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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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