[Antennas] Vibrating hollow elements

[David Robbins]

The cc 4 element 10m has the same problem.  It is probably related to how
easily the relatively short and stiff elements vibrate.   Telrex antennas
(the later models with the lighter and stiffer elements) also had this
problem.  2m antennas probably don't see it because they often have solid
rod elements, and even if done in tubing they would probably not vibrate
much because they would be so short that there wouldn't be much surface area
to set up the vortices that excite the vibration.  The 'fix' is to
mechanically detune the elements and provide a way to dissipate the
vibrational energy by adding a floppy heavy weight inside the elements.  In
larger elements a heavy rope works well, in the small tubing of the 6m
elements I am trying pieces of aircraft cable.  It seems to be working, at
least I am not noticing the vibration as often as I did in the past here.

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
 

> -----Original Message-----
> From: antennas-bounces at mailman.qth.net [mailto:antennas-
> bounces at mailman.qth.net] On Behalf Of W0DXZ at aol.com
> Sent: Wednesday, September 21, 2005 00:30
> To: antennas at mailman.qth.net
> Subject: [Antennas] Vibrating hollow elements
> 
> OK I agree, that the Cushcraft maybe a cheaply made, though  well
> performing,
>  antenna.  Now that mine has fallen apart   (second one to do this) I may
> replace it with another brand, unless CCraft comes  up with a free
> replacement.
> Fat chance.
> So,,, quality antennas, well made, solid elements... anyone  make a solid
> element antenna? I couldnt find any.
> What is the best quality antenna, in the 6 meter 5-6 element  range? Does
> anyone make one that wont vibrate apart? I never had this with a 2M  or
> 10M
> antenna, why 6M?And why the CCraft, just cause there are so many of them?
> I never
> had this problem with my 3 ele CCraft 6M beam.
> Suggestions?
> 
> Bob W0DXZ
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