"Steve Nosko" wrote in message
...

"WB2JKX" wrote in message
...

Chuck wrote in message
...
Woudn't the bird consitute but a tiny capacitance to ground and thus
not
experience an RF burn of consequence?


Let's see here...
First, The bird must have some fundamental capacitance to the rest of the
known universe. lets take a stab and say it is 10pf since he is pretty
far
away from almost everything. I'm sure there is a formula for the
capacitance of a 4 inch diameter sphere somewhere...
Second, Lets model this as 10pf to ground.
Now, what's the current through this 10pf at the tip of the antenna
(assuming his foot-element contact resistance is well below the
Xc)...We're
at 20M, 15M or 10M, so, without resorting to math, Xc is pretty low, in
general terms. Hmmm could be substantial even at 100W, no?
Sounds like his poor feet could indeed get enough to make life difficult.


After all, birds sit on high voltage distribution lines with no ill
effects.
At some point, I guess, corona leakage becomes a factor. You don't see
them
sitting on the 100kv+ stuff.

Completely different situation due to the 60 HZ. The 10pf would lead to
negligible current... "Just don't get one foot on each wire, Son. Your
Unkle Tweety did that and there was a loud pop and he was gone in a bright
flash. Some feathers and a bad smell was all that remained."

"On the other hand, son, getting to the top of one of those really high
man
made trees with wires and your feathers'll all stand on end! Its really
cool! Just don't let your mother catch you doing that."


i havent noticed a problem with injured birds on the broadcast towers. FMs
up to 100,000 W ERP. (about 14,000 W per bay in my case).
5,000 W AM towers both non and directional including top loaded arrays. not
a problem either (in fact i have had birds nest in them)

I have one site that uses open wire transmission lines to feed a 5 tower
array... 10.4 amps of RF at the common point. up to 10 amps of base current.
located in a wildlife refuge. still no birds frying themselves.

now i have been burnt a few times working on this thing... maybe it goes to
show that birds ARE smarter then radio engineers.