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1992-12-27
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3KB
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106 lines
SUBJECT: Wire antennas- part 8
Sloping Vee
The Sloping Vee is basically an Inverted Vee in an equilateral
triangle configuration at a 45 degree angle to the vertical mast.
Not as wideband as the inverted vee and also not omni as the antenna
shows characteristics towards the sloping elements. Basically unity +
in gain. Can be fed with a 50 ohm coax but a 1:1 BALUN is recommended.
Element lengths are similar to the Inverted Vee design.
This antenna is good for AROs with limited space and stay within
a specified area of a band. With a tuner the antenna will cover a
wider range but will be less effective.
Remember that the same hold true for the Sloping Vee as the Inverted
Vee; keep the ends high enough off the ground so that children and
adults can not touch them.
-----------
Terminated Longwires
Similar to the Longwire, the terminated longwire is usually shorter
and terminated with the characteristic impeadance of the antenna. The
terminating resistor should be able to handle at least half the
intended power levels of the transceiver. This terminating resistor
between 500 to 700 ohms when the antenna is 20 - 40 feet above ground.
Similar results can be obtained from the terminated longwire as with
the Longwire as far as antenna patterns, directivity, etc.
------------
Marconi Antenna
The marconi is a quarter wave antenna bent over to be parallel with
the ground. This model works similar to the Folded Marconi except ...
this antenna requires a series LC circuit with the feed line connected
to the inductor as a tap. Let'see how the ascii graphics can handle
this.
---------------------------------------
/
/ Length = 125 for 160m
/
/
|
= tunable cap 700pF
|
}<---0-coax
} L | L = 13 uH
|----|
X gound plane
Well not too bad.
Check out Orr & Cowan for the details.
------------------
Sloper.
This antenna is great for the 'El Cheapo' antenna builders or the
poor guy with no room. The antenna consists of a quarterwave componet
sloping down 45 degrees from the peak of the support and a grounding
lead parallel to the support. The support itself can be used for the
downlead provided it can conduct. The second form of the sloper is
a dipole suspended 45 degrees down from the peak of the support.
In either case, the antenna is directive and the directivity
is as such:
|\ feed point
| \ sloper
| \
| \ ---------> direction of wave
| \
| \
| \
| \
| |
| mast | wooden support
----------------------------------------- ground
If you use a tree for the mast, be sure to clear the branches before
the sloper actually starts. This is the feed point and your down lead
for the ground starts here also. If you look at it, it's nothing more
than a dipole with a vertical ground element and a sloping radiator.
--------------------
In wire antennas part 9 and 10 I will be discussing some of my own
designs and results.
-WS