Bird Brained Question
 

For the first time in many years, I'm about to put up a 20 meter monobander on
a tower. The XYL is asking questions I cannot answer, specifically relating to
RF and birds. I wouldn't want to be a bird sitting on an element when a KW is
supplied to it? Are my concerns valid?

Gary K5QT

"AA5QT" wrote
For the first time in many years, I'm about to put up a 20 meter
monobander on
a tower. The XYL is asking questions I cannot answer, specifically
relating to
RF and birds. I wouldn't want to be a bird sitting on an element when a
KW is
supplied to it? Are my concerns valid?

Gary K5QT

Your concerns, no. The birds, yes.

I push 1kw out of a 1/2 wave horizontal dipole and the birds never choose it
as a resting place. Down near the ground, it hasn't impeded the population
of several Finch, Cardinal, Northern Thrush and Robin families.

Jack
Virginia Beach, VA

Gary,
Given the number of beam antennas around and how long
they have been up, if it were really a valid consern, there
should be huge flocks of dead birds littering the yards of the
beam owners. The SPCA and the Audubon Society (sp)
SWAT teams would be breaking down doors, etc. It wouldn't
be pretty!
'Doc

AA5QT wrote:
For the first time in many years, I'm about to put up a 20 meter monobander on
a tower. The XYL is asking questions I cannot answer, specifically relating to
RF and birds. I wouldn't want to be a bird sitting on an element when a KW is
supplied to it? Are my concerns valid?

I've tried to chase Starlings away by applying 100W to my 20m rotatable
dipole. Some fly away. Some just sit there and tingle, jumping around
and ruffling their feathers. On my antenna, the only place guaranteed to
chase away a bird is the feedpoint with one foot on each side.
--
73, Cecil http://www.qsl.net/w5dxp



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Maybe get a rent a hawk or the duty owl.

Seriously -- the Ham stores sell a good looking owl to put on towers --
don't if they scare away the other boids -- but they look good (;-)

--
Lamont Cranston

The Shadow Knows
"Cecil Moore" wrote in message
...
AA5QT wrote:
For the first time in many years, I'm about to put up a 20 meter
monobander on
a tower. The XYL is asking questions I cannot answer, specifically
relating to
RF and birds. I wouldn't want to be a bird sitting on an element when a
KW is
supplied to it? Are my concerns valid?

I've tried to chase Starlings away by applying 100W to my 20m rotatable
dipole. Some fly away. Some just sit there and tingle, jumping around
and ruffling their feathers. On my antenna, the only place guaranteed to
chase away a bird is the feedpoint with one foot on each side.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

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


"Cecil Moore" wrote in message
...
AA5QT wrote:
For the first time in many years, I'm about to put up a 20 meter
monobander on
a tower. The XYL is asking questions I cannot answer, specifically
relating to
RF and birds. I wouldn't want to be a bird sitting on an element when a
KW is
supplied to it? Are my concerns valid?

I've tried to chase Starlings away by applying 100W to my 20m rotatable
dipole. Some fly away. Some just sit there and tingle, jumping around
and ruffling their feathers. On my antenna, the only place guaranteed to
chase away a bird is the feedpoint with one foot on each side.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

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



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.

"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."


--
Steve N, K,9;d, c. i My email has no u's.

Birds also sit on high-tension lines carrying many amps at thousands of
volts.
Makes you wonder if it interferes with their built-in compass.

"AA5QT" wrote in message
...
For the first time in many years, I'm about to put up a 20 meter
monobander on
a tower. The XYL is asking questions I cannot answer, specifically
relating to
RF and birds. I wouldn't want to be a bird sitting on an element when a
KW is
supplied to it? Are my concerns valid?

Gary K5QT


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