LA8OKA's Corned Fed Delta Loop
An example of the Corner Fed Delta Loop antenna made for 20 m.
The Delta Loop antenna is one of the famous ”magical
antennas”, but in reality, the Delta Loop antenna is not as magical as it’s
reputation. Despite its reputation as a Multi band antenna, it is a single band
antenna. It can be somewhat tricky to make a Delta Loop with a low SWR. But
after a lot of experimentation I finally found a ratio between the lengths of
the sides of the Delta Loop that give reasonably low SWR into a 50 Ω coaxial
cable almost independent of the high above ground and other surroundings. This
ratio also gives good results no matter orientation, but the antenna have most
gain when Side A is vertical and Side B is horizontal. (See the drawing above.)
This Delta Loop is fed in the corner between Side A and
Side C and can be fed directly with a 50 Ω coaxial cable, but I recommend that
you use a 1:1 balun.
Because of the independence of its surroundings the
Corner Fed Delta Loop is an excellent antenna choice for portable and Field Day
operation.
Important properties of the Corner Fed Delta Loop
antenna:
-
Thicker wire will give higher resonance frequency and
thinner wire will give lower resonance frequency.
-
Higher height above ground will give somewhat higher
resonance frequency and lower height above ground will give somewhat lower
resonance frequency. (This is not a big issue.)
·
It is important to keep the ratio between the Sides. The
angle between Side A and Side B must be 90 degrees.
·
When you have succeeded in building your own Corner Fed Delta
Loop and tuned it for low SWR, the SWR will remain low in almost all
surroundings as long as you keep the ratio’s and angles fixed. (The simplest way
to keep the angles fixed is to keep the angle between Side A and Side B at 90
degrees, and keep the lengths of Side A and B fixed.)
Below is an online calculator which will calculate the
lengths of the sides of the Corner Fed Delta Loop antenna with the correct ratio
between the sides of the antenna.
The only thing you have to do is to enter the operating
frequency of your choice, the diameter of your wire in millimeter and push “ENTER”, and the lengths of the sides will pop up
automatically.
The lengths will be correct for an antenna made for the
20 m band. On higher bands, the resonance frequency will be slightly higher than
the design frequency , and on lower bands, the resonance frequency will be
slightly lower than the design frequency .
EZNEC Files:
If you want to make your own simulations using
EZNEC, you can download my
EZNEC files here:
LA8OKA’s
Vertical Corner Fed Delta Loop
LA8OKA’s
Horizontal Corner Fed Delta Loop
The EZNEC files are made for the demo version of EZNEC v
3.0 who is limited to 20 segments, if you have the full version of EZNEC, I
highly recommend you to add more segments to make the simulation better.
The current distribution on the Corner Fed Delta Loop antenna.
The SWR for the Vertical Corner Fed Delta Loop antenna made for 20 m.
The Far Field Elevation pattern for the Vertical Corner Fed Delta Loop antenna
made for 20 m.
The Far Field Azimuth pattern for the Vertical Corner Fed Delta Loop antenna
made for 20 m.
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This page was last updated
15.05.08
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