by Richard Price BSc. MSc.
The main drawback with quad antennas has always been
their complexity (3 dimensional) and difficulty in
assembly/disassembly for portable operation compared to the Yagi.
This design and my development of it have circumvented these
The same design could easily be adapted for use on a regular quad
antenna for portable use on virtually any VHF/UHF frequency. The
secret to the compact folding nature of the antenna is the
combined use of rigid copper elements inter-spaced with flexible
copper braiding. The copper braiding is simply the screen from
RG58 coaxial cable stretched and flattened by hand.
Copper and brass are used, as electrolytic corrosion between the
metals is negligible and brass makes good strong solder
Plate 2. Dismantled and folded Quadruple quad
I used chocolate block
connectors for the 4:1 balun and 2.5m of RG58 coaxial cable for
the feeder reduce losses. The plastic boom is all that is
required to make the whole structure rigid and was made from 2
pieces of 20mm plastic conduit with a joint near the middle. Make
the joint first and then make a notch in one end for the
fibreglass tube to clip in.
Cut to the required length so that when you make another notch in
the other end you have to flex the fibreglass over. Another notch
will need to be made halfway along to clip the middle tube in.
Attachment to a walking pole/mast can be made using whatever
method you prefer.
Fig 2. Horizontal radiation pattern of quadruple quad compared to
a dipole (VHF Communications May 1971).
high gain 70cms antenna for SOTA operation was sought that did
not have the drawbacks of a long Yagi antenna, principally a
narrow beamwidth and bandwidth. This is important as operating
from a hilltop on a relatively under used band requires as broad
a catchment area as possible combined with high gain and a
minimum of turning.
This may be part of the reason behind the low level of use by
SOTA operators. Despite this problem however, 70cms offers
excellent prospects for summit to summit and longer tropospheric
This compact portable antenna for 70cms was developed from an
original design published in VHF Communications May 1971 for
operation on 2m. The Quadruple quad (Plate 1.) is basically four,
closely coupled stacked quad loops, with another four (larger)
loops mounted 1/4 wavelength behind as a reflector. The antenna
has a quoted gain of 11-12db over a dipole and a front to back
ratio of 23db with a very broad (100° approx) frontal lobe
Other very important criteria are the low weight (8oz),
compactness (Plate 2.), speed of assembly (30 seconds) and a good
match into 50 Ohm coaxial cable. After much experimenting
the latter was achieved with a simple delta match feed system
with a 4:1 coaxial balun. This produced an SWR of +/- 1.5
and is quite different to the original article, which used 60W
Once constructed the whole antenna comprises of just 3 pieces to
assemble, a 2-piece split boom providing rigidity for the folding
antenna. Antenna can be mounted for horizontal or vertical
Plate 1. Quadruple quad antenna.
2m x Brass tubing 4mm dia
6m x RG58 coaxial cable
0.75m x 20mm dia plastic conduit
1 x 20mm dia plastic conduit joint
57cm x 8mm dia fibreglass rod/tube
20cm x 14/16swg solid copper wire
24cm x RG174 coaxial cable
Choc block connectors
20 x 3mm brass screws
Spacing between Reflector and Driven element 1/4 wavelength
Driven element (length of brass tube) 17.5cm x 5
Reflector element (length of brass tube) 19.3cm x 5
Spacing between brass rods 1/4 wavelength 17.4cm
Length of braiding required 70cm x 4
4:1 Balun- 1/2 wavelength RG174 =
35cm x 0.66 velocity factor =
Construction of the antenna is quite straightforward. First cut
the brass rods to length. Next cut 3 pieces of fibreglass
rod/tube about 19cm long and drill a 4mm hole each end spaced
17.5cm apart for the brass director and reflector rods to make 3
H shaped structures. Next cut 4 lengths of RG58 coax 70cms long
and strip off the outer jacket and remove the tinned copper
Stretch the braiding and pull between thumb and forefinger to
make a flexible flat strap. Push a brass screw through one end of
the braiding and solder to the end of the brass rod from one of
the H sections.
Measure 17.5 cm along the braiding and attach the next brass rod
and then the next H section and so on. Remember the only
difference between the reflector and driven element is the length
of the brass rods. Note :- The brass rods are allowed to
rotate in the fibreglass and can be prevented from moving from
side to side with a blob of solder on each side of the
||The feed-point was made, by cutting the
centre of the middle driven element brass rod. An insulated
plastic block was inserted and a delta match feed with 4:1 balun
soldered to the element (Fig 2).
Fig 2. Delta match and 4:1 coaxial balun feed (modified from Orr
& Cowan 1990).
On air tests revealed that the antenna is very much
directional and outperformed all my other 70cms antennas except
my 17 element Yagi.
The light weight and compactness means I have no worries about
carrying it around in my rucksack and it can very quickly be
deployed for action.