My crutches are sold by Walgreens (Item 276734) for
around $46. However, I have found that crutches must be
surplus for a lot of other people. Since starting this project,
I have seen several sets at flea markets for around $2.
That’s definitely the place to buy this antenna hardware.
I found the bottom (foot) of each crutch was almost
the perfect size for a slip-fit inside 3/4 inch ASTM D 2241
PVC pipe. The feet had already been drilled with 1/8 inch
holes. Reaming the holes just a little allowed #8-32 screws
to pass through.
The holes turned out to be perfect for securing the
crutches to the pipe, but the 3/4 inch thin wall PVC
looked a little light for supporting the weight of extended
crutches. A 1-1/2 inch schedule 40 PVC tee and two 3/4-
1-1/2 reducing bushings appeared to be just the right size
for reinforcing the lighter 3/4 inch PVC. Check out Figure
2 and Figure 3.
Home Depot had all the PVC parts and the hardware
in stock for less than $11. Total cost of my project would
have been around $12 if I had bought my crutches at the
Initially, I bought #8-32 x 3 inch machine screws long
enough to pass all the way through the tee, fasten the
crutches, and terminate the RG- 58 coax. As I was drilling
the PVC, I noticed #8-32 nuts would fit in the space
between the crutch foot and the 3/4 inch PVC, so I
decided to drill holes in only one side of the tee and the
short 3/4 inch sleeve. I believe this design provides better
electrical connections and also increases structural rigidity.
I built the antenna (Figure 4) in just over two hours
after I had collected all the materials. The only tools I used
were a hacksaw, screwdriver, drill bit, and pair of long
When the completed antenna was up in the air on
top of a short joint of 1-1/2 inch schedule 40 rigid
conduit, the dipole needed to be shortened to 98 inches
for an SWR of 1.1 from 50 to 51 MHz (Figure 5).
I’m certain this novel antenna would never survive
high winds or ice loads, but it was not built with
permanent installation in mind. I think the best uses for
these crutches are teaching antenna resonance, getting
attention at hamfests, and starting conversations about
emergency communications at public venues promoting
ham radio. NV
Robert Fischer WB8BEL is a physicist and electrical engineer. He
specializes in process instrumentation and maintenance reliability. He
can be reached at BobFischer@Fischer Technical.com.
■ FIGURE 3. ■ FIGURE 2.
1, 5 *
MHz 50.0 50. 5 51.0 51. 5 52.0 52. 5 53.0 53. 5 54.0
■ FIGURE 5.
August 2015 27
■ FIGURE 4.