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Author Topic: Singing Mobile Antennas  (Read 1276 times)
KB0CFP
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Posts: 1




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« on: August 11, 2000, 10:02:40 PM »

I have a 2meter 5/8 wave mag and a 10meter mag both on the roof of a 1990 Sedan DeVille.  The problem is that going down the highway these things sing at a most annoying frequency and level.  Operating is not affected but the operator is.  A friend of mine suggested wrapping a piece of tape in around the whip so it forms a flag.  The tape is plaved between 1/2 and 2/3 up the antenna.  I tried it and it didn't work.  I have applied a longer flag to each whip with hopes that will work.

Anyone have any other ideas?



Thanks,


Tim KB0CFP
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KA9ZIM
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Posts: 63




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« Reply #1 on: August 13, 2000, 09:18:02 PM »

I have used quite a few mag mount antennas over the years and have never experienced such a problem. I suppose a whip could create such a sound but I would suspect air passing through something more than around something. Can you give more info about the type of antenna and mag mount you are using. Also, what type of experiments have you conducted if any to try to solve the problem.  I might be able to suggest a couple things but I need more info about your installation first.  
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WA4CNG
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Posts: 33




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« Reply #2 on: August 14, 2000, 11:13:36 PM »

OK, here is the cut to the chase answer.  Wrap the open coil of the whip antenna with tape (black electrical) and it will not s-i-n-g any more.  Open coils are a problem for air-noise issues down the free-way.  I've used this technique on 800Mhz Cellular antennas for the longest time.
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N2FZ
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Posts: 23




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« Reply #3 on: September 03, 2000, 11:41:11 AM »

If the problem is the whip itself that is causing the singing, it might be that the whip is vibrating, similar to a guitar string.   Take a small piece of tubing or rubber sheet and wrap it around the whip and fasten it with tie wraps to dampen the vibration.  It worked with a fibreglas CB whip.
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K8DXX
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Posts: 21




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« Reply #4 on: September 13, 2000, 02:23:42 PM »

I had a similar problem.  It was scary.  I was on my way to work on a cold, dark winter morning.  On top of my 1990 Chevy Lumina, I had a Larsen 5/8 wave mag mount.  It started singing, just this once.  I stopped at a gas station to see if my car was going to blow up.  They couldn't find anything.  So, I started again for work...  more singing.  When I arrived at work, I noticed that there was about 1/4 inch of ice coating the antenna from top to bottom.  Aside from that one time, I've never had the problem again.
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K8YS
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Posts: 79


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« Reply #5 on: September 20, 2000, 11:15:15 PM »

There is another way to stop the singing. Use fine "weed-eater" line and wrap it up the antenna... just a couple twists, you just want to give the antenna an irregular surface. The use heat shrink tube over the entire lenght of the whip.
I had to do this on the broadcast antenna om my old Dodge truck. Worked great.
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KA2QFX
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« Reply #6 on: February 06, 2001, 05:56:57 PM »

I suspect the 2m antenna is doing the singing.  The best way to dampen or eliminate the resonance is to add mass. Try skewering a small foam rubber ball from a toy store on the radiator and see what that does. If that's too obtrusive, maybe you have a few split shot lead sinkers (are you a fisherman?).
You will likely have to play with positioning to find the anti-node. Strike (pluck) the antenna and see where it moves the most.
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