On Tue, 04 May 2004 21:15:40 -0000, Larry W4CSC
wrote:

Gary Schafer wrote in
:

On Tue, 04 May 2004 15:08:08 -0000, Larry W4CSC
wrote:

Your feed point resistance may be 6 ohms but about 5.8 to 5.9 ohms of
that are coil resistance. The radiation resistance of the 15 foot whip
on 3.5 mhz is in the order of .1 ohm.

So about 97% of your power is going up in heat in the coils. Only a
couple percent of the power is making it to the antenna to be
radiated.
Of 650 watts only around 20 watts makes it to the antenna.

A full quarter wave length vertical has a radiation and feed point
resistance of around 36 ohms. Much easier to get power into than a .1
ohm 15 foot antenna.

Oh, don't forget to add in all the ground loss resistance too. Less
power to the antenna yet.

If you can get your feed point resistance down to around 1 ohm then
you will get about 10% of your power into the 15 foot antenna!

Regards
Gary


I've never met anyone so full of pure bull**** in my entire life as you,
Gary. It's simply incredible.

One hopes noone in their right mind will hire you as an engineer and suffer
the consequences.

I doubt 20 watts would make a signal 800 miles away at 20 over S9 in any
conditions, but we're, I'm sure, gonna hear more bull**** from you about it
in the near future.

Larry W4CSC

What class licenses and degrees do you hold, anyways? I've been a 1st
phone licensee since the 1960's, an avid ham operator since 1957 when I was
10 and graduated with honors from many military electronics schools run by
the US Navy because Vietnam's draft kinda got in the way of college in
1964.

Stop by some time and I'll let 20 watts burn your ass for you....(c;
I've never seen 20 watts produce a corona in air over 8" long....
How many kilovolts is that in air at sea level?


What part do you deem to be "bull****" Larry? The parts you don't
understand?

I know that you like sensationalism in big arcs and bragging rights of
running high power. That's fine if that's your thing but you let it
cloud reality. Being able to pull a big arc from an antenna tells you
nothing about its efficiency or how well it will radiate. It does make
for good show though. A tesla coil will produce some pretty high
voltage and corona too.

By the way, time in grade doesn't count either. Being a corporal for
20 years doesn't automatically make one an expert at anything. Not
that you can't be an expert, time in grade just doesn't contribute.

Note that I haven't said that you are full of bull****. I am giving
you the benefit of the doubt.

If you went to tech school as you claim, you have forgotten some of
the basics or you were asleep through many parts.

I would have thought that basic AC circuit theory would have been part
of your education. Maybe not.


If you are interested in how this stuff really works it might help us
to understand some of the things that you have misconceptions about.

Here are a few questions:

1. Do you understand that when you have a capacitor and a coil in
series in an AC circuit that the voltage across either can be much
greater than the applied voltage to the circuit? (basic AC theory)

2. Do you understand that a coil has series resistance as well as
reactance?

3. Do you understand the difference between Radiation resistance and
feed point resistance? This is an important one!

4. Do you know that Radiation resistance is in series with feed point
resistance.

5. Do you know that the same amount of current that flows at the feed
point of the antenna is the same amount that flows in the radiation
resistance of the antenna? They are in series you know.

6. I assume that you know ohms law and that if the same amount of
current flows in two series resistors that the larger resistance will
dissipate more power than the lower value resistor?

7. Do you understand that there is a phase shift between current and
voltage across a coil in an AC circuit.

8. Do you understand that the radiation resistance gets very low in a
short antenna?

If you do not understand any of the above questions please let us
know. That may be the reason that you are not understanding what goes
on in your antenna system.

What I previously wrote pertaining to the voltage developed across the
coil and how low the radiation resistance can be on a short antenna
was quoted directly from the 2000 ARRL handbook. If you have it look
at HF mobile antennas. Page 20.46, 3rd column on the page. It explains
why the voltage is 5000 volts rms across the coil with just 100 watts
applied to an antenna with a radiation resistance of less than an ohm.
Isn't that amazing! Must be black magic huh Larry? Or just maybe it
has something to do with the above questions.

Regards
Gary