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Old October 16th 05, 12:34 PM
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Default The "Almost" Delta Loop Antenna for Limited Space Shortwave Listening (SWL) made from TV 'type' Parts

For One and All,

The "Almost" Delta Loop Antenna for Limited Space Shortwave Listening
(SWL) made from TV 'type' Parts
http://groups.yahoo.com/group/Shortw...a/message/5856

Another TV 'type' Parts Shortwave Listening (SWL) Antenna
that seems to work in Urban High Noise Areas is the 'Almost'
Delta Loop Antenna made from 300 Ohm Twin Lead.

THE "ALMOST" DELTA LOOP ANTENNA:
Delta Loop { Inverted Equilateral Triangle } Antenna.
The Three (3) Sides of the Triangle are all the same
Length : Top = Left = Right

TYPICAL ANTENNA LOCATION :
These are a good limited space Shortwave Listening (SWL)
Antenna that "Fit Well" along side a House when Hung
Under the Eaves using 24 Foot Delta Shape with three
8 Foot Sides

WHY AN "ALMOST" A DELTA LOOP ANTENNA :
Almost because it is not quite a Loop but two Parallel
Opposing Wires in a Loop (Circle-Square-Triangle) Shape.

WIRE ANTENNA ELEMENT AND SIZING :
The Wire Antenna Element is made of 300 Ohm Twin Lead.
The length of the Wire Antenna Element can be relatively
short, as little as 15 Feet = 5 Feet per side; normally
from about 24 Feet = 8 Feet per Side to 36 Feet = 12 feet
per side; or as big and long as 48 - 72 Feet.

WIRING THE TWIN LEAD ANTENNA ELEMENT :
* Match-Up the Ends of the piece of Twin Lead and trim back
about an Inch of two of the Opposite Opposing Ends; these
are your Dead-Ends (Far-Ends and Antenna Tips).
* Next take the 'remaining' two Opposite Opposing Ends
and "Remove" the Insulation from about a Half-Inch from
the End of Each Wire.
* Connect (Solder) One Wire to one of the Matching
Transformer's 300 Ohm Leads; and connect (Solder) the
other Wire to one of the Matching Transformer's 300
Ohm Leads.

RIGGING THE "ALMOST A DELATA [TWIN LEAD} ANTENNA ELEMENT :
Use TV Wiring Stand-Offs (or Cup-Hooks) as the Top Two
Rigging Points (Corners) for the Delta Loop to hang from.
The Weight of the Coax Cable provides the Mechanical
Loading at the Bottom of the Delta Shape for the Loop.
If you want a short wooden stake in the Ground can be
used to hold everything in-place; or a Half-Pound Weight;
or may be both.

ABOUT THE "ALMOST" A DELTA LOOP ANTENNA :
This is actually a Folded Dipole Antenna (Balanced)
with the Arms of the Dipole Circling back on each
other in close approximation; the standard width of
the Twin Lead. A Ground is not required specifically
for this Antenna so the Shack's Ground for the Radios
and equipment as good or as bad as it is the common
Ground for this Antenna's Coax Cable Feed-in-Line.

MATCHING TRANSFORMER :
A 300 Ohm to 75 Ohm Matching Transformer is used between
the 300 Ohm Twin Lead Wire Antenna Element and the 75 Ohm
Coax Cable Feed-in-Line.

COAX CABLE FEED-IN-LINE :
The Feed-in-Line is 75 Ohm Coax Cable RG6 (RG-6) works well.
The Coax Cable 'hangs down' from the Bottom (Apex) of the
Delta Loop.

RESULTS :
This is not a great Shortwave Listening (SWL) Antenna.
However it does do several things for the Shortwave
Listener :
* Can be used in Limited Space like Under the Eaves
of a House or Hung on the Balcony of an Condo/Apartment.
Uses a relatively Small Area with a small Ground Foot Print.
* Gets the Wire Antenna Element OutSide the Building.
* Makes the Wire Antenna Element Longer than the Radio's
Whip Antenna. (24 Feet vice 2-4 Feet)
* Makes the Wire Antenna Element have a Bigger Signal
"Capture Area" than the Radio's very Thin and Short
Whip Antenna. (8 Foot Delta Area vice 1/4" by 2-4 Feet)
* Makes the Wire Antenna Element a Folded Balanced "Dipole"
type Antenna not requiring any additional outside Ground
Rods. A Folded Dipole of this size and shape that is this
close to the ground is an Omni-Directional Antenna and
exhibits some NVIS properties.
* Uses Low Cost TV type Parts which are readily available.
* Easy Do-It-Yourself Antenna Project that can be made
from common TV type Parts.

SOMETHING DIFFERENT - MAKE IT A CAMPING ANTENNA :
Bigger versions 48 to 72 Feet of this 'Almost' a Delta Loop
Antenna can be made and used as a Camping of Day-in-the-Park
Shortwave Antenna (SWL) Antenna and Rigged between two trees.


iane ~ RHF
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