This is an abbreviated description of the tape measure 3-element 2-meter beam antenna.
This antenna is cheap, and is very tolerant of whacking in the brush during Fox Hunts.
The antenna construction was originally designed by Joe Leggio, WB2HOL
http://home.att.net/%7Ejleggio/projects/rdf/tape_bm.htm.
Reviews of this unusual antenna can be found on EHAM.net
along with a modification for mounting the metal measuring tape.
Parts
1/2 inch schedule 40 PVC
2 cross fittings
1 t-fitting
2 ft of pipe
1-inch steel tape measure minimum of 8 1/2 feet
6 hose clamps stainless steel 1 ½ inch
Electrical tape
RG-58 coax with connector on one end
5-inch piece of copper wire (enameled, stranded, etc)
Figure 1 shows the overall construction. Notice that the driven element is two pieces set up as a dipole and the
reflector and director are single pieces of tape. Variations in attaching the director and reflector elements include
using a washer between the tape and the PVC so that the ridge in the cross piece does not cause the tape to bend or
running the tape inside the fitting and jamming a small ring of PVC into the fitting to secure the tape.
The tape is cut into the following pieces:
Reflector - 41 3/8 inches
Director - 35 1/8 inches
Driven element - 2 sections of 17 3/4 inches
FIGURE 1
Some people like to round the ends that stick out or cover with rubber/plastic cement or cover with electrical tape.
This way, the ends are less likely to cut someone or something.
If you solder the coax and hairpin wire to the driven element, make sure all paint is sanded off and that the tape
has been tinned. Once the tape is on the PVC, the head require to join the solder can melt the PVC pipe. See Figure 2.
FIGURE 2
The PVC pipe sections (7 inches and 11 ½ inches) that join the fittings should cut so that the distance for the center
of each tape is 8 inches between the reflector and driven element and 12 ½ inches between the driven element and the
director.
Many operators put another section of PVC behind the reflector to use as a handle. Attenuators can also be strapped
to the PVC pipe in line with the coax.
The designer claims a cardioid pattern with a less than 2:0 SWR across the entire band and the following predicted
performance figures using YAGI-CAD:
Gain
Front-to-Back Ratio
3 db Beamwidth
3 db Beamwidth
7.3 dBd
greater than 50 db
E = 67.5 degrees
H = 110 degrees
