Jump to content

Radio problem at one location and orientation only

RobertE

By RobertE
in General Mooney Talk

 Share

Recommended Posts

RobertE Proficient

RobertE

Posted
Posted

When at a particular location with the aircraft oriented a particular way I have almost no ability to broadcast to a particular station. When in other locations I have no problem broadcasting to the same station.

Any idea why this might be true?

chrisk Veteran

chrisk

Posted
Posted

VHF radio waves are not quite line of sight, but close.  My suspicion would be your plane (or external object) is between you radio antenna and the receiving/transmitting antenna.  Jose seems to have lots of experience in this area. Maybe he will weigh in.

RobertE Proficient

RobertE

Posted
  • Author
Posted

VHF radio waves are not quite line of sight, but close.  My suspicion would be your plane (or external object) is between you radio antenna and the receiving/transmitting antenna.  Jose seems to have lots of experience in this area. Maybe he will weigh in.

I should say I never had this problem with another aircraft in the same location/orientation.

N201MKTurbo Grand Master

N201MKTurbo

Posted
Posted

There are quite a few things that can affect the radiation pattern of an antenna. Having nulls and peaks in the azimuth pattern is not that unusual, especially considering the non ideal environment of an aircraft fuselage.

Have you tried the other comm? They are on different antennas and the other antenna likely has a different radiation pattern.

takair Grand Master

takair

Posted
Posted

Where is the antenna mounted? It is likely an installation issue. Sometimes ground plain degrading will cause this type of deterioration. Might be worth pulling the antenna and inspecting for corrosion. Clean up and reinstall. I know bottom mounted antennas can cause this type of issue on the ground. In that case, just use the other radio.

Mooneymite Grand Master

Mooneymite

Posted
Posted

I don't know if this is an associated phenomenon, but I could never receive anything but garbled noise on 120.90 (either radio) when I was in the area of KPDK.  I discussed this with a local tron-head and he looked knowingly, reached into his box of odds and ends and handed me something to install between my ELT and its antenna.

 

I think he whispered "Abra Kadabra" into my avionics access panel, but it might have been "harmonic resonance".  Regardless, it took care of the problem.

 

Tron-heads are weird, but sometimes you just gotta have them perform magic on your plane.

Piloto Grand Master

Piloto

Posted
Posted

When at a particular location with the aircraft oriented a particular way I have almost no ability to broadcast to a particular station. When in other locations I have no problem broadcasting to the same station.

Any idea why this might be true?

This is a common problem with top mounted VHF antennas and low power radios. If you have access to a field strength meter compare the signal levels between COM 1 and COM2. If one is substantially weaker there could be a problem with the antenna cable (high SWR) or the COM transmitter. When experiencing this problem switch to the other COM.

 

On many large aircraft one COM antenna is on top while the other is on the belly. The belly antenna is the one used while in-flight while the top mounted antenna is used on the ground.

 

HF antennas have a similar problem and sometimes you have to change heading for better signal.

 

José 

 Share
Go to topic listing
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.