Frank Alforo wrote:
"But a bird can perch on my antenna wire while I transmit 100 watts and
it stays there seemingly without a care in the world."

Frank isn`t using enough power. I worked in a shortwave broadcasting
plant filled with 50 KW and 100 KW DSB fully modulated transmitters.
Our relatively flat transmission lines were of the 2-wire unshielded
600-ohm variety. These lines must have attracted countless tired
migratory birds to alight or try to alight. When a bird would try to
grasp a wire, it would instantly be consumed in a puff of smoke and
steam. No carcass fell to the earth. Poof! it was gone. Many times their
claws were left behind gripping the wire leaving us a record of the
bird`s visit. Many wires were covered with bird claws. RF can kill more
birds than cats can.

Best regards, Richard Harrison, KB5WZI

On 2006-06-26, Richard Harrison wrote:
bird`s visit. Many wires were covered with bird claws. RF can kill more
birds than cats can.

Maybe we can use this to distract people who claim wind farms are bird
killers.

--
Ben Jackson

http://www.ben.com/

Okay silly question Richard

Did the birdless claws have any noticable effect on the match/tuning of
the antenna?

grin

Cheers Bob

Richard Harrison wrote:
steam. No carcass fell to the earth. Poof! it was gone. Many times their
claws were left behind gripping the wire leaving us a record of the
bird`s visit. Many wires were covered with bird claws. RF can kill more
birds than cats can.

"Frank Alforo" wrote in
:

If I touch the coil in my tuner while transmitting I get a painful rf
burn. But a bird can perch on my antenna wire while I transmit 100
watts and it stays there seemingly without a care in the world. How
come?

The bird is (usually) small compared to the wavelength. Much smaller than
you are. And, except at the ends of antenna elements, the voltage is not
particularly high. Whereas there is a high voltage across your coil and
you are a much larger portion of a wavelength than the bird, so significant
current will flow into you if you touch the coil.


--
Dave Oldridge+
ICQ 1800667

Frank Alforo wrote:

If I touch the coil in my tuner while transmitting I get a painful rf
burn. But a bird can perch on my antenna wire while I transmit 100 watts
and it stays there seemingly without a care in the world. How come?


Frank,

Some basics.

There are two types of RF radiation, Non-ionisation and Ionisation
radiation. The HF bands are non-ionisation ( normally ) and the damage
you'll notice is generated either from High Voltage or RF Radiation.

Look in the ARRL handbook on RF safety. Different parts of the body have
different frequency ranges where we have extra absorption of RF radiation.

Touching a coil in the tuner? This type of RF burns are either primary High
Voltage or secondary = induced or transferred via capacitance to a metallic
object within the antennas RF field.
( Why the F**K do you touch a coil in tour tuner whilst transmitting!? )
Do you put your finger in your cars cooling fan too?


The result is tingling sensations and direct proportional of the power ( or
stupidity ), different Voltages will occur. High Q antennas can have really
nasty voltages, like magnetic loops.

High Voltage gives burns and can give nasty and very deep internal damages.
Read your safety regs! You are supposed to know these regs as a ham!!!

Radiated RF.

Non-ionising RF radiation can be compared to sunlight. To much RF radiation
and your body ( or parts ) will heat up. The effects are like sunstroke or
prolonged exposure to hot climate. Short term effects are nausea and
fainting - like a sunstroke!

A small bird will have problem with RF Radiation but less problem with High
Voltage. unless both poles are present and the stupid bird touches both.
Birds ( as in flying small animals ) have often none or minor problems as a
difference from the other type of birds, that develops to YL's and XYL's...
( No, you are not allowed culling XYL's with RF radiation! )

Ionising radiation is a different matter and is what we normally call
"radioactive radiation". The energy levels of this type of radiation is
much(!) higher than normal RF radiation and if you don't know you are near
areas with this type of radiation, you are either trespassing or plain
stupid....

Generally, higher frequencies, especially in the microwave spectra, tend to
contain high energy levels. Also, bear in mind that the frequency where
water absorbs RF radiation is around 2.4GHz.

If you are inside a high intensity field, get out! One of the first things
to be damaged in a high RF intensity RF field is your eyes. They might
coagulate and I promise - that's a bad thing and most probably
irreversible. The good thing is tho' - you don't need glasses anymore...

Another thing not to do is to place your glutus maximus over a wave tube
with power on --- ********!


Now then....

Most accidents where RF burns and RF radiation exposure occures, creates
damages from a fall, not by the RF radaition itself!

People tend to climb up on ladders and on masts before they decide to get
zapped... Bad idea as most of them fall down and break arms and legs at
the best...

/////


No, I'm not a safety freak but I have a valid certificate for work in masts
and on rooftops where there are aerials...



Cheers All


Dan / M0DFI

Dan Andersson wrote:

( Why the F**K do you touch a coil in tour tuner whilst transmitting!? )
Do you put your finger in your cars cooling fan too?

I reached over to adjust the capacitor not realizing that the set screw that
fixes the capacitor knob onto the capacitor shaft stuck up beyond the
surface of the knob shaft. My finger reached over and touched the end of the
screw as I keyed down.

My free hand was not grabbing a ground wire. I was sitting in an upholstered
chair which was on a rug which was on a wood floor.

And no, I do not put my finger in my car's cooling fan.

Frank A.

"Frank Alforo" wrote in message
...
If I touch the coil in my tuner while transmitting I get a painful rf
burn.
But a bird can perch on my antenna wire while I transmit 100 watts and it
stays there seemingly without a care in the world. How come?

Because the bird is smarter?

west