One of the well-known end-fed ½ λ vertical antennas is the J-Pole. It's ¼ λ stub may be closed and fed at the point of lowest SWR or be kept open and fed at the ends (ARRL Handbook). A closed stub is first choice as it ensures DC ground and static-free operation. The sleeve variant of this is the Sperrtopf Antenna.
Notwithstanding the above, ease of construction prompted homebrewing of an end-fed sleeve antenna with an
open-stub.
OE7OPJ OM Peter's plans for a 'Beer Can Antenna' fitted the bill.
The 19¼" long driven element is cut from a length of 3/16" scrap copper tubing. A 2" diameter aluminium can, 6½" long, is used for the sleeve. Two PVC door buffers with 3/16" bores are used to hold the driven element centrally insulated from the can. One is press-fitted into the mouth and the other fastened with screws to the base of the can. A BNC socket is similarly fixed after it's centre pin is soldered to the driven element pushed out through a hole in the base of the can.
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| 70 cm End-fed Sleeve Antenna |
A tapered bakelite tube and a plastic end-cap complete the picture.
SWR at 435MHz is around 1.5:1.
Related post: A ¾ λ Ground Plane for 70cm
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