7(at)hotmail.co
Guest

Posted: Wed Apr 07, 2010 5:51 pm Post subject: Looking for help to fix radio noise?

Gene,



 



  Can you describe your "ground plane".....the area that your antenna mounts to.



 



  If I'm not mistaken, and I'm no expert, I believe you have to have at least a rectangular metal grid, the length of your antenna in each direction, that the antenna mounts in the center of.



  You can use 1/2" wide copper tape, soldered in the center of a cross, with all 4 arms 23" long.  You then mount the antenna in the center of the cross, making sure you attach the antenna's ground to your "antenna plane".



 



  This is how I understand it.  If we have any antenna gurus, I'm sure they can correct me.  IIRC, Boyd knows some details on electronics and stuff.



 



  Hope I helped,



 



Mike Welch



MkIII

 

[quote] Subject: Looking for help to fix radio noise?

 From: etzimm(at)gmail.com

 Date: Wed, 7 Apr 2010 18:34:36 -0700

 To: kolb-list(at)matronics.com

 

 

 

 Kolb friends,

 

 I have been using an A5 ICOM for several years with an external antenna. It gives me good service in reception and transmitting and I am satisfied with it except for one problem, and I know next to nothing about radio tech.

 

 I get lots of interference, or feed over noise whenever I get within two or three miles of a local radio tower. 

 Is there some kind of antenna filter or something I can use to prevent this?

 My antenna I believe came off a general aviation, possibly a Cessna 172

icrashrc

Joined: 16 Mar 2006
Posts: 247
Location: Mishawaka, In

Posted: Thu Apr 08, 2010 3:18 am Post subject: Re: Looking for help to fix radio noise?

Gene,



Obviously we need more info on the type of coax and antenna you're using but here's my best guess...

To my knowledge picking up a radio or TV station when close to the broadcasting tower means you need a balun in your system. Without one it's actually possible to overload and ruin the input side of the radio, if it's not protected internally. I've attached a file with a good description of what a balun does and how to make one yourself. It was easier than typing it all myself! 



Scott

Antenna Design.pdf

Description:

Download

Filename:

Antenna Design.pdf

Filesize:

1.3 MB

Downloaded:

377 Time(s)

Eugene Zimmerman

Joined: 10 Jan 2006
Posts: 392

Posted: Thu Apr 08, 2010 4:33 am Post subject: Re: Looking for help to fix radio noise?

Scott,



Thank you,

That is precisely the kind of help I was looking for.

 

I will be trying the balun  soon.

pj.ladd(at)btinternet.com
Guest

Posted: Thu Apr 08, 2010 6:09 am Post subject: Looking for help to fix radio noise?

I believe you have to have at least a rectangular  metal grid, the length of your antenna in each direction, that the antenna  mounts in the center of.>>

  

 If an ordinary handheld works fine from a little  `rubber ducky` antenna about 6 inches long why is all this other stuff  required?

  

 info please

  

 Pat

  

  

   [quote][b]

by0ung(at)brigham.net
Guest

Posted: Thu Apr 08, 2010 7:14 am Post subject: Looking for help to fix radio noise?

I get lots of interference, or feed over noise whenever I get within two or

three miles  of a local radio tower.  

Is there some kind of antenna filter or something I can use to prevent this?

My antenna I believe came off a general aviation,  possibly a Cessna 172.



Any radio experts out there in Kolb land  that can point me in the right

direction to fix this?



Gene Z

 	  Quote: 	
		  >>>>>>>>>>>>>>>>>>>>>>>>>


	


More specific information needed.  Radio, coax, antenna, how mounted and

installed.   And I am trusting that you have used an swr meter to make sure

all the components are matched and tuned properly.   Not knowing all the

details here is a few possibilities.   And if the above is not true,,,,

that would be the first things I would do.    NO even if you have done it,

do it again,  things change.



By local radio tower am I to understand it is an am or fm radio tower...

or police / public safety system.    



The basic problem is your radio inability to filter out the signals from the

radio towers.   It could be fixed with a radio with a better filter in the

receiver.     Or you could add a filter.  Adding a filter may be 1/2 the

cost of a new radio.    



For am fm  you could install a high pass filter. Which would attenuate

(reduce the signal strength)  of all the frequencies below the aircraft band



For public safety,,   you could put in a low pass filter



Or for both you could install a band pass filter that would only pass the

aircraft frequencies  and attenuate all below and above.  



Google band pass filter and see what you can find.



The canister filters that I have used are rather large.   2 x 3 x 12 inches.

However you may be able to find some combination of capacitor and inductor

to hook across the antenna lead that would do the same.  Sorry I am not much

help in designing or specifying the parts.



Boyd Young

mkIII

ham radio operator n7wfm



do not archive.

Ok  just read pats reply.    The rubber duck should be tuned by the

manufacture to the proper frequency,  but because of the nature of rubber

duck antennas,  in order to make them short and convenient,  they are a

compromise out of the box.  A full quarter wave antenna  with a ground

plane, or 1/2 wave dipole,  should transmit and receive twice as far,

don't get me completely wrong, the rubber duck may go 50 miles or so

provided it is mounted in such a way that the signal is not blocked by

surrounding structure.

mdnanwelch7(at)hotmail.co
Guest

Posted: Thu Apr 08, 2010 12:19 pm Post subject: Looking for help to fix radio noise?

Pat,

 

  The flexible antenna that is usually found on handheld radios is a compromise, at best.  It is a skinny wire of about 23" or 58.5 cm, or so, coiled up and cast in rubber.  

  In an open environment, it works sufficient to allow for "basic" radio reception.  It is hardly the best antenna, it just happens to be the most practical......for a handheld radio.

  But, in an aircraft structure, which often means lots of metal, it's ability to receive and transmit is significantly diminished.  Therefore, a person might have to resort to better antenna designs to achieve proper reception, if you want to use the handheld radio in an aircraft.

 

  There are several "types" of antennas.  The dipole antenna Scott shared with us is one.  The is also the conventional aircraft mast, and the copper foil antenna (usually for fiberglass airplanes), to name a couple more.  (I made one of these copper foil antennas for my GlaStar.  I avoided the need for a balun by using tri-ax cable)    



  The are many other antenna designs, each fulfilling it's best role in performance and practicality.



 



  As I said before, I'm no antenna expert, but I did play one on tv once.  (I was an electronics and electrical engineering student in college)  



 



  For a radio to perform very well, a ton of factors must be taken into account.  These factors are what an electronics expert could use to design a decent antenna with.



 



Mike Welch



do not archive



 



   



From: pj.ladd(at)btinternet.com

To: kolb-list(at)matronics.com

Subject: Re: Looking for help to fix radio noise?

Date: Thu, 8 Apr 2010 15:05:26 +0100



I believe you have to have at least a rectangular metal grid, the length of your antenna in each direction, that the antenna mounts in the center of.>>

 

If an ordinary handheld works fine from a little `rubber ducky` antenna about 6 inches long why is all this other stuff required?

 

info please

 

Pat

 

 

 		 	   		  

_________________________________________________________________

The New Busy is not the old busy. Search, chat and e-mail from your inbox

pj.ladd(at)btinternet.com
Guest

Posted: Fri Apr 09, 2010 2:25 am Post subject: Looking for help to fix radio noise?

Hi Mike,

 thanks very much.  i am still playing with  mine as I don`t use it a lot. I just used the extension lead supplied with the  radio.(which i bought from John H some years ago) an stuck the rubber ducky on  the end sticking out below the pod. i think it picks up a signal OK until the  engine is run. Then its useless.

 i was thinking more about  shielding from the  engine but perhaps I should investigate further.

 The Eurostar which I previously had a share in had  a hand held wired in but necause it worked perfectly on delivery I never  investigated further.

  

 First flight of the season yesterday. An hour in  perfect weather. Did a timed climb, a Vne dive, and a couple of stalls to get  the figures for my annual permit and then just swanned around enjoying the  glorious Spring countryside.

 Having not flown since last September I have an  excuse for making a bog of the landing. Much too high and had to go round. I had  to do a baulked landing for the permit as well so that was useful.   Unfortunately the engine stopped on my second approach. i took the flap off a  bit smart to extend the glide and just squeaked in over the hedge.

 Engine started again  to taxi in but on  inspection I found a plug lead had become detached. A bungee seems to be  indicated to hold the leads on.

 All part of lifes rich pattern.

  

 Cheers

  

 Pat

   [quote][b]

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Fri Apr 09, 2010 6:38 am Post subject: Looking for help to fix radio noise?

thanks very much.  i am still playing with mine as I don`t use it a lot. I 

just used the extension lead supplied with the radio.(which i bought from 

John H some years ago) an stuck the rubber ducky on the end sticking out 

below the pod. i think it picks up a signal OK until the engine is run. Then 

its useless.

i was thinking more about  shielding from the engine but perhaps I should 

investigate further.



Pat

Patrick/Gang:



Install a 20,000mf capacitor, or there abouts, in the 12VDC wires after the 

regulator/rectifier.  The capacitor will act like a big filter and soak up 

much of the ignition and alternator noise.



john hauck

Titus, Alabama

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

mdnanwelch7(at)hotmail.co
Guest

Posted: Fri Apr 09, 2010 8:09 am Post subject: Looking for help to fix radio noise?

> Install a 20,000mf capacitor, or there abouts, in the 12VDC wires after the 

 	  Quote: 	
		   regulator/rectifier. The capacitor will act like a big filter and soak up 

 much of the ignition and alternator noise.

 

 john hauck

 Titus, Alabama 

  
	


 John,

  

   I've heard of this remedy before ( I think from you a couple of years ago).  Exactly how would a person hook up this capacitor?  IIRC, it hooks up between the + & - posts of the battery, correct?

  

   Aslo, is this something everyone should do (that uses a radio), or do you think only on a "as needed" basis?

  

 Mike Welch

 MkIII



 		 	   		  The New Busy think 9 to 5 is a cute idea. Combine multiple calendars with Hotmail.  Get busy.  [quote][b]

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Fri Apr 09, 2010 8:34 am Post subject: Looking for help to fix radio noise?

I've heard of this remedy before ( I think from you a couple of years 

ago).  Exactly how would a person hook up this capacitor?  IIRC, it hooks up 

between the + & - posts of the battery, correct?



  Aslo, is this something everyone should do (that uses a radio), or do you 

think only on a "as needed" basis?



Mike Welch

MkIII



Mike W/Gang:



Like a lot of things, I learned it by chance.



Put lights on a dirt bike without a battery.  Bought a kit from JC Whitney. 

Kit included a small capacitor (battery replacement).



Wanted to take advantage of the alternator on the 447 on my Firestar, 

remembered the JC Whitney kit and stole the capacitor from the old dirt 

bike.



A year later, during modification and repairs of FS, decided I probably 

didn't really need that capacitor, so I did not reinstall it.  First flight 

I could not use my radio to receive or transmit.  The ignition and 

alternator noise overwhelmed the it.  I reinstalled the capacitor and the 

noise went away.  Additionally, I had to run resisitor plugs (against Rotax 

recommendation not to)(no change in performance or reliability was observed) 

and shield the plug wires and run metal resisitor NGK plug caps.



The capacitor has a + and - terminal.  + goes to the 12VDC positive wire, 

and the - goes to a good ground on the airframe.



john hauck

mkIII

Titus, Alabama

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

ceengland(at)bellsouth.ne
Guest

Posted: Fri Apr 09, 2010 2:43 pm Post subject: Looking for help to fix radio noise?

On 4/9/2010 11:28 AM, John Hauck wrote:

 	  Quote: 	
		   

     I've heard of this remedy before ( I think from you a couple of years

 ago).  Exactly how would a person hook up this capacitor?  IIRC, it hooks up

 between the +&  - posts of the battery, correct?



    Aslo, is this something everyone should do (that uses a radio), or do you

 think only on a "as needed" basis?



 Mike Welch

 MkIII



 Mike W/Gang:



 Like a lot of things, I learned it by chance.



 Put lights on a dirt bike without a battery.  Bought a kit from JC Whitney.

 Kit included a small capacitor (battery replacement).



 Wanted to take advantage of the alternator on the 447 on my Firestar,

 remembered the JC Whitney kit and stole the capacitor from the old dirt

 bike.



 A year later, during modification and repairs of FS, decided I probably

 didn't really need that capacitor, so I did not reinstall it.  First flight

 I could not use my radio to receive or transmit.  The ignition and

 alternator noise overwhelmed the it.  I reinstalled the capacitor and the

 noise went away.  Additionally, I had to run resisitor plugs (against Rotax

 recommendation not to)(no change in performance or reliability was observed)

 and shield the plug wires and run metal resisitor NGK plug caps.



 The capacitor has a + and - terminal.  + goes to the 12VDC positive wire,

 and the - goes to a good ground on the airframe.



 john hauck

 mkIII

 Titus, Alabama

To add to what John told you, if you hook up the capacitor at the 
	


battery it isn't likely to help you much. (The battery itself does a 

pretty good job of filtering noise at its terminals.)



Try putting it as close to the noise generator (typically the alternator 

or generator)  terminals as is reasonably possible. You can add another 

one as close to the radio's power terminals as possible, also, if the 

1st one doesn't do the trick.



Having said all that, it's possible that the radio station's transmitter 

could just be overwhelming your radio's 'front end'. If that's 

happening, think about that HEE HAW TV doctor's advice: "If it hurts 

when you do that, don't do that" (go near the radio transmitter) I know 

that's not much of a solution, but it might end up being the only one 

that's not financially painful.



Charlie

by0ung(at)brigham.net
Guest

Posted: Sun Apr 11, 2010 7:31 am Post subject: Looking for help to fix radio noise?

Aslo, is this something everyone should do (that uses a radio), or do you 

think only on a "as needed" basis?



Mike Welch

MkIII

Yes...   everyone should consider it.  It will smooth out the electrical

noise in the system.   One other thing that  you can do is to take an old

film canister, or pill bottle.   Cut a small piece of tubing that will run

from end to end,  wrap a wire around the tubing, and slide it into the

canister.  This will work as a resistor to voltage spikes by preventing a

spike from going straight through. And when there is a voltage drop, it will

try and keep the electricity flowing more evenly.  A lot of your high end

car stereos will have these installed on the main power lead.  



Boyd Young

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