In a message dated 6/1/03 6:16:41 PM Eastern Daylight Time, shr@medinaec.com
W0UN writes:
>
> From MY personal experience and comments made by others with similar
> experiences I firmly believe that a naked tower, with or without a
lightning
> rod tends to attract lightning. But that a well grounded tower with lots
> of grounded Yagi elements tends to reduce or virtually eliminate strikes
> in the immediate vicinity. YMMV!
>
MMDNV!
Back in Toronto it really striked me when I upgarded from 65 ft tower with
TH6 to 110' Bertha with 3 el. full size stretched Telrex 40m beam or pair of 62
ft Razors. With old tower I was hit directly and had appliances selectively
burned around the house twice within couple of years. After I put up Bertha
with
big antennas, I was NEVER hit over 10 years. I had 2m Ringo Ranger on the
top, so if I was hit with "overlooked" strike, that thing and connected 2m junk
would have been fried.
Bertha sits in 11' foundation tube with good contact via bearing ring and
(bearing) ball at the base. Before I pored the concrete, I hammered bunch of
water pipes (one came to the surface and I used it to water the grounds before
the
contests :-) into the bottom of the foundation hole and welded them to the
foundation tube. It may be purely luck (statistically should not be) but I was
also "forced" to believe that big antennas "scare" the lightning away and I
join other big antenna nuts in singing the praise for big antennas.
I think what is happening, that tower with large grounded elements beam
serves as a "drainage" capacitor for the immediate semi spherical area, drains
the
charge in vicinity and prevents the formation of the leader and the following
big vaporizing strike. Sort of like an umbrella for lightning effect. While
the pointy bare tower has hardly any capacitance (looking from the top) and
looks "attractive" to lightning for starting the leader and strike. This might
be
the next best thing to do (if can't go high and big), use classic lightning
arrestors and grounding trying to start and create the path for lightning,
rather than letting it hit structures like houses and barns.
Another proof of "umbrella effect" is that when you have static from the
rain, the top antenna is useless, 20 over 9 QRN. Bottom antenna in the stack is
DEAD quiet.
BTW our nasty next door neighbor was once hit twice within 3 minutes and we
got some appliances fried via underground electrical wiring surge (no tower
here). So what we need now is to pass the law requiring hams to have big towers
and antennas and to provide the protection to the neighboring citizens. All
those no antenna communities are horibly exposed to lightning damage.
Yuri, K3BU, VE3BMV
I don't have a degree in lightning sciences and I don't sell antennas (yet
:-)
|