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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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

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.

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

I don't understand why you say this. In the near field the E to I ratio
just isn't at 377 ohms yet, so you can have either a higher E or H field.
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. You do not want
your
station to be in the near field of the antenna. All kinds of undesirable
and often unpredictable things happen."
---------------------------------

"Mike" wrote in message ...
Hi Kevin,

If you have to cut bits off the coax to get the SWR down, your aerial isn't
resonant on the frequency being used. The coax is acting like part of the
aerial.
Get the aerial resonant and it doesn't matter what length of coax you use as
the SWR will not change.


This would be true assuming the transmission line is truly 50
ohms. It almost never really is.

I've asked this question before, and i got similar answers. The
point about losses in long lines improving the SWR are true of course.

But my point is that even if the antenna is a true 50 + 0j, if the
coax is not a true 50 ohms, and is more like 55 or 45 ohms, then the
length of the
coax WILL matter, in terms of the measured SWR.


Slick

"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

"Dr. Slick" wrote in message
om...
"Mike" wrote in message
...
Hi Kevin,
If you have to cut bits off the coax to get the SWR down, your aerial
isn't
resonant on the frequency being used. The coax is acting like part of
the
aerial.
Get the aerial resonant and it doesn't matter what length of coax you
use as
the SWR will not change.


This would be true assuming the transmission line is truly 50
ohms. It almost never really is.
I've asked this question before, and i got similar answers. The
point about losses in long lines improving the SWR are true of course.
But my point is that even if the antenna is a true 50 + 0j, if the
coax is not a true 50 ohms, and is more like 55 or 45 ohms, then the
length of the
coax WILL matter, in terms of the measured SWR.
Slick

So if I get the set up:
We have a 50 ohm load (antenna) and a non-50 ohm line with a 50 ohm SWR
measuring device.

With this, the "LINE SWR" is still unchanged with line length, but the
impedance seen by the SWR meter will change with coax length. It will vary
around the Zo of the line per the Smith chart. So.... It will show a
varying SWR on this meter. The non-50 ohm like could be considered a
matching transformer, but it won't be matching what we want.

However, with a 55 or 45 ohm line this is all moot - in the noise as far
as being significant to worry about and won't mean anything in practice.


Steve K;9;d;c;i

Where is the transmission line on which the SWR is measured by the meter?

Reg wrote,

Where is the transmission line on which the SWR is measured by the meter?


Allow me to sell you some.