Roger mentioned his tower gets hit 3 x per yr with lightning. Does any of
the radio gear/coax
ever get fried ? What is getting hit... the top of the tower, top of mast, or
yagi ele's ??
If yagi's are stacked on the mast.. is it always the top yagi that gets hit ?
Does anybody use those porcupine ball things
that extend above the top of the tower. Tall building's in NYC + chicago get
hit all the time with lightning.. and they all have
radio/tv gear on the top floors.... what is their procedure ??
I think it was w3lpl a while back, mentioned the lightning would stop when it
got to his ant farm... pass
right over it.... then start up again on the other side. That apparently will
work... IF the towers are well grnded... and
have lots of well bonded yagi's on the sides of the tower.
Ok, what happens with yagi's like F-12.. where ALL the els are insulated from
the boom ? On a similar
note, F-12 uses a hairpin... so both sides of the DE are bonded....via the
floating hairpin. Both sides of the DE
end up bonded to braid of coax. in this case, you want the coax braid bonded
to top of tower [ and bottom of tower]
On the OWA direct fed yagi's.... no hairpin used... and 1/2 of the DE is not
bonded to top of tower via braid. Now what do you
do? Can you install say a 45 uh choke [ made from 12 ga magnet wire, wound
on single torroid] directly across the ant terminals ?
[ or one side of ant terminal to boom] At least that would DC grnd the center
conductor of the coax.. and that 1/2 of the DE. ICE does
the same thing... but I wouldn't trust their box to be water proof. I use the
ice box inside the house, on a 1/4" thick AL plate.. just inside
the basement.
later......... Jim VE7RF
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|