How to Trouble Shoot Antenna Problems

[rockydoc]

Am having difficulty determining the problem with my radios and intercom diminished performance with altitude and/or distance from ATC and am wanting to verify antenne performance or lack there of.  i.e.  antenna, antenna ground, etc.

Radios were working fine until a radio tech installed an av panel.  Ever since, several other techs have been unable to find the problem even though coax connectors have been replaced.  It seems to be an antenna problem (or cables,, etc. going to the antennae.  How can I verify antennas are working well or not?

Rocky

[Guest]

If the problem is not affecting both radios, switch the antennas, or if you can reach the coax at the back of the radio trays, switch them and repeat your test.

Clarence

[N201MKTurbo]

Well, I was in the radio biz for 10 years as a kid. so some of my advice might be a little dated.

 

Connect the antenna cable where it connects to the antenna to the tech's portable service monitor. Measure the power output and receiver sensitivity at that connection. If it is OK then put a Bird directional wattmeter between that connection and the antenna and measure the output power again and the reflected power. Be sure the extension cable from the Bird to the antenna is more then 1/2 wavelength (about a meter). It should expose any problems.

[rockydoc]

The problem is effecting both radios.  I live in a small town in Mexico where we have no avionics techs and no test equipment.  

[N201MKTurbo]

if you have a handheld, try talking to your plane on the ground. see how far you can drive away and still communicate. compare it with another airplane and see if you have similar performance. If you have a 50 ohm terminator (dummy load) put it on the handheld in place of its antenna, to shorten your driving distance. 

[N201MKTurbo]

Seeing that you are Rocky Doc are you in Puerto Penasco (Rocky Point)?

[rockydoc]

Seeing that you are Rocky Doc are you in Puerto Penasco (Rocky Point)?

Puerto Vallarta

[Piloto]

I use a $39 relative field strength meter that I place over the wing to measure COM power output. It is very effective and easy on checking your COM/Antenna. If you have two COMs compare their signal  strength. Make sure the distance from the antenna is the same for an accurate comparison. 

 

You can get them at  http://www.aesham.com/analyzers/swr-meters/mfj-812b/ 

 

José

[rockydoc]

I use a $39 relative field strength meter that I place over the wing to measure COM power output. It is very effective and easy on checking your COM/Antenna. If you have two COMs compare their signal  strength. Make sure the distance from the antenna is the same for an accurate comparison. 

 

You can get them at  http://www.aesham.com/analyzers/swr-meters/mfj-812b/

 

José

Just called them to place my order.  Since my card billing address is in Mexico and  I want them to ship it to Denver, they aren't certain they'll be able to fill my order.  Said they'd check with the cc company and get back to me.  Thanks for turning me on to this.  Sounds like a piece of equipment that all of us could benefit from having--and at a reasonable price too.

Saludos,

rocky

[rockydoc]

I use a $39 relative field strength meter that I place over the wing to measure COM power output. It is very effective and easy on checking your COM/Antenna. If you have two COMs compare their signal  strength. Make sure the distance from the antenna is the same for an accurate comparison. 

 

You can get them at  http://www.aesham.com/analyzers/swr-meters/mfj-812b/

 

José

they decided to accept my Mexican VISA card and shipped the meter to me today for delivery next week.  Tell me something....what kind of power source does it use?  i.e.  120v, 12v, 9v, AAA, AA, etc., etc.

[Piloto]

Rocky

 

The MFJ does not requires battery or external power. It uses the COM transmitted power for operation. On the back of the unit there is a terminal post where you connect a 20" rigid wire that serves as a whip antenna. For better repeatable measurements use the same location on the wing. I use the filler cap. And the same sensitivity setting. You can use it inside the cockpit while in-flight. A good ref point is on top of the glareshield.

 

José

[rockydoc]

Rocky

 

The MFJ does not requires battery or external power. It uses the COM transmitted power for operation. On the back of the unit there is a terminal post where you connect a 20" rigid wire that serves as a whip antenna. For better repeatable measurements use the same location on the wing. I use the filler cap. And the same sensitivity setting. You can use it inside the cockpit while in-flight. A good ref point is on top of the glareshield.

 

José

Thanks for the details José.  I'm looking forward to learning how to use it.  Muy amable.

Saludos,

Rocky