[Elecraft] Re: Antenna weights

[Charles Greene]

Jerry,

You are overlooking one important factor:  the inertia of the 
weight.  Recall F=MA.  First comes the force, then the acceleration, and 
third the motion.  If the M is considerable, enough Force is needed to 
first accelerate the weight then move it that will break the wire.  The 
spring works on a slightly different principal.  The M is that of the wire 
which is insignificant.  You only tension the wire with the spring so that 
the catenary is the same as it would be without the spring.  Then a sudden 
pull will imedately stretch the spring, the tension is increased only a 
very little, whereas a sudden tension will not move the weight fast enough, 
the tension increases, and it enough, the wire breaks.  My antenna with the 
#22 wire broke with a weight on it.  I added the spring first and it didn't 
break any more, but after that I changed it to #14 wire.  I say that to use 
both is the best approach.

Chas,  W1CG

At 03:33 PM 9/10/2004, wa2dkg at juno.com wrote:
>Weights and springs both work to tension wire antennas...Weights are said
>to have the disadvantage of "rebound", but I have never experienced that
>here in the northeast...Springs increase the tension on the wire
>tremendously as the tree sways and the further the tree sways, the
>greater the tension...This can stretch the wire and exceed the breaking
>point of some element of the antenna assembly...The tension will always
>be the same with a weight, no matter how far the tree sways...For the
>last 4 years I have had a 30 meter dipole up using a 2 gallon plastic
>orange juice container filled with water and anti-freeze...Works for
>me...
>
>Jerry, wa2dkg
>_______________________________________________
>Elecraft mailing list
>Post to: Elecraft at mailman.qth.net
>You must be a subscriber to post to the list.
>Subscriber Info (Addr. Change, sub, unsub etc.): 
>http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/subscribers.htm
>Elecraft web page: http://www.elecraft.com