One Tuesday evening, I was net control for our local ten meter net at 8 PM on 28.330.  After several check-ins, I was told that my signal was down, but steady and readable.  I looked at the VSWR meter and it showed a one-to-one.  I then looked at my antenna switch and knew what was wrong; I was on my 40-meter loop.  I switched to my four-element beam and everyone in the net said I was back to normal.  After several months I checked the delta loop for other bands and it had a three-to-one VSWR on the worst band from 40 meters to 10 meters that I can use.

On ten meters my beam is to the East for the net.  Before net time, I would listen to the South for Florida and Georgia because some of our club members are snowbirds and if the band conditions are good, they check into our net. 

After the 40 meter delta was used on 10 and the VSWR was OK I then decided to build a delta beam for 10 METERS.  I decided to point it to the South, so I only had to switch antennas instead of using net time to rotate my beam.  I used the same design and it worked OK.  I added a reflector and two directors to make it a four-element array.  With my beam pointed to the South, signals were the same on both antennas, but the delta was picking up a wider beam width, so when I moved the one end to another tree to fine tune the direction I added two more directors and the beam width was narrowed enough for what I wanted.  Now I do not have to rotate my beam all the time during the net. 

The cost of my six-element delta beam was only time; since the wire (you can use any size that is on hand) that made up my three-element forty-meter beam was recycled into yet another antenna in the woods.  It is nice to have three acres of tall trees to put my antennas in next to the house.

What I like about the delta loop is, it is fed at the top.  Frequency adjustments can be made on the ground.  I used two pieces of wire 1/2 wave long plus about one foot or more extra on both pieces for adjustments.  After the antenna is tuned up, solder the wires where the adjustment was made.  I use plastic rope to support the antenna.  There is yellow and brown rope; never use yellow in the woods, unless you want it noticed from afar.  Brown blends into the trees and can hardly be seen.  At each element, tie the wire with a knot in the top support rope to hold the spacing in the antenna.  If the rope stretches, don't worry--it will still work, since the spacing is always a compromise.  The lower two corners of the triangle are held out with rope.  Tie the rope around the wire so it will slide for fine adjustments for lowest VSWR.  The radiation pattern seems to be both vertical and horizontal with this design.   

Then I built another delta and pointed it to the east for tests.  Tests with two-element delta and a four-element horizontal Yagi at my QTH, with a four-element Yagi that is on a rotator at W3TO's QTH about twenty air miles to the east of my QTH.  (This test does not take into consideration any feedline losses because the main purpose is a vertical to horizontal signal report test for dual polarity in the delta antenna).
 

My radio is a Kenwood TS870S and Jim's (W3TO) is an ICOM 751A. 

Horizontal Yagi to horizontal Yagi - S9

Horizontal  Yagi to vertical Yagi - S0

Horizontal Yagi to delta - S9

Vertical Yagi to delta - S7

The lowest S meter reading with W3TO's four-element Yagi being rotated and the delta was S3. 

This shows that the delta has an S7 gain and an S3 gain over the Yagi for DX purposes on fadeout conditions, that is caused by polarity change.  The impedance is 50 OHMS and the VSWR is non-existent with the .4 - .2 - .4 isosceles triangle with no matching network.
--Leonard WB3AYW

Add 5% for reflector
Subtract 4% for each director



Tuning notes for lowest swr:
  

Overall length of the driven element can be longer at first than what the chart above shows, then cut in center bottom and the overall length adjusted more or less as needed. Some trial and error may be done here. Twist ends together and solder when done.
Support ropes at bottom corners may also be slid up or down equally to increase or decrease angle at bottom sides. A combination of these procedures will help tune the antenna for lowest swr. 

Editor notes...Since this could be a somewhat complicated antenna to support if multiple elements are used, you may wish to aim it in the general direction of your "most desired direction" and secure it in a fixed position. If you don't have suitable supports for the top and bottom sides, then you will have to modify the supports to suit your needs and location.
If you have the suitable materials and the ability, this would make a very cool multi element beam when used with a rotor or just build the driven element and hang on an inside wall for a great 2 meter emergency antenna or even stealth mode! 

References:
 

Definition: (*isosceles triangle*) A triangle with two equal sides. The angles opposite the equal sides are also equal.

ARRL Antenna Book

Edward M. Noll, 73 Vertical Beam and Triangle Antennas

VE3GEJ, 73 Magazine, June 1972.  "Six elements on twenty meters. pp 17-20

My thanks to W3TO for testing and for the reports from N4WCK in Georgia, WA3PGL and W3AGF in Florida for signal reports, as this antenna was developed and WA3HDK for his support.