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Antennas

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Rick.Beckman(at)atk.com
Guest

Posted: Fri Feb 01, 2008 11:09 am Post subject: Antennas

Hi, All,  

                        I have a question for you who have experience with antennas. How do you check the ohms of an antenna?      

                                                            Rick Beckman  

   

                        Do not archive  

      [quote][b]

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n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Fri Feb 01, 2008 11:50 am Post subject: Re: Antennas

Actually you don't check the ohms because the antenna and ground are NOT

connected. You can check the coax to the antenna. You need an antenna

test set to check see if the antenna is good. A simple check is to just hook

it up, and listen to the radio. Assuming the comm is cut to the correct 

length, and you can hear people talking you are generally going to be

ok. 



The simple check is "xyx tower/unicom, radiocheck please?"



Regards,

Jeff

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bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Fri Feb 01, 2008 3:03 pm Post subject: Antennas

A DC ohmmeter should show an open circuit when connected across a good antenna, but that doesn't guarantee that the antenna is any good. An SWR meter can tell you whether or not the RF energy is being absorbed by the antenna efficiently. Then again, a 50 Ohm resister across the antenna leads will also give a good SWR reading but won't radiate RF energy worth a damn. The real test of how good an antenna is is the hook it up and call up another transceiver for a radio check. There isn't a whole lot to an antenna and not a whole lot that can go wrong with them other than short circuits and bad connections.

On Feb 1, 2008, at 2:06 PM, Beckman, Rick wrote:

 	  Quote: 	
		              Hi, All,

                        I have a question for you who have experience with antennas. How do you check the ohms of an antenna?   

                                                            Rick Beckman





	






 -- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.



 



 [quote][b]

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_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

robertstdenis

Joined: 10 Jan 2006
Posts: 21

Posted: Fri Feb 01, 2008 5:13 pm Post subject: Antennas

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Last edited by robertstdenis on Fri Apr 23, 2010 7:13 pm; edited 1 time in total

Tim Juhl

Joined: 21 Mar 2006
Posts: 488
Location: "Thumb" of Michigan

Posted: Fri Feb 01, 2008 5:24 pm Post subject: Re: Antennas

Rick,

Why do you want to know?  Typically a whip type antenna is designed to work with 50 ohm coax.  The run is so short that RG58 should do the trick just fine.



Tim



do not archive

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bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Fri Feb 01, 2008 6:40 pm Post subject: Antennas

That's true but I assumed he was talking about a comm antenna. A  

quarter wave whip antenna commonly used for the comm radio, ELT or  

transponder is basically a conductor connected to the center pin of  

the coax connector, it has no matching network and will show a DC open  

circuit. A dipole type antenna with an internal balun such as used for  

the VOR receiver or an an amplified GPS antenna, those are a different  

story.  Other types of antennas with matching networks are not often  

used on small aircraft.

On Feb 1, 2008, at 8:04 PM, Rob St Denis wrote:



 	  Quote: 	
		   



 Depending on the matching network used the antenna will in fact show a

 short by design



 On 2/1/08, Bryan Martin <bryanmmartin(at)comcast.net> wrote:

> A DC ohmmeter should show an open circuit when connected across a  

> good

> antenna, but that doesn't guarantee that the antenna is any good. An

> SWR meter can tell you whether or not the RF energy is being absorbed

> by the antenna efficiently. Then again, a 50 Ohm resister across the

> antenna leads will also give a good SWR reading but won't radiate RF

> energy worth a damn. The real test of how good an antenna is is the

> hook it up and call up another transceiver for a radio check. There

> isn't a whole lot to an antenna and not a whole lot that can go wrong

> with them other than short circuits and bad connections.

>

> On Feb 1, 2008, at 2:06 PM, Beckman, Rick wrote:

>

>>            Hi, All,

>>                        I have a question for you who have

>> experience with antennas. How do you check the ohms of an antenna?

>>                                                            Rick

>> Beckman

>>


	


-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.

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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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_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

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