Welcome to Joby's Rhombic Ranch!
I became a Ham in 1978 while still in high school. As I
studied the ARRL Antenna Handbook I learned about the various
types of antennas. I couldn't get excited by dipoles, loops,
yagies, or quads because I wanted one antenna that would
cover many bands and produce a strong signal. The log
periodic qualified on the first account but failed the "Really
BIG Signal" requirement. Then I started reading the
section on long wires. This caught my attention. One antenna
can cover all the bands and if sufficiently large can also
produce a big signal. As I read on through the section I
learned about single long wires, then V beams and finally
Rhombics, I decided that my dream antenna system would
consist of several rhombics pointing in different directions
that I could switch between from the shack.
At the time I had few resources and settled for a couple
of dipoles. It was the high point of the sun spot cycle and I
was working the world just fine. I started college at Texas A&M
that fall, so my dream antenna stayed a dream. After college
I got too busy making a living and went inactive for about 15
years.
Fast forward to 1996. I have been back on the farm for 9
years working constantly between my in town job at the
Electric Coop, clearing land, putting in fields and generally
building the farm into a money making enterprise. That spring
we had one of the most intense dry spells recorded. There was
no hay to cut, no money for new projects, I was left with
little to do.
Out of boredom, I pulled out my old TS 520, tossed a wire
into an oak tree and made a few contacts. I was hooked once
again on ham radio. My Rhombic dream revived, I bought four
35 foot retired wooden poles from the Electric coop, 200 feet
of 450 ohm ladder line and 840 feet of #14 copper weld wire.
I staked the pole positions using 210 foot spans and a 64
degree tilt angle (52 degrees apex angle at the feed point).
The long axis pointed generally to the South West. I assumed
this would give me coverage of Australia and New Zealand to
the South West and Europe to the North East.
Once all the connections had been made, I tuned it up on
20 meters and heard a ham in Georgia calling CQ. I called him
and got a good report. He was running 500 watts into a three
element yagi up about 50 feet. After signing with him, ZK1CC
on South Cook Island called me. My chest swelled with pride
and I remember thinking "Oh yes, I knew it would be like
this!" Since then not every day has gone that well, and
I quickly discovered that the major lobes of this antenna are
quite sharp. New Zealand, and the most southern parts of
Australia boomed in but the central and northern parts of
Australia were not readable. On the reflected lobe that heads
northeast, I discovered Northern Africa, Portugal, Spain, and
southern Italy came in well but England and central Europe
were in a black hole from which no radio waves could escape.
After taking some compass measurements to determine the
direction of the long axis, and using the great circle
bearing and distance finder at http://www.indo.com/distance/
to get precise directions. I concluded that the antenna was
centered on the northern tip of the north island of New
Zealand, and also at Morocco, North Africa on the reflected
lobe. This corresponded to my operating experience. What didn't
make sense was that it also performed very well into Florida
and California. After getting an antenna modeling program I
learned that in addition to the two major lobes, there are
four secondary lobes. This is what the pattern looks like on
20 meters:
The minor lobes are about half the beam width and gain as
the major lobe. So with this one antenna, I got two BIG
signal directions and 4 good signal directions. Everywhere
else signals were very weak.
Amazed with the performance at 27 feet high, I decided to
build several more and point them in other useful directions.
After lots of playing with the great circle direction finder,
I realized that just pointing antennas on the cardinal points
of the compass would not align major lobes in the best
directions. From my place Japan and South America line up
quite nicely. Also central Australia and central Africa
qualified as a must have pair of directions. I used a
computer-mapping program at work to try to come up with ways
to get more antennas for the least number of poles.
After extensive trial and error, I stumbled onto this
design:
By adding 4 poles to the existing ZL-North Africa antenna
I could have 3 more identically sized Rhombics. To my happy
surprise, I discovered that the new antennas would line up
Australia-Central Africa, Japan-South America, and North
south. Now I need a rhombic for Europe. Adding 3 more poles
to the original feed point gives me one more rhombic (the
yellow one) that goes through England, and Germany on its way
to the Middle East. Adding two more poles and sharing the
side support pole that is shared by the blue red and green
provides gain into South Africa, the Caribbean, and northern
Australia to the west. The final design looks like this:
With these 6 Rhombics I have a major lobe going into every
populated part of the world except for central China, This is
what the pattern of each antenna overlaid on each other looks
like on 20 meters:
Note that the secondary lobes tend to fill in the nulls
between the major lobes.
This is a great circle map of the world made by a program
I got from http://hem.passagen.se/sm3gsj/gcm.htm
you just give it your latitude and longitude and it will draw
a map centered on your QTH. The shaded wedges represent the
boundaries of each antenna’s major lobes.
This system is simple to build. Each support consists of a
used 35 foot class 5 wooden pole with a 30 foot section of 2
inch steel pipe overlapping the top of the pole 4 feet. They
are bolted together with two 5/8 inch through bolts. Welded
to the top of the pipe is an eyebolt that has a loop of
dacron rope that runs the length of the pole and pipe.
Once the poles were assembled and the hole positions
staked out, I got a utility contractor to come out with his
digger truck to dig the holes and set the poles.
The feed point support consists of three porcelain
insulators sandwiched between two Plexiglas boards in a
triangle arraignment. One insulator is tied to the support
rope and the other two hold the starting point of either leg
of the #14 copperweld wire. The side supports are insulated
tubing that the copperweld runs through. The support rope is
tied onto a wire that is wrapped tightly around the insulated
tube. The end point is just two porcelain insulators tied in
a V knot to the support rope. Since my 5 Rhombics share
supports, some of the pole/pipes have a second and third
eyebolt 5 and 10 feet down from the top, with two or three
sets of dacron rope supporting different corners of the
different Rhombics. This pole is an example and shows each
type of wire support:
With the supporting insulators tied to their poles at
ground level, I stretch the wire out hand tight and tie it to
the insulators. Next I solder the 450-ohm ladder line to the
feed point wires. Finally I untie the loop of dacron rope
that is running up and down each pole through the eye bolts
at the top. Tie one end of the rope to the support insulators
and use the other end to hoist the antenna into the air the
same way a flag is hoisted up its pole. It takes some walking
back and forth between each pole to get the proper tension on
each support.
At each pole that has a feed point, the ladder line comes
down from the feed point to near the top of the pole where it
is taped to an insulator mounted on a steel rod that was
driven into the pole. This keeps the feed line from flopping
to much in the wind and keeps it from touching the pipe or
pole. At this point the ladder line is connected to a DPDT
relay. When the relay is energized then that rhombic is
connected to the radio. If de-energized, power is sent to the
next feed point relay. This is one of the poles with a relay
box. Note that the control cable is tie wrapped to a support
wire made of #14 galvanized electric fence wire.
Lightning and static electricity buildup is an important
consideration with long wire antennas. To protect the relays
from arcing across the open contacts, I installed a Spark
Plug lightning arrestor between each antenna and its control
relay. I used #6 copper wire to connect the arrestor to a 5/8
inch wide 8 foot long copper clad ground rod driven at the
bottom of each pole with a relay box. There is also one more
lightning arrestor mounted on a ground rod that is bonded to
the utility system ground before the ladderline enters the
house. This bleeds off static from rain, snow, dust, or
nearby thunderstorms, greatly reducing the receiver noise
associated with this type of static. Hopefully this will also
provide some protection from a direct lightning strike.
Impedance matching is a simple matter. Since the antennas
are not resonant on any particular frequency, I just use a 4
to 1 current balun and a PI network antenna tuner. The
uncorrected SWR ranges from 1:1 to more than 10:1 depending
frequency, and length of feed line between the antenna and
transmitter. Transmission losses are minimal, even at 10:1
because of the very low loss characteristics of ladder line.
In most cases, the automatic tuner in my Yaesu 920 can match
any antenna in about 3 seconds. If it can't, I use the
external manual tuner.
This is my "shack", note the antenna relay
control box on top of the antenna tuner. Operation is very
simple. I tune in a station, check which antenna is receiving
the strongest, tune up and give them a call. In pileups,
running 100 watts, about 70% of the time I can get through on
the first or second call. If it takes more than three, I fire
up the home made amp and apply a KW to the wires. It usually
helps
If you have any questions or comments, my Email address is
joby@beecreek.net
Click here to see Ian Cummings excellent rhombic web page.
http://www.mindspring.com/~cummings7/rhombic.html
If you would like to see what my Family and I
look like, click here.
For an explanation of How
Rhombic Antennas Work, click here.
For details on my homemade, 813-tube amp click here. My Homemade 813 Amp
To see my plans for a really big 9 rhombic, 300 ft/leg
system that will cover 17 acres click here. My Future Rhombic Plans
