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- What follows is a reformulation of the Ohm's
law.His sperimental base is the EH antenna
- invented by Ted Hart, author
of this small tutorial.
- '73 IK5ZPV
I believe the confusion relative to phase can be
simply resolved. Adam said" I contend, as do
all elementary text books regarding AC circuit analysis, that the voltage
measured across a perfect resistor is perfectly "in phase" with the
current flowing through that resistor. Period." You are wrong.
The relative phase relationship between current and
voltage thru and on a resistor can be any value. What the text books say is
that a resistor does not change the phase relative to the current
applied to it. It is the duty of a capacitor and inductor to change the phase of
the current thru them, the capacitor causes the current to lead, the inductor to
lag.
Let me say that again - a resistor does not change
the phase of the current flowing thru it, but it will accept any arbitray phase
of the current relative to the voltage.
This has nothing to do with religion, just basic
theory.
The reason the EH Antenna works with the typical
rice box is that those amplifiers are broadband. They use broadband transformers
to try to get a 50 ohm output impedance, and the output signal remains
in phase with the source resistance developed by the transistors. If you connect
an EH Antenna to a rice box it works well. If you add an antenna tuner, the EH
Antenna will no longer work due to the phase change caused by the tuner.
If your radio properly drives an EH Antenna, at
some frequency it will have a low VSWR. That VSWR increases to a high value as
the transmitter frequency is changed to approach the 3 dB bandwidth frequency.
If you install a series network in the coax line comprised of a capacitor and a
inductor that have equal reactance (series resonance), then adjustment of the
network shifts the phase of the signal applied to the EH Antenna. At any
frequency over the 3 dB bandwidth of the EH Antenna the network can be adjusted
to provide a low VSWR. The series network is simply a phase shift network, and
can be located at the transmitter to effectively remotely tune the EH
Antenna.
This has nothing to do with displacement current -
which is the means used to develop the H field in the antenna.
Is the phase of the signal applied to an EH Antenna
important, or is it just a religious thing? If you want an EH Antenna to work,
feed it with a signal than has the voltage and current in phase. If you only
want a wet noodle, then feed the antenna with any arbitrary phase, and then tell
me the EH Antenna is no good, and you will be right.
Ted W5QJR
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