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Alan Shawsmith. V K 4SS
35 Whynol St . West End
Brisbane, Queenslan d. Austra lia
An All B and Curtain Array
1.75 to 30MHz
11 4 " ~flA ,"SPOS E ,. 11' 4 '
17 ' ",'
PHA SE
REVE RS AL
17 ' 4 '
,.
2 9 ' 6 " 00 vet
T!IAfII SPQSE
6 0 0 QHl,l
FEE D
,
TRANSPOSE
Fig. 1 .
D imensions for the all band cur tain arr ay.
Looking for so mething better than a random
length flat top for your multi-band opera
tio n? This pint sized array which puts
o ut a big signal sho uld more than provide the
answer. After so me cut and try trials, the
configura tion sho wn in Fig. I was decided
upon as the best all band result. It represe
nts an attempt to get the most with the
least o utlay. All that is required over a flattop
is some extra wire and insulators. It
should be easily erected o n any average lo t,
as the total length between poles is approximatel
y 11 1 feet. It has su perio r gain over
most fla t-to ps o n 14 , 21 , and 28 Mllz. Its
low a ngle o f radiatio n being o ne feature. If
it is not possible to erect it to its fu ll le ngth,
the 8 fo ot spaci ng at the transpo sed sections
ca n be reduced somewhat with sligh tly less
gain available.
On 1.7 5, and 7 MHz respectively, it really
pe rforms as a quarter, half, and 2 half waves
in phase. However, the co n figu ra tion at 7
MH z does add.some gain and lower the angle
of radiat ion slightly. If DX is desired on
these bands, the bottom wire must be at least
30 feet above ground a nd prefera bl y much
more. For DX o n 14 through 28 Mllz the
bottom wire sho uld be a minimum o f 20 feet
above ea rth. On 28 MHz, there arc some
8 wavelengths o f wire up in space wh ich adds
to the signal.
Maximum radiation is mai nly broadside o n
bands 1.75 through 21 Mllz. It th ro ws the
sha rpes t beam with the most gain on the la t­
ter band, while o n 14 MHz, the pat tern is
broad and somet hing in sha pe li ke a three
leaf clover o n ei ther side o f the axis. No db
measurements have been attemp ted, hut its
performance is far superior to a random
length wire used a t the sa me QTII and strung
at a co m para ble height. Since it is horizontally
polarized, the h igher the array is strung
up, the better.
Being multi-band, no attempt can be made
to match the 600 o h m fecdline. which CJ n be
any length. but ma y have to be pruned if t he
a rray is reticent to acce pt power o n anyone
band . A flexible all ba nd antenna tuner is a
must for proper loading.
... VK4SS
122
73 MAGAZINE