Radio problems above certain RPM

[oregonboy109]

So on todays lesson we were having a strange problem with the radios in the plane. Transmissions at or below 2400 RPM were crystal clear but at 2500 (nearly redline) transmissions could not be understood because the static was so bad. This made upwind and crosswind callouts at the uncontrolled field we were at impossible and we couldn't give position until downwind when we throttled back. Any ideas what might be causing this. My first thought was the vibrations at high rpm might be messing with a connection somewhere but I could be wrong. Plane is a 1979 152-II.
Any thoughts would be much appreciated!

 

[murphey]

Vibrations - almost impossible to resolve on the ground, which is where avionics repairs take place. I had a problem with the DME and the 4th shop finally found the problem of an imperceptable crack in a solder joint. The were the only ones who used a high-power magnifying glass and "wiggled" the board while it was on the shop table.

Might need a filter on alternator. Other than that, I dunno. I do software, not hardware.

 

[kgruber]

You might start by turning the alternator off at the high RPM and see what happens.

 

[SPAJC]

Agree with kgruber...also check any grounds associated with the radio and check the connectors for the antenna. Poor ground will cause these issues as well


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[Capt. Geoffrey Thorpe]

So on todays lesson we were having a strange problem with the radios in the plane. Transmissions at or below 2400 RPM were crystal clear but at 2500 (nearly redline) transmissions could not be understood because the static was so bad. This made upwind and crosswind callouts at the uncontrolled field we were at impossible and we couldn't give position until downwind when we throttled back. Any ideas what might be causing this. My first thought was the vibrations at high rpm might be messing with a connection somewhere but I could be wrong. Plane is a 1979 152-II.
Any thoughts would be much appreciated!

What was the solution?

 

[weirdjim]

So on todays lesson we were having a strange problem with the radios in the plane. Transmissions at or below 2400 RPM were crystal clear but at 2500 (nearly redline) transmissions could not be understood because the static was so bad. This made upwind and crosswind callouts at the uncontrolled field we were at impossible and we couldn't give position until downwind when we throttled back. Any ideas what might be causing this. My first thought was the vibrations at high rpm might be messing with a connection somewhere but I could be wrong. Plane is a 1979 152-II.
Any thoughts would be much appreciated!

Corrections to today's lesson quiz:

"Static" is generally reserved for interference of a sharp, generally random frequent pulsation of noise. Was this distortion or was it truly static? Was it rhythmic at all?

"Radios" implies more than one transceiver. Did this exact thing happen on both radios or was the plural not intended?

At first blush this does sound like a mechanical connection is at fault ... whether it be a true connector problem or the term I've come to know and detest, "bad ground".

Jim