Double Biquad Antenna
This page contains details on building a
double biquad antenna with approx 13dBi gain.
with a number of biquad antennas (construction details here), I have
found them to be relatively easy to contruct, reliable, and
good performers, with about 11 dBi gain.
A number of
websites showed a variation of the biquad, with the reflector
being double the size, and with the element having twice as
I decided to make a double biquad, to
see how the gain compared to that of a biquad.
I made a double
biquad using exactly the same construction techniques as
described on my Biquad Antenna
Construction page, except the rear reflector is 110x220mm,
and the element is double the size.
Note that the element wires do not
touch where they cross over, but are separated with a gap of
To provide some more
robustness, and to ensure the element doesn't move, I added
some spaces at each end of the element.
The spacers are
made from a small section cut from a hollow reticulation
riser, and attached to the reflector and element using a small
wire tie. Measure and cut the spacers to be 14.5mm long, as
this should result in the element being the correct 15mm from
for the spacers
Drill two small holes in
the reflector, in line with each end of the element. The holes
must be large enough to allow the wire tie to pass through
two holes in the
reflector for the cable tie
are attached by passing the wire tie through one of the holes
in the reflector, through the tube, looped around the element,
and then passed through the tube again, and through the other
hole in the reflector.
The spacers will ensure the
posititioning of the element relative to the reflector will
not change, and also means the antenna is less likely to be
damaged while in transit or while being handled.
Note that you can make spacers out
of any non-metallic material, providing it does not absorb
As with the biquad antenna, if you intend
to use one of these outdoors, I'd recommend you place it into
a weather-proof enclosure, to prevent corrosion, and to
prevent water ingress into the coax.
For information on
connecting a biquad antenna to a wireless radio, have a look
at the page on using
To determine the
difference in gain between a biquad and the double biquad,
some tests were performed, with the signal, noise and SNR
results indicate that the gain of the double biquad is approx
2dBi higher than that of the biquad, which is a significant
As the biquad has a gain of 11-12dBi,
this means the double biquad has a gain of 13-14dBi, so it's a
pretty good performer for something that's relatively easy to
These results are similar to those obtained by
other people who have made double biquads.
that the dBi scale is logarithmic, where 3 dBi is a doubling
in gain. An increase in gain of 2 dBi is equivalent to an
increase of 60%, which is a worthwhile improvement.
Back to ...