In article . com,
RHF wrote:
OK here are a few "Off-Topic" FM & TV Antenna Questions
I have seen two general types of Multi-Element Yagi type TV Antennas
1 - The most common is the Multi-Element Yagi type TV Antenna
with "Flat" Straight-Line Elements.
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2 - The less common is the Multi-Element Yagi type TV Antenna
with slightly "Bent" Canted "Vee" - about 15 Degress Elements.
The Tips of the Elements pointed slightly to the Front of the
Antenna. See the Log Periodic Dipole Array (LPDA) Image
http://www.hdtvprimer.com/ANTENNAS/G...yG.html#logyag
According to a quick skim of my copy of "The ARRL Antenna Book", they're
not Yagi antennas. The key indication that it's a Log Periodic antenna
is the feedline that runs the length of the active elements, zigzagging
back and forth, both sides of a balanced line connecting one element to
the next element down the boom on the opposite side. Ending up with
a shorting stub at the back end. The feedline goes to the front end,
the direction with the most gain.
A lot of these multiband TV antennas are a combination Log Periodic and
Yagi with some unconnected director and reflector elements bolted right
to the boom.
Question : What does the "Canting" of the Antenna Elements Do ?
? Does it Broaden the Angle of Reception {Capture Area}
of the Antenna over the "Flat" Straight-Line Elements ?
? -Or- Does it Narrow the Angle of Reception {Capture Area}
of the Antenna over the "Flat" Straight-Line Elements ?
It converts a LPDA (Log Periodic Dipole Array) to a LPVA (Log Periodic
V Array). This has a higher gain because the elements can then
operate on harmonic frequencies, making more of the antenna work
at the same time. A LDPA only uses a small section of the elements
on any one frequency.
? What about Front to Back (F2B) vice Side Signal Reception ?
* "Flat" Straight-Line Elements -vice "Canted" Elements
? Which has the better Front and less Side Reception ?
? Which has the good Front and fair Side Reception ?
Beats me. Usually higher gain means better directivity.
* * * New Set of Questions * * *
The common Multi-Element Yagi type TV Antenna which
has "Flat" Straight-Line Elements.
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# 1 - When mounted Horizontal "Flat" is very Directional with
a good Front-to-Back Signal and very good attenuation of the
Side Signals.
# 2 -if- It is mounted Vertical {With the Tips Up-and-Down}
it is still some what Directional with a good Front-to-Back
Signal and now has fair Side Signals making it closer to
an Omni-Directional Antenna with some Attenuation of
the Signals coming from the back-end.
Question - Are Both # 1 and # 2 Correct ?
- - - If Not - Why Not ?
This isn't clear here.
Are the elements horizontal or vertical?
Is the boom horizontal or vertical?
If vertical, pointed up or down?
Are the signals you want to receive horizontally (broadcast)
or vertically (police/fire/mobile) polarized.
Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)