Why?
On 6 Apr, 08:48, (Richard Harrison) wrote:
Art wrote:
"Frankly a lot of people on this net need to get up to speed with
respect to radiation such as tipped antennas ---."
Yesterday`s response seems to have been gobbled in cyber space.
Not all my reference books are over 50 years old. One of my best was
published in 2003 although its principal author was born in 1910. He is
J.D. Kraus, but he had numerous and likely younger collaborators, 6 of
whom are listed as co-authors. The title: "Antennas For All
Applications. 3rd edition".
On page 297 is found an item which illustrates what happens when you tip
an antenna. It is titled: "Antenna Rotation Experiments":
"Consider the radio circuit shown in Fig. 8-74a in which one antenna is
circularly polarized (a turnstile?) and the other is linearly polarized.
If one of the antennas is rotated about its axis a frequency f (r/s),
the received signal is shifted to F + or - f, where F is the transmitter
frequency."
Fig. 8-74 notes:
"Antenna rotation produces amplitude modulation."
Of course it does. When the linear antenna is aligned parallel to one
axis of the CP antenna, the signal is maximum. When the linear antenna
is most misaligned with either axis of the CP antenna, signal is a
minimum. The example demonstrates why polarization alignment, not
tipping or tilt, is usually important.
Best regards, Richard Harrison, KB5WZI
Richard, I couldn't find my Kraus book so I will have to let your
comment go.
I did look in the Jasik book on parasitic elements.
It said"A parrasitic element properly tuned will operate in phase-and-
field relationships
approximating those computed.In multi element arrays, independent
control and phase and amplitude is required and parasitics should be
avoided. However, they may be employed in antennas
designed primarily for power gain" To me this describes a yagi with
parasitic elements designed for power gain regardless of the mix of
polarisation. The Gauss system which does not use parasitics and
therefore pursues the independent control AND PHASE AND AMPLITUDE.
A yagi in a 90 degree multiple of earth does operate in a field
relationship because of its multi phase radiation where as the
gaussion tilts to remove unwanted phase and keeps only the required
phase. This is extremely important in cell transmittions since
channels are only of use when the polarisation is correct and any area
that does not comprise of the correct polarisation results in a
dropped call.
In my last post I mentioned the slope between scanning lines on a T.V.
as a reference line for true polarity. Any comment with respect to the
veracity of that statement since I see a direct corrorally between
that and radiation tilt angles?
Best regards
Art
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