... 1.5:1 SWR from 14.150 to 14.350 MHz
Plumber's er, Electrician's Delight
20m Vertical Conduit 20m...
... vertical antenna is made from two lengths of
emt conduit. Both are full length, ten feet long,
just as they come from Home Depot or wherever.
One is a 3/4 inch piece, the other is a 1/2 inch piece, ID.
The smaller diameter piece is inserted into the larger
diameter piece so that the overall length is 18 feet.
The two pieces are then bolted together at the overlap
by a simple pair of 1/4 inch nuts and bolts.
To be sure the two pieces of conduit are joined electrically
at the overlap joint, I sanded the conduit, plus ran a piece
of tinned copper braid from one piece to the other.
The 3/4 inch conduit does not fit perfectly into the 1 inch piece,
there is a lot of play. I simply tightened the bolts that join them
till the larger conduit flattened a bit, holding the smaller piece captive.
The base detail photo shows how it's mounted to one leg of a
tin roof open shed. The shed roof is 8 feet by 16 feet, pretty
close to a 20m quarter wave in one direction. The antenna mounts
on one corner, somewhat similar to what is typical for some mobile
vehicle mounts. It probably produces a bit of a larger lobe over
the area with more ground plane, just as it would on an automobile.
The bottom 24 inches of the antenna is covered by a split length
of plastic irrigation pipe. So as the U bolts squeeze the thing
against the metal ground plane, the vertical element remains insulated.
There's probably some capacitive joining going on there, but instead
of worrying about it, I simply hooked it up and measured it
with the MFJ meter.
The 18 foot length was purely a guess/convenience. I made
no attempt to tune it prior or after install.
It measured 1.5:1 or better from 14.150 to 14.350 MHz.
It's 1.1:1 at 14.210..:-)
to the antenna element...
... is totally non-elegant. SO-239 connector
hangs in mid air. 12 AWG insulated wire
runs to driven element and to "ground"
(metal leg of shed).
Below the coax connection, on the tubular
upright leg, you may be able to see a bolt
with a horizontal wire, running toward the
left side of the photo. That wire is a "radial"
of sorts. It's a piece of 17 ga bare aluminum wire
something like 20 feet long.
Genuine DUCT TAPE insulates the shed leg
at the area where the antenna connection
bolt is. The bolt doesn't really touch
the upright grounded tube, neither does
the flattened end of the emt conduit.
But I couldn't resist a chance to add
duct tape to the situation, just in case
winds caused the base of the antenna
to lever over and touch the shed leg.
Needless to say, none of the measurements
nor the construction/engineering practices
are very exacting, calculated, or pretty.
I take this antenna down regularly and take it
with me into the desert, erecting it on my
The white tape fence you see
in some of the photos is hotwire fencing.
We use it to layout horse training obstacles.
By the way, that tape material is incredibly
strong nylon or poly web with very small wires
woven into the material. Seems like it would be
a natural choice for antenna element
The antenna is painted in my standard
"snorkel" camo motif. See the other antennas
on this site for more on how I do that and why.
In the lower right photo, there are TWO vertical
elements. Look closely at the thinner, taller,
curved palm tree trunk on the left. Just to it's
right is the vertical 20m conduit antenna.
Just to the LEFT of the skinny palm tree
is another upright, also painted snorkel camo
pattern. That upright is the (off)center support
for my "Snorkel Antenna" described elsewhere
on this site. It supports my asymmetrical
wire dipole, which is an 80m quarter
on one side, and a 40m quarter on
the other side. You may be able to see
the horizontal wire elements in
the very first photo on this page.
At the very top of this conduit vertical I've mounted a
standard 3/8 inch antenna mount, inside the uppermost tube.
It's not currently in use but I thought I'd experiment with
adding hamsticks or other extensions to the top of this
monster, perhaps making it a top loaded half, 5/8 or
some other "longer than a quarter wave" vertical.
Rapid Deploy Station
Urban Desert Ops
EMT Conduit Antenna
Recycled 2m Yagi
Mil Mobile Base
6m Ground Plane
Return to QTH
The rest of my life?