Crazy George sed:

"At 15', you are in the near field of any HF antenna. You do not want your
station to be in the near field of the antenna. All kinds of undesirable
and often unpredictable things happen."
---------------------------------

Kind of rules out mobile operation.

Of course the metal body of the vehicle probably shields the station from the
effects of the near field.

73 de Jack K9CUN

I would venture to say we all operate in the near field. How does one avoid
it, particularly on 160 meters?

"JDer8745" wrote in message
...
Crazy George sed:

"At 15', you are in the near field of any HF antenna. You do not want
your
station to be in the near field of the antenna. All kinds of undesirable
and often unpredictable things happen."
---------------------------------

Kind of rules out mobile operation.

Of course the metal body of the vehicle probably shields the station from
the
effects of the near field.

73 de Jack K9CUN

On Tue, 6 Jan 2004 13:14:01 -0500, "w4jle" W4JLE(remove this to
wrote:
I would venture to say we all operate in the near field. How does one avoid
it, particularly on 160 meters?

Hi OM,

The greater part of risk is in the wavelength compared to body height.
Sitting down obviously lowers risk.

Now, for the standing individual of average size, that person is
approaching a quarter wave at 10M (especially if you are a fat
conductor). If you were the standard 1 wavelength away from a 100W
transmission, then the standard 22dB down would be your exposure and
you would experience something less of 1 watt of heating throughout
your body. Touch a christmas tree bulb (7.5W) and ask yourself how
uncomfortable that feels, then average that over your 2M² surface
area.

At 160M, you certainly stand the risk of being much closer than 1
wavelength, but you also stand less risk of being a quarter wave tall
(towering egos do not conduct). In any event, you are probably
sitting down anyway. Your radiation resistance in that band makes you
nearly invisible to the power emitted. Those standing next to VOA
half megawatt towers need to check their insurance clauses covering
acts of incipient stupidity.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
Now, for the standing individual of average size, that person is
approaching a quarter wave at 10M ...

Unless the individual is grounded at one end, that 1/4WL is
non-resonant. :-) Richard, what is your velocity factor?
--
73, Cecil http://www.qsl.net/w5dxp



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On Tue, 06 Jan 2004 14:28:06 -0600, Cecil Moore
wrote:
Unless the individual is grounded at one end, that 1/4WL is
non-resonant. :-) Richard, what is your velocity factor?

I can see why you ask about velocity if you are not on ground.

Richard Clark wrote:

On Tue, 06 Jan 2004 14:28:06 -0600, Cecil Moore
wrote:

Unless the individual is grounded at one end, that 1/4WL is
non-resonant. :-) Richard, what is your velocity factor?

I can see why you ask about velocity if you are not on ground.

"On ground" and "at ground potential" are very different things.
I wear thick rubber soles on my shoes forcing a current near-minimum
at each of my ends. And no, my feet are not big enough to cause a
microfarad of capacitance through an inch of rubber.
--
73, Cecil http://www.qsl.net/w5dxp



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On Tue, 06 Jan 2004 14:38:16 -0600, Cecil Moore
wrote:
"On ground" and "at ground potential" are very different things.
I wear thick rubber soles on my shoes forcing a current near-minimum
at each of my ends. And no, my feet are not big enough to cause a
microfarad of capacitance through an inch of rubber.

Are you REALLY that concerned about less than 1W? Perhaps you should
wear Doc Martins.

"Cecil Moore" wrote in message
...
...
...And no, my feet are not big enough to cause a
microfarad of capacitance through an inch of rubber.
-- 73, Cecil http://www.qsl.net/w5dxp


Ahhh! But what about the other end?

The devil made me say this.
Sorry Cecil, just couldn't resist.
Steve K:9:C:I

Cecil Moore wrote:

Richard Clark wrote:

Now, for the standing individual of average size, that person is
approaching a quarter wave at 10M ...


Unless the individual is grounded at one end, that 1/4WL is
non-resonant. :-) Richard, what is your velocity factor?

I don't know about Richard but my velocity factor seriously deteriorated
after age 60 :-)

OOOPPPSSS!! Did I say that :-) Deacon Dave

I thought the same thing until I did some field strength measurements. (a
meter/diode/antenna field strength meter - I have an e-field probe now, but
haven't tried it yet)

Get this:
A 2M quarter wave on the roof has much more field strength than a 5/8 on
the trunk! I saw about 20 dB more. I was also surprised that the same
model car with a sun roof had LOWER inside (with the roof 1/4 wave) than
the one without the sun roof. Go figure.
Steve, K;9;D:C:I

"JDer8745" wrote in message
...
Crazy George sed:
"At 15', you are in the near field of any HF antenna. ...
---------------------------------
Kind of rules out mobile operation.

Of course the metal body of the vehicle probably shields the station from
the
effects of the near field. 73 de Jack K9CUN