[Antennas] Delta Loop

[Merv Stump]

Joao, if you like to play with antennas you will love the delta loop.  It is
very forgiving and offers of a host of possibilities, all of which work and
some of which work better than others.  A few points are worth remembering:

1.  Full-wave loops are electrically short so you will want to make it a
little longer than you might think.  I use the formula 1005/F Mhz for total
distance in feet.  Thus for a frequency of 3.6 you will want to make the
antenna a total of 279 feet or approximately 93 feet on a side.

2.  It doesn't need to be an equilateral triangle.  A square, rectangle, or
some triangle other than equilateral will all work.  Almost any figure you
can fit on your property will work, so long as you don't have angles that
are too acute.

3.  Almost any orientation will work.  You can mount it vertically, with the
apex at the top; or vertically with a horizontal section at the top; or you
can mount the whole thing parallel to the ground.  In general, if you mount
it parallel to the ground you will be very strong from 300 to 500 miles out,
but not very strong on long haul dx.  There are exceptions to this and some
dxers have had very good results with the antenna parallel to the ground.
As a rule however, mount it vertically if it is for dx and parallel to the
ground if it is for local work.  Incidentally, I once had one which was
vertically mounted with the horizontal section on top and the apex about 4
feet of the ground, and fed in the middle of the top horizontal section.  By
opening it about a foot at the bottom I had pretty close to a half wave on
160 which worked quite well.

4.  Depending on your environmentals and all of the above the impedance of
the antenna will be somewhere between 50 and 150 ohms at resonance(normally
around 100 ohms).   In any event if you feed it with a 1/4 wave length of 72
ohm coax you will get a match that is certainly close enough.  You can feed
it basically anywhere.  If it is vertically mounted with the apex at the
top, and you feed it 1/4 wave down one side you will get vertical
polarization.  If you feed it in the middle of the bottom section, you will
get horizontal polarization.  However, in my opinion, polarization on 80
meters is pretty much irrelevant,  so feed it wherever you find it most
convenient.

Good luck, and don't be afraid to try anything - it will probably work and
may work really well.

Regards, Merv W2OE