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Tune Around! Topics For
Technicians! |
KL7BOB Field Day
Antenna
The photos in this article show an antenna I made for
field day and erected as a NVIS inverted V. It was used on 5 hf bands
with a tuner. The apex was at 20 feet and the ends were 10 to 15 feet
above ground. We worked 15m, 17m, 20m, 40m, and 80m using an LDG Z100
autotuner and a Kenwood TS 450 transceiver powered by a standalone 12 v
marine battery. The dark pipe is a 4 foot section of fiberglass pipe and
the white pipe and fittings are 3/4" PVC. 3/4 " PVC pipe ~1 foot 3/4" PVC pipe caps 2 ea 3/4" PVC Tee 1 ea 3/16" x 1-1/2" "J" hooks w/ 2nuts 2 ea 3/16" flat washer 4 ea 3/16" lock washers 4 ea PVC cement Cut 2 pieces of 3/4" PVC pipe about 2" long
and one piece about 8" long. Drill a 3/16" hole in the center of each pipe
cap. Insert the threaded end of the J hook into the hole in the pipe cap
and install a flat washer, a lock washer and a nut on the inside and
outside of each pipe cap. Cement a 2" piece of PVC into each side of the T
and cement the 8" piece to the bottom. Cement the pipe caps to the exposed
ends of the PVC nipples making sure the hooks point up.
The legs of the dipole are not critical in length if you use a tuner. I cut mine to be resonant about 3850 (60 feet.) I used 14 ga stranded, insulated copper wire and installed a thimble and ferrule at each end. On one end strip 8" of insulation and on the other strip just enough insulation to install the thimble and ferrule. On the side to be connected to the coax leave the surplus stripped wire extending from the ferrule. Place a piece of heat-shrink tubing over the exposed wire. Place a heat shrink shrouded disconnect onto the end of the wire and crimp it closed. With a heat gun or hair dryer shrink the tubing snugly to the wire. You will need to make two of these legs the same length. Strip about 4" from the end of a desired length of coax and separate the shield from the center conductor. Twist the shield and place a piece of heat shrink tubing over it. Place a heat shrink shrouded connector and crimp it closed. Likewise place a piece of heat shrink tubing over the center insulator of the coax and crimp a connector on the center conductor. Heat the tubing and connectors with a heat gun or hair dryer to complete the job.
14 ga stranded, insulated wire - 2 pieces 60 feet long Cable thimbles 4 ea Ferrules for crimping 4 ea Heat-shrink tubing Heat shrink shrouded male connectors 2 ea Heat shrink shrouded female connectors 2 ea =================================== There are
many variations for this antenna that can quickly be made.
Hook the ends with the pig tail to the J hooks and connect to the coax. You can use any connector you want, I just found the slip connectors locally. A number of variations for this antenna can quickly be
made. The advantage to the antenna is that you can wrap the legs
and coax of the system separately so it is easier to pack. Also by varying
the lengths of the legs you can have a custom antenna by assembling
different components. This is for the "newbies" out there.....As with all homebrew
construction, Experimenting with antennas and their construction is what the fun of antenna building is all about.
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