need help

[yellowjacket78]

I have a k40 antenna which is mounted via teardrop on top of my truck and I get a lot of vibration as well as humming. How can I get the hummimg out and the vibration down to a minimum?

 

[Robb]

Aerodynamics is the cause? Not sure what a 'teardrop' is- can you explain? Besides vibrations; is it receiving and transmitting OK?

 

[Moleculo]

I think he means a gumdrop mount? The humming could be coming from a lot different things. It could be some electrical noise like alternator, ignition, fuel pump, etc. The vibration could be from the antenna itself. I would try swapping out the antenna with a cheap fiberglass one (or any cheap antenna) and see if the situation improves. If the vibration goes away, you'll know it was a structural problem with the K40. Can you describe the "humming" sound?

 

[yellowjacket78]

yes the humming is coming from the antenna as well. It only does it when I am going between 35 to 45 and after that it stops. No altenator noise in the radio itself. The vibration isn't as bad as the "humming" noise.

 

[Beetle]

Try sliding a tennis ball down the antenna. Find the point at the center of the mechanical vibration and it'll damp the mechanical noise. You need to change the center of mass, somehow.

 

[yellowjacket78]

ok. will the tennis ball reduce the cab noise as well?

 

[W5LZ]

I think you are talking about mechanical harmonics. If so, that tennis ball, or maybe a length of 'ribbon' will change that antenna's "resonance" point to something else, change it's 'tone'.
Don't confuse any of this with how the antenna behaves electrically, it shouldn't affect that at all. The terms used to describe 'resonance', etc, are the same mechanically or electrically (almost).
- 'Doc

 

[yellowjacket78]

ok thanks Doc I understand what you are talking about now