Saturday, October 1, 2011



Do you want a full wave loop for 80 and 40 meters but have only a city lot?
Got a 64 foot tower or equivilant support with enough space at the top to add some insulators and a little time plus some wire? Got some 16 foot supports for each end? Want a great signal on both bands?
Then try this antenna project submitted by Mike Wigle, VE6VIS and prepare for loads of fun!

This antenna is the result of many hours of thinking and tweeking and trial and error and starting again and again. It was worth all the effort as I have come up with a very fine antenna that should make the lives of many hams much better by using a loop antenna instead of the inverted V's that so many of us use now.
The antenna is basically a full wave 80 meter loop on top and a 40 meter loop on the bottom all supported from a 64 foot center support, namely my tower. They are both fed from the center feed point with one length of 50 ohm coax. No tuner is required. Use the standard formula: 1005/freqmhz, (your center frequency), for total length of each "loop". Adjust for best swr by raising or lowering feed point from top of antenna. It requires the 64 foot center support (tower or mast) and 2, 16 foot end supports. VE6VIS
Editors note:
Another way of looking at this project is that two Delta loops, one for each band and squashed to fit the space on the tower and your lot are paralleled and fed with one length of coax.

Next we pull the ends of the folded dipole and separate
the middle as in the drawing above.
This allows us to install the antenna in a city lot and still
keep the overall performance of a full wave loop antenna!

Then we add the 40 meter ZZ loop under the 80 and we have the ZZ Wave Net, a dual 40 & 80 meter full wave loop antenna!

Below is how it looks installed on a 64 foot tower with 16 foot
end supports on your city lot.

(80 meter on top, 40 meter on bottom)

80 meter apex to end 70 feet
80 meter end to feedpoint 65 feet
40 meter feedpoint to end 36 feet
40 meter end to bottom 34 feet

Apex to feedpoint 24 feet
Feedpoint to bottom 12 feet

Feedpoint is 4:1 balun
Both loops feed from this point

End support to end support 105 feet

Measure wire and lay out at base of tower.
Attach 1 litre bottle half full of water to the bottom wire about 12 feet from the ends on both sides of antenna.This is so the wires don't twist and so the antenna will have greater tuning range.
Attach apex of antenna to top of tower on a standoff and preferably with a rope and pulley system.
Pull feedpoint up to 24 feet below apex.
Pull ends out to look like the picture.

Tuning Instructions
The wire length is the first thing to get right.
Use the usual method of (low longer) ie: if the swr is higher on the low freq then make the antenna longer and if the swr is higher on the high side then make the antenna shorter.
Then the next step is the distance between the wires.
The distance between the feed point and the apex is 24 feet @ 80 meters.
The final tuning is done by tightening the wires from the ends.

So you get the antenna pulled out to look like the picture above, then you can adjust the swr by tightening and loosening the wires. You will see a great range of tuning here which is why this antenna design is so easy to tune.

The best way to do this is to mark the place where the rope meets the tie off point. ( this is the trick for tuning this antenna) So, if for instance you have the rope tied off to a tree. You mark the point where the rope meets the tree by tying a piece of string onto the rope.
This is your marker.

Check the swr. Then loosen the rope so the marker is about a foot from the tree, Then check the match again. You will notice that it has changed. Now you can tune to a
point where the match is lowest.
Shorten and lengthen the wire to provide the lowest swr within the range that you can loosen and tighten the wires for lowest swr and you will find that this antenna will
match right down flat at the operating freq of your choice :)
Also you may find that the antenna wants to be shorter than the normal calculation.This depends on a number of factors like reflections and hieght above ground.

Tune the 80 meter length first and then the 40. This antenna also works as an 80 and 20 or 80 stand alone, 40 stand alone, 40 and 20 etc.

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