½ λ End-fed Sleeve Antenna for 70cm

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.

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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Sleeve Dipole Antenna for 2m

The elements for this Sleeve Dipole Antenna are cut from copper tube scrap (3/16" diameter for the driven element and 5/8" for the sleeve).

2m Sleeve Dipole Antenna
The driven element is pushed into a 2" long rubber hose and fitted 1" deep into the sleeve. A tapered bakelite tube gives rigidity to the joint. For an overall length of ½ λ (39" at 145MHz), the sleeve is 19½" long and the driven element 20½".

2m Sleeve Dipole Antenna details
The ends are closed with plastic caps. A BNC socket is mounted on the sleeve end-cap and wired with RG-59/U coaxial cable. The centre conductor is soldered to the driven element and the braid to the sleeve. Care is taken to ensure that the BNC socket does not touch the sleeve.

A good weekend project, awaiting tests for effectiveness.

Related post: Wire Slim Jim for 2m
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Moxon Antenna for 2m

3/8 " aluminium tubular elements, left over from a cannibalised VHF TV Yagi beam, were used to fabricate this 2m Moxon Antenna.

2m Moxon Antenna
Screw joints became a necessity since the elements were not long enough. The ends were flattened and drilled for the purpose.

A scrap plastic handle came in handy for the spacers. It was easy to cut it, drill the fixing holes and make a recess for the BNC socket.

Dimensions were obtained using the 'MoxGen - MOXON Rectangle Generator'.

For vertical polarisation, this antenna is directly mounted on a PVC pipe mast with a screw through each spacer.

Preliminary checks showed that this antenna is as good as, if not better than, my 'simple 2 element array'. Both, being 50Ω antennas, are capable of outperforming even a 3 element array with its associated matching problems.

Related post: Simple 2-element Array for 2m
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Simple 2-element array for 2m

This array was homebrewed using four 18" long telescopic whips and a length of ¾" diameter thick-walled CPVC water pipe.

Data for the 2-element array was obtained from an old ARRL Handbook.

Dimensions in inches: Driven Element - 5540/f MHz, Director - 5263/f MHz, Spacing - 2750/f MHz.

The spacing close to 0.25λ would result in a good match for 50Ω coaxial cable.

Maximum gain would be possible with a director at 0.1λ or a reflector at 0.15λ. However matching issues related to the very low radiation resistance would then have to be tackled (F.C.Judd G2BCX in '2 meter Antenna Handbook').


2m 2-element array
The shorter length of the telescopics was made up with spacers which also served as mounts for the elements. The spacers were made using scrap bakelite strips. Self-tapping screws were used to fasten the elements to the CPVC pipe. A BNC socket was mounted at the feed point and wired to the elements.

2m 2-element array - close-up (element folded)
The array is easy to carry as the elements can be 'telescoped in' and folded. Hence it lends itself to portable operation or direction finding.

Theoretical gain for this array is 3dB.

Preliminary on-the-air checks for gain, front-to-back ratio and null, were encouraging.

Related post: J-Pole Collinear for 2m
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