Homebrewed Off-Center Fed Dipole
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Revision as of 10:01, 8 April 2012 by Popnokick
Building A Homebrewed Off-Center Fed Dipole Scanner Antenna.
Aluminum/copper tubing construction:
You will need to "press fit" the tubing/"T" connector at the store for proper fit.The tubing/connector is held in place with 2 S/S sheet metal screws for connecting the balun to each element.
Find a "U" bolt to fit your mast.Drill two holes in the support pipe to fit the U bolt.The support pipe is 18" from the "T" to the mast.
Remember,bandwidth increases as diameter of the elements increases. I think,if I remember correctly,at the hardware store,that a few CPVC fittings will fit copper tubing perfectly!
Some say that the 18" element on top mounted works best,Some like the 48" element on top.It does'nt matter,it works the same.
If you use the copper tubing,be sure to paint it with some good,non-conductive paint.I used to paint mine light grey. -Have fun! (Teraycoda)
Variation for Off-Center Fed Dipole Using Simple Wire and 75 to 300 ohm TV Balun Transformer
Electrically, this version is the same as the one using copper tubing (above) but can be assembled quickly and is quite portable. While not as broadbanded as an OCFD using copper tubing or other metal with a larger diameter, the OCFD made from simple wire turns in great receive performance in all the commonly scanned bands, as reported here on RR in multiple message threads.
The legs/ends of the dipole are simple bell wire and shown here coiled up. Uncoil them and hang them vertically; doesn't matter if the long or short leg is at the top... works the same either way. The wire lugs shown at the end of the legs of the dipole antenna should NOT be connected electrically to the wires - just crimp them on over the wire insulation. They are used as convenient hangers for the antenna, and not meant for electrical connection. Obviously, the lugs at the TV transformer/balun ends of the wire should be stripped before crimping on the lugs to ensure contact with the antenna wires. Ensure the 75 ohm coax feedline that you connect from the balun/transformer runs away from the antenna at as near a 90 degree angle as possible.