Topband: Wire closeness in two wire Beverage

[Ford Peterson]

N0TT wrote:


> Any flat strapping material will vibrate like 
> > a guitar string in the wind.  
> 
> Ford,
> 
> Use an odd number of supports with "flat strapping material",
> string the line, then go to every other support (insulator) and
> TWIST the line...that will help prevent flapping in the wind...it
> works!
> 
> 73,
> Charlie
> N0TT

I've seen that trick.  I used it a bunch when I was a kid installing 300 ohm feeders on dozens of TV antennas back at the TV shop of Bob-W0KLG's (my SK elmer).  Twisting it clearly helps.  I based my comments on a study I did when I owned a bike rack business a few years ago.  I spent countless hours riding in the back of a Suburban watching binder straps in the wind.  We needed a binder to act as a hold down on campers.  It didn't matter how you twisted, braced, or protected a 'flat' in the wind, it would start to oscillate like a guitar string.  I watched a common binder (1" braided black stuff) wear through the aluminum sheeting on a camper in about 15 miles at 65 MPH.  You could twist it all you wanted and it would still oscillate.  We ended up going to rope tie downs (round profile) and the problem disappeared completely.

The problem with window line is that I've never been able to make it stay in the air very long.  It seems at every spot that it is secured becomes a weak spot for metal fatigue.  There is no doubt that it will work well for a beverage.  I just opted to use PVC supports and cut grooves at 8", 10", and 12" in case I needed to tweak the impedances using spacing.  Each support, with insulators, costs about $5.  There is no doubt you can use other stuff too.  The #14 house wire was $20 a spool (up from $11 last year!  Ah but the gov says no inflation!  Yeah right...) and you can pull it pretty taught--I see virtually no sag over 50'.

Ford-N0FP
ford at cmgate.com