28 and 24 MHz Limited
3/4 Wave Delta Loop
(With added modification for 360 degree
Here is a simple and
easy to build antenna in a Delta Loop configeration that should make 10
and 12 meters lots more fun if you have a limited space situation or
you just like the idea of a smaller than normal sized Delta Loop.
Gets lots of DX too and there is a simple modification using one boom and
2 Delta Loops for complete 360 degree coverage!
John tells us how he
did it....read on!
For winter portable DXing up north, I needed a
compact, simple to install antenna for both 10 and 12 meters that offered
directivity and was economical to build.
I decided on a ¾
wavelength delta loop made from PVC pipe, (the backbone), and #14 gauge
I reduced the size of the loop for ease of installation reasons
(not because of space limitations) from previous experience of erecting
antennas when the temperature was forty below!
Using the standard
formula for loops, 1005 divided by frequency in MHz gives us the
one-wavelength design length for a particular band.
should I use for the design frequency when I want to use two different
bands? Easy, just split the frequency difference like this:
minus 24.950= 3.55 MHz divided by 2 gives us 1.78 MHz.
Add 1.78 MHz
to 24.950 (or deduct 1.78 MHz from 28.500) gives us 26.73 MHz "center"
Now take 1005 divided by 26.73 and you get 37.60
feet times .75
(for ¾ wavelength size)= 28.2 feet
Divide that number by 3 to get the length of each side
of the delta loop gives us about 9 feet and 5 inches long each
A balun is not
required but a good antenna tuner is for operating both bands.
be amazed at the performance of this antenna especially for what it costs
Get it up as high as you can and have fun on ten and twelve
I worked a lot of DX from Alaska and the Yukon switching
back and forth using a pair of these wire beauties (one facing north/south
and the other east/west) at only 20 feet in the air! (See mod below for
dual loop version)
that I also used this antenna “indoor” for 2004 ARRL 10 Meter Contest when
I was portable,
( Long Island ,
NY ), from a 3 story brick apartment complex.
Antenna was not in
a perfect delta configuration andduct taped to a
sheet rocked wall on an end apartment unit. It was easy to work a lot of
DX even before and after the contest on 10 &
sure I caused a lot of tvi, hi hi!
P.S. I also used this design,
(cut for 10M), at my Washington state QTH hanging off my tower at about 30
It was a good performer there
"Mod" - Taking it further!
Dual 5/8 Wave Delta
Loops on a single boom for Omni
Let’s take the "28
and 24 MHz Limited Space Delta Loop" design a step further.
want two separate loops in opposite directions sharing the same "boom"
(and don’t mind going from ¾ WL to 5/8 WL) and you only want one simple
support for the antennas for 360 degree coverage. Asking too much? I don’t
The 10 and 12 meter design frequency (ref. above design on
Hamuniverse.com) is 26.73 MHz, therefore 1005 divided by 26.73 gives us
37.6 feet times .63 (5/8 WL)= 23.69 ft.
Call it 24 feet for
simplicity divided by 3 is 8 feet long each leg of one delta loop
Don’t stop here, lets shorten the top legs of each delta
loop (we’re building two, remember?) by 25% to better fit on the shared
boom (or PVC support frame).
The tops of the loops are now 6 feet long,
therefore each side must be 9 feet long to maintain the total length of 24
feet. It’s a bit odd looking but should work just fine according to my
experience with loops.
Each loop will look something like the Side View
drawing in the picture below:
Above Drawings not to
Now, let’s work
on the PVC support frame. It’s basically a "T" like the Bird's Eye
View in the above drawing and includes rope supports from the
top. Each loop is suspended from each "part" of the "T" boom facing
different directions and 90 degrees from the other. Wires are hanging down
towards the ground.....or can be tilted slightly from the "boom" at
an angle to suit your height requirements at your
"Dots" on the boom in
the drawing above are for rope slings to be top supported. Make the
"A" PVC section 6 feet and 2" long and "B" PVC
section about 7 feet and 6 inches long, (for a little added space
between the antennas).
I’d use 1 ¼" PVC Schedule 40 with one "T"
fitting centered on the support.
separate feed lines for each antenna and an antenna switch plus a good
Total price of the dual antennas should be about half
what you’d pay for a good CB vertical provided you have an extra feed line
and antenna switch not in use.
The feeling of accomplishment of
building it yourself will be priceless!
Although I haven’t tried this
design yet, but for those who do, you may want to offset the "T" fitting a
bit more if you experience interaction between the loops. Good luck and
have fun on 10 and 12 meters!
Now you will have a Delta loop for
North/South or East/West coverage depending on how you install the antenna
at the QTH. No matter how it is installed you should get a full 360
73, "Yukon John",
John F. Reisenauer, Jr.
There are several ways to support or suspend this antenna
whether it is a single or double loop. Aside from getting it as high as
possible, you also want to prevent it from twisting or "flying" in windy
Just by chance that you do not have
a way to support the Delta loop from the top, you could find the
center balance point of the "boom" on each style of
antenna in the above article and use that point on the boom for
supporting on top of a PVC mast.
advisable to NOT use a metal mast "inside" the loop. It could
interact with the antenna if used.
THE NEW TAK-tenna
WE REVIEW IT!
Radio's Newest Limited Space HF