What kind of voltages and currents are present at the ends of dipoles
assuming 100W of RF and the antenna being close to resonant?

Just wondering,

Tom

Tom Sedlack wrote:
What kind of voltages and currents are present at the ends of dipoles
assuming 100W of RF and the antenna being close to resonant?

Just wondering,

Maximum current is in the feeding point, thus minimum at the ends - that's
pretty logical, as the current must flow between something of different
potentials. In case of voltage, zero in the middle of antenna, and
consequently max. at both ends. So, avoid touching the radiator at the ends
;-)

--
Pawe³ Stobiñski
Republic of Poland

Hi!
Maximum current is in the feeding point,
Not always.

Alexander

Alexander Schewelew wrote:

Maximum current is in the feeding point,

Not always.

Always for a center-fed 1/2WL dipole.
--
73, Cecil http://www.qsl.net/w5dxp



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That's why you gotta have a GOOD insulator at the end of a wire antenna.

K9CUN

"Tom Sedlack" wrote in message ...
What kind of voltages and currents are present at the ends of dipoles
assuming 100W of RF and the antenna being close to resonant?

Just wondering,

Tom

The current should be fairly low at the ends. The current max is at
the feedpoint. Just guessing on the voltage, probably about 700 volts
potential at the ends or so...x10 for a KW...Any kind of decent end
insulator should be ok for 100w. Same for a KW too, but you want to
stay away from green tree branches etc, if you run high power. I've
toasted some of those when the branches touched the ends of the
dipole. MK

(Mark Keith) wrote in message . com...
"Tom Sedlack" wrote in message The current max is at
the feedpoint. Just guessing on the voltage, probably about 700 volts
potential at the ends or so...x10 for a KW..
I had an E-mail that stated:


As P=V^2/R it follows V is proportional to the square root of P and
not directly proportional.

I was thinking the voltage for 1 kw would be in direct proportion. But
it seems not. 2100v? Thought I would throw this in. My original quote
may cause confusion. :/ MK

Mark Keith wrote:
I was thinking the voltage for 1 kw would be in direct proportion. But
it seems not. 2100v? Thought I would throw this in. My original quote
may cause confusion. :/ MK

Assuming Reg's value of Z0=600 ohms for the wire in a dipole, the RMS voltage
will be about Sqrt(600*1000) = 775v. The net voltage will be double that
value or 1550v making the peak voltage about 2190 volts.
--
73, Cecil http://www.qsl.net/w5dxp



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Tom Sedlack wrote:
What kind of voltages and currents are present at the ends of dipoles
assuming 100W of RF and the antenna being close to resonant?

Zero current. A voltage estimate would be V^2/600=100w, or V=245V RMS.
The net RMS voltage would be double that value so peak voltage might
be around 700 volts.
--
73, Cecil http://www.qsl.net/w5dxp



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Cec, I'm not altogether happy about the current coming to a sudden stop at
the ends of a dipole.

What's that stuff which clearly flows between the plates of a wide-spaced
capacitor?