On Sun, 25 Jun 2006 12:09:18 GMT, Cecil Moore
wrote:

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?

You could probably hang by one hand from a 20 kV power
line and be OK as long as you didn't complete a current
path to another wire or ground.


You could probably hang by both hands if they were close together. I
would not want to try it, though.

When I worked in broadcast radio years ago, I was always amazed that
service personnal would climb the 10 kw tower hot to change lights.
They stated they could feel potential between their hands as they
climbed.

Win, wolz

"Win" wrote
You could probably hang by one hand from a 20 kV power
line and be OK as long as you didn't complete a current
path to another wire or ground.

You could probably hang by both hands if they were close together. I
would not want to try it, though.

When I worked in broadcast radio years ago, I was always amazed that
service personnal would climb the 10 kw tower hot to change lights.
They stated they could feel potential between their hands as they
climbed.
_____________

But the a-c frequency is important here. The voltage gradient between
adjacent hand grips for power in a conductor at AM broadcast station
frequencies (the vertical antenna radiator, in this case) is a lot higher
for the same conducted power than for that same span along a conductor on
the 50/60 Hz a-c power grid.

RF

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.

In article , Win
wrote:

When I worked in broadcast radio years ago, I was always amazed that
service personnal would climb the 10 kw tower hot to change lights.
They stated they could feel potential between their hands as they
climbed.

Win, wolz

Hello, and was that a shunt-fed AM broadcast tower? You might just get
away with a grab at ground level. OTOH, I would think that grabbing onto
a live base-insulated type tower would have serious consequences when
being fed by a 10 kW transmitter. Just looking at the RF bypass hardware
needed at the base to provide for tower lighting (Austin transformer or
Collins lighting choke) should be enough to say "keep away" while
transmitting. Sincerely, and 73s from N4GG0,

John Wood (Code 5550) e-mail:
Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337

In article ,
(J. B. Wood) wrote:

In article , Win
wrote:

When I worked in broadcast radio years ago, I was always amazed that
service personnal would climb the 10 kw tower hot to change lights.
They stated they could feel potential between their hands as they
climbed.

Win, wolz

Hello, and was that a shunt-fed AM broadcast tower? You might just get
away with a grab at ground level. OTOH, I would think that grabbing onto
a live base-insulated type tower would have serious consequences when
being fed by a 10 kW transmitter. Just looking at the RF bypass hardware
needed at the base to provide for tower lighting (Austin transformer or
Collins lighting choke) should be enough to say "keep away" while
transmitting. Sincerely, and 73s from N4GG0,

John Wood (Code 5550) e-mail:

Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337

Then you would be.....wait for it....... WRONG........

"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