Hi Jim,
Thanks for the correction. OMG what a mess. Polarity appeared
everywhere in my text, in my folder names in my links, in my html
heading... I think I got it corrected. Here is the corrected link:
http://tomthompson.com/radio/AntennaPolarization/Antenna%20Polarization%20Measurements.html
Tom W0IVJ
On 6/13/2017 12:09 PM, Jim Brown wrote:
Thanks for the great work, but you're using the wrong word to describe
it. The correct word is "polarization," which describes the
orientation of a field in 3-dimensional space. We most often control
the polarization of a field by the orientation of the antenna that
produces it.
"Polarity" is the positive or negative sense of the waveform. We
change polarity by reversing the pair of wires carrying a signal, or
by passing it through an inverting gain stage. Historically that has
WRONGLY been called "phase." It is NOT phase -- phase is a
continuously variable function and is measured in degrees.
The effects of phase and polarity are VERY different. Phase varies
with frequency, time, and the nature of the electrical circuit
(including antennas) that carry a signal. Phase is defined for a
single frequency. If, for example, we add a length of line to provide
a 180 degree phase shift, the phase shift is different at every
frequency. If, however, we reverse the sense of the signal, the result
is that the two signals cancel at ALL frequencies (provided that the
antenna doesn't also modify the phase, which it often does).
73, Jim K9YC
On Tue,6/13/2017 10:48 AM, Tom Thompson wrote:
Some of you have mentioned in the past about using a tuned loop for
tracking RFI. A question has sometimes arose about the direction of
the null of the loop. Larry Benko, W0QE, and I did some polarity
tests using various orientations of both the transmitting short
dipole and a receiving loop and a receiving short dipole. The results
are shown here:
http://tomthompson.com/radio/Antenna_Polarity/Antenna%20Polarity%20Measurements.html
73, Tom W0IVJ
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