From: Ronald KA4INM Youvan <firstname.lastname@example.org>
To: Tower Talk <email@example.com>
Date: Saturday, September 21, 2002 6:49 PM
Subject: Re: [Towertalk] Box forSPG and Lightning protectors
>> There are some curious doodads installed on the guys. A clamp
>> around the cable and a colinear pair of cylinders about 10" long,
>> parallel to the cable, and a tad more than the cable diameter away.
>> The cylinders have rounded ends and show evidence of arcing.
> These are "stock bridge dampers' they are the mechanical equivalent
>of an antenna tuner, reflecting energy (of a particular frequency) back
>up the cable when the cable is vibrated, based on the distance from the
>cable end, the thickness of the guy cable and the weight of the lead
>weights. Or if you prefer:
>They change the impedance of the anchor end of the cable.
>They dampen the high frequency vibrations, like a strummed string.
Vibration dampers can be seen more commonly on high-voltage power lines.
Mounted close to the tower ends of the power line conductors and/or on the
overhead ground wires (which run from tower top to tower top), these
dampers, and those on tower guy wires, absorb the wind-induced vibrations of
the conductors, preventing the wires from fatiguing and breaking apart.
Seen from the ground, the power line dampers look like dumbells hung
underneath the wires.
As an aside on the issue of vibration dampening, one might also see metallic
or plastic rectangular _flags_ in the middle of long spans of outdoor
telephone cables. These are spoilers used to prevent the loosely-suspended
telephone cables (vs the high-tension power lines) from _galloping_ under
certain conditions of temperature (hence wire tension) and wind speed.
Without these spoilers the cables will bounce around like a child's
jump-rope in the wind, also causing fatigue and breakage.
> 73 (= Best Regards) de: Ron firstname.lastname@example.org
> 100% LINUX, since July, 1997 SENT Time and Date are UTC
> Visit my HAM Web SITE at: http://www.qsl.net/ka4inm
Gene Smar AD3F
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