Four Square Antenna
Transcript of Four Square Antenna
EA5AVL Compact 4-Square 40m Antenna - Overview Drawn by MC - 27 Feb 08
Counterpoise
Radials
.
Relay Box
40m
4' 0" (1.5m)
Copper earth
Rod
1/4 wave
Coax
Anchoring point
Perspex
connection
plate
1/4 wave
Coax
1/4 wave
Coax1/4 wave
Coax
N
s
E
W
Capacity Hats
50 Ohm coax
to radio
Antenna select
Control cable
EA5AVL
.
Guy
RopesGuy
Ropes
500pF housed in
plastic box tunes
the 3 reflectors
NOTES
1. The four 1/4 wavelength coax feeds are approx 21' 11'' tip to tip of the PL259 connectors.
2. The four spoke stiff wire Capacity Hats are fitted 12" below the insulators using electrician's terminal blocks.
3. The Relay Box & Capacitor Box are earthed using a 4' 0" copper earth rod close to the mast base.
4. Four 1/4 wave coaxes from relay box to Perspex bottom plates .
5. Four Anchoring points to just stretch out antenna wire e.g heavy brick or long tent peg., (little tension in these wires)
6. The guy ropes are tensioned to support the whole mast.
7. The cross arms can be oriented to any compass bearing to suit personal needs.
40m
COMPACT 4-SQUARE 40 METRE ANTENNA TECHNICAL INFORMATION The antenna has been in use for a number of years, and regularly works amateur radio stations in Japan over the North Pole, Nova Scotia, Alberta, Mexico, Cuba, Uruguay, Columbia, Nigeria, Chad, Perth, and other VK & ZL stations on the short path. It produces excellent 5/9 Reports even during the Sun spot minimum. Further-more the antenna has stood up well to high winds.
Front to Back Gain = 25/30dB
Forward Gain = 5dB
Vertical Polarised
Mono-Band
Power handling = 1Kw +
SWR & Bandwidth 1.5:1 & 700 KHz
SWR 1:1 at centre frequency
No Antenna Matching Unit Required
No rotator required Direction change immediate
Low wind resistance
Scalable for any HF-Band limited only
by the space you have
1/4 Wave Length ( Feet) = 234 / F MHz
6.900 MHz = 33 ft - 11 ins
6.950 MHz = 33ft - 7.0 ins
7.000 MHz = 33 ft - 5.5 ins
7.050 MHz = 33 ft - 2.5 ins
7.100 MHz = 32 ft - 11.5 ins
7.150 MHz = 32 ft - 9.0 ins
7.200 MHz = 32 ft - 6.0 ins
7.250 MHz = 32 ft - 3.0 ins
FINAL VSWR READINGS AFTER TUNING ALL THE ANTENNA ELEMENTS
SWR SWR SWR SWR Frequency
NORTH
EAST
SOUTH
WEST Adjustment
Reqd.
6.900 1.2 :1 1.15 :1 1.1:1 1.15:1
6.905 1.15 :1 1 .1 :1 1:1 1.1:1
7.000 1.1 :1 1:1 1:1 1.1 :1
7.050 1.25 :1 1:1 1.1:1 1.1:1
7.100 1.2 :1 1 .17:1 1.2:1 1.1:1
7.150 1.25 :1 1.2 :1 1.2:1 1.15:1
7.200 1.3 :1 1.25:1 1.25:1 1.17:1
7.250 1.3 :1 1.3:1 1.3:1 1.2:1
7.300 1.3 :1 1.3:1 1.3:1 1.27:1
F-Res 7.000
F-Res 7.000
F-Res 6.975
F-Res 7.000
EA5AVL Compact Four Square Antenna For 40metres - Overview
drawn by MC - 19 Dec 07
Counterpoise
Radials
Notes:
1. The 4 1/4 wavelength coax feeds are approx 21' 11'' tip to tip of the PL259 connectors.
2. The 4 spoke Capacity Hats are made from stiff wire & fitted 12 " below the insulators with electrican's terminal blocks.
3. The Relay Box & Capacitor Box are connected to a 4' 0" copper earth rod at the base of the antenna mast.
4. Four 1/4 wave coaxes from relay box to perspex bottom plates .
5. Four Anchoring points to stretch out antenna wire e.g heavy brick or long tent peg
6. Diagram show the cross arms oriented to NSEW -- but any compass bearing to suit personal needs may be used
.
Rel
ay
Bo
x
G
u
y
R
o
p
e
s
500p
F
tunes
the 3
reflec
tors
1
Met
re
lon
g
Cop
per
eart
h
Rod
Pla
stic
Ca
pac
itor
Box
1/
4
w
av
e
C
o
ax
Anc
hori
ng
poin
t
Pers
pex
con
nect
ion
plat
e
1/
4
w
av
e
C
o
ax
1/
4
w
av
e
C
o
ax
1/4
wa
ve
Co
ax
G
u
y
R
o
p
e
s
Ns
E
W Cap
acit
y
Hat
s
17' 0" 17' 0"
Mast Top
Spreader
Cross
16' 0" arms
North
South
West East
Antenna
Insulator
South Antenna
wire see Note
NOTES
Total wire = 665 Ft or 202 metres
EA
5A
VL
4-
Sq
ua
re 4
0m
An
ten
na
-
Pla
n V
iew
4 off Counterpoise
Radials
each 33' 3" long
4 off Counterpoise
Radials
each 33' 3" long
4 off Counterpoise
Radials
each 33' 3" long
4 off Counterpoise
Radials
each 33' 3" long
1/4
Wavelength
50 Ohm
Coaxes
Perspex Feed
Point Plate
Wing Nut to
connect Radials
Perspex Sheet
Square
4 off CounterpoiseRadialseach 33' 3" long
Wingnut used to fine tune the
antenna wire
SO 239
Connector
Antenna wire
approx 33.25 feetPERSPEX
FEED POINT
PLATE
PLAN VIEW OF ANTENNA SITE
2. All 4 1/4 wave coaxes are cut tolength using the formula
L= 162.3 / F MHz feet.
1. All 4 antenna wires are cut to
length using the formula
L= 234 / F MHz feet.
dra
wn
by M
C -
18 F
eb
08
.
3D elevation
link wire
NO
TE
S
1
. A
ll S
witch
es &
Rela
ys h
ave
bo
th c
on
tacts
wir
ed
in
pa
ralle
l to
im
pro
ve
re
liab
ility
of
op
era
tio
n.
2.
Coa
xe
s t
o th
e a
nte
nn
as e
art
h a
t th
e R
ela
y S
witch
Bo
x, a
nd
are
1/4
wa
ve
len
gth
lo
ng
.
3.
Re
lays 2
Ch
an
ge
Ove
r 1
2 V
olt c
oils
, C
lam
pin
g d
iod
es a
re 1
N10
04
1
00
v 1
A,
Cap
acito
rs 0
.1 M
FD
Dis
c 1
00
V
4.
All
Sw
itch
es a
re h
ea
vy d
uty
to
gg
le s
witch
es. F
or
Co
rre
ct
SW
R O
NL
Y o
ne
An
ten
na
sh
ou
ld b
e s
ele
cte
d 3
re
ma
in R
efle
cto
rs
5.
Refle
cto
r tu
nin
g c
ap
acito
r e
x d
om
estic r
ad
io a
ir-s
pa
ce
d v
ari
ab
le.
6. N
eg
ative
of th
e P
ow
er
su
pp
ly is c
on
ne
cte
d to
th
e c
oa
x b
raid
g
oin
g t
o t
he
an
ten
na
re
lay b
ox
7.
Th
e
sw
itch
es a
nd
re
lays a
re a
ll sh
ow
n in
th
e O
FF
o
r n
on
-op
era
ted
p
ositio
ns.
EA5AVL Compact 4-Square 40m Antenna - CONTROL BOXES CIRCUITS
Drawn by MC - 18 Feb08
DC
Co
ntr
ol
Cab
le
SH
AC
K
Sta
tio
n
Ea
rth
DC
PS
U
+ 1
2.0
/1
3.8
v
Sele
ct
Ante
nna 1
Sele
ct
Ante
nna 2
Sele
ct
Ante
nna 3
Sele
ct
Ante
nna 4
50 O
hm
Co
ax
Se
lec
t N
ort
hS
ele
ct
Eas
tS
ele
ct
So
uth
Se
lec
t W
est
SW
ITC
H B
OX
PL
25
9
-offon
8 t
urn
s
Co
axia
l
Ch
ok
e
AN
TE
NN
A
SIT
E
An
ten
na
1
No
rth
An
ten
na
2 E
ast
An
ten
na
3 S
ou
th
An
ten
na
4
We
st
50 O
hm
Coax
50 O
hm
Coax
50 O
hm
Coax
Rela
y 1
Rela
y 2
Rela
y 3
Rela
y 4
DC
Co
ntr
ol
Cab
le
RL
A /2
RL
B/2
RL
C /2
RL
D /2
1&
2 R
LA
1&
2 R
LB
1&
2 R
LC
1&
2 R
LD
RE
LA
Y B
OX
CA
PA
CIT
OR
BO
X
50 O
hm
Coax
off
offon
on
+
50
Oh
m C
oax
to
TX
via
8-T
urn
Ch
oke
& -
ve
fro
m P
ow
er
Su
pp
ly
NO
TE
S
1.
All
dio
de
s
10
0v 1
Am
p e
.g.
1N
40
01
2.
All
Coil
Cap
acito
rs 0
.1M
FD
Dis
c 3
00
Vw
kg
3.
All
Re
lays 1
2 v
olts 2
C/O
1
00
v /1
A C
on
tacts
4.
Me
tal w
ate
r-p
roo
f b
ox lo
ca
ted
at
ma
st
ba
se
5.
Cap
acito
r in
Pla
stic w
ate
r-p
roo
f b
ox -
wire
s k
ep
t sh
ort
EA5AVL 4- Square 40m Antenna - RELAY BOX WIRING
Drawn by MC - 18 FEB 07
CO
IL
50
Oh
m C
oax
No
rth
An
ten
na
50
Oh
m C
oax
Ea
st
An
ten
na
50
Oh
m C
oax
We
st
An
ten
na
50
Oh
m C
oax
So
uth
An
ten
na
OF
F
ON
OF
F
ON
CO
ILC
OIL
CO
ILC
OIL
4-c
ore
Sw
itc
h B
ox
Co
ntr
ol
Cab
le
to S
wit
ch
ed
+v
e v
olt
s
fro
m R
ad
io S
hac
k
D1
D2
D3
D4
C1
C2
C3
C4
RL
1R
L 2
RL
3R
L 4
NE
WS
Cap
ac
ito
r B
ox
RE
LA
Y B
OX
Off
On
Co
m
Off
On
Co
m
Off
On
Co
m
Off
On
Co
m
se
lec
t
Ns
ele
ct
Es
ele
ct
W
se
lec
t
S
4-C
on
tro
l w
ire
s
To
An
ten
na
Re
lay
Bo
x
Off
On
co
mm
onS
wit
ch
EA5AVL 4-Square 40m Antenna - SWITCH BOX WIRING
Drawn by MC - 18 FEB 07
NO
TE
S
1. S
witch
es a
re h
ea
vy d
uty
DP
DT
( D
ou
ble
Po
le D
ou
ble
Th
row
) i.e
2 x
CH
AN
GE
-OV
ER
2. M
ake
co
nta
cts
are
wire
d in
pa
ralle
l fo
r re
liab
ility
. T
he
se
are
ra
ted
at 1
0-1
5 A
mp
s D
C
3. F
or
co
rre
ct o
pe
ratio
n O
NL
Y o
ne
sw
itch
is o
pe
rate
d to
th
e "
ON
" p
ositio
n a
t a
ny o
ne
tim
e.
4. C
ase
fo
r th
e s
witch
es c
an
be
pla
stic o
r m
eta
l.
5. A
te
rmin
al is
pro
vid
ed
to
co
nn
ect th
e +
ve
of th
e p
ow
er
su
pp
ly to
th
e S
witch
-Bo
x. T
he
-ve
of th
e
po
we
r su
pp
ly c
on
ne
cts
to
th
e c
oa
x b
raid
co
nn
ectin
g th
e a
nte
nn
a. T
his
is to
pre
ve
nt a
n e
art
h lo
op
be
ing
cre
ate
d .
-
Po
we
r S
up
ply
12
v /1
3.8
v +
To
An
ten
na
Co
ax B
raid
EA5AVL COMPACT 4-SQUARE ANTENNA NOTES
1. Antenna wires are plastic coated single core, and shorter than normal due to Inter-capacitive effects between the other elements of the antenna etc. Also plastic coated wire will further reduce the calculated lengths slightly. The 40 metre version described here uses 665 feet or approximately 202 metres of insulated wire. The Ground wires are also single core plastic coated wire. 2. The antenna tuning will alter by 100 KHz for a change of 6 inches (15cm) in length Add more wire to LOWER the antenna frequency Remove some wire to INCREASE the frequency
REMEMBER it is easier to remove that add wire to an antenna.
Match the 50 Ohm coaxial cable power rating & insulator size to the power levels Of the transmitter to be used, i.e. RG-8X for power levels up to 400watts and RG213 over 400watts. 3. All guy ropes should be made of nylon or polypropylene so that the antenna tuning is not affected. The Tension for supporting the mast is in the guys not the antenna wires 5. The spreader Cross arms at the top of the mast are made from aluminium alloy
tubing & wooden broom handles, and designed to rotate horizontally. 6. The cross arms at the top of the antenna swivel so that any compass direction can be set to suit personal DX requirements 7. The mast is 36ft tall (11m) and should be made of a non-electrically conducting
material such as wood, but if a metal Mast is used, then it should be insulated from ground and be a non-resonant length.
8. The antenna feed point plates (antenna wire length adjusters) are made from 0.25 inch (6mm) thick Perspex sheet, but other plastics can be used. Black plastic is not recommended as this is loaded with carbon particles and will eventually break down and conduct. 9 The Reflector Tuning capacitor is a large air spaced version, 250 pF+250 pF wired
in parallel Measured as 10. The copper earth rods are 1.5 metres long and should be sited close to the antenna base and the Relay Box and the plastic Capacitor Box
TUNING THE EA5AVL COMPACT 4-SQUARE ANTENNA
1. The four wire vertical elements must be tuned to within a few hertz of each using an MFJ antenna analyser or by ensuring the SWR is the same for each wire. 2. The top cross arms are 16 feet long ( 4.9m) or 1/8 wavelength and the bottom spacing is 34 feet (10.4m) or (1/4 wavelength) 3. The variable 500 pF capacitor tunes the reflectors . The tuning is quite sharp and noticeable when listening to the transceivers via headphones extended to the antenna base by the antenna. This is very important if best performance of the antenna is to be achieved. 4. Four identical lengths of 1/4 wavelength 50 Ohm coaxes from the Relay Box to the Perspex plate feed points.
METHOD OF TUNING
5. Having erected the 4-wire antenna, tune each vertical element to the required frequency i.e. 7.050 kHz for the UK where as 7.100 KHz for the USA, by using the wing nuts at the bottom to shorten each wire make the adjustments. 6. An antenna analyser or SWR meter has to be used. The 500pF capacitor should be set to 3/4 meshed before adjusting any wire lengths. ( approx 350-400pf)
Do not alter until later !
TUNING THE ANTENNA - REFLECTORS
7. An MFJ-259B (or any similar RF Signal Device) with a short vertical antenna to radiate a low power RF signal is placed at least 100 feet ( 33m) away from the antenna. 8. Use a long cable to extend a pair of headphones from the transceiver to the capacitor box at the antenna mast base. 9. At the shack set the receiver to the signal frequency and select CW with a fast AGC setting. 10. Using the 4 -way Control Switch Box, to select the antenna element which is farthest away from the MFJ signal source, and adjust the receiver for an S7 signal. If the reading is steady, connect a long extension cable with some earphones and listen to the signal next to the capacitor box. 11. Ignore any static of other stray signals or noises. Use the 500pF capacitor to tune for a NULL signal in the earphones. This will be quite noticeable, and the receiver should then be showing a smaller reading, S1 or S2.
12. Tuning the variable capacitor for one compass direction will automatically tune the other directions.
ALTERNATE METHOD OF TUNING THE ANTENNA
13 Listen to ARRL CW practice transmission, weekdays, W1AW, USA transmissions on 7045.50 KHz between 2300-0100Z. Use the same procedure as in “5-12” above; again using the capacitor for a NULL. 14. There is also an Canadian SSB Net , transmissions on 7.063 KHz daily between 2300-2400Z The Net is called “The Sand Box Net” – listen out for the net controller and only use his signal – ignore any other signals. 15. Performing the reflector tuning during darkness is probably best i.e. During “DX time” when there is less local noise and the occasional nut case!
N.B. The EA5AVL Compact 4 –Square antenna is intended for DX working and is not suited for short haul communications i.e. around UK. With patience and attention to detail you will be pleased with the results.
EA5AVL RSARS 506
Copyright Notice 2007 There is no objection to this design being copied for non–commercial use and being passed to other individual Radio Amateurs or for Amateur Radio Clubs to use this design, as long as the origin of design is acknowledged.
ANSWERS TO FREQUENTLY ASKED QUESTIONS:- (Updated May 2008) A1. My name is Les EA5AVL/G3WMZ, ( RSARS Member 506) I have been a "ham" for 46 years, and served with the British Army Royal Corps of Signals Radio for 22 years, then 12 years with PHILIPS TELECOM as a Telecoms, radio and data engineer. I moved out to Spain 16 years ago, got married to a lovely lady and love it and off course the radio. I am now at the tender age of 74. A2. The 4 Square. I put it up 3 years ago and it is used on 40 meters almost every night for 4 hrs plus, all component parts are the same as they were when first erected no problem with relays, switches, etc., it has withstood gale force winds of the last 3 winters with no damage, the wire elements have stretched a little and now need slight attention. A3. My central support is 36ft tall and is insulated at the base on a "CHAMPAGNE" bottle. The aluminium mast and spreaders only act as a supporting structure. A4. The coax feed points on each element are 5 - 6ft above ground, the slopping wires are adjusted on the top wing nut off the plastic connection plate, to resonance. A5. Measuring the 500Pf variable tuning capacitor on the MFJ 259B measured 380Pf for capacitor 3/4 meshed when tuned. A6. RG213U coax is used throughout the system. A7. The 4 slopping wire elements were not measured, but are shorter than the expected 33ft 2ins due to : (a) plastic coating (b) capacity hats (c) mutual coupling. A8. Recent VSWR plot ( March 2008) shows that the wires have stretched a little over the 3 years, even so, the frequency of the 4 wires was within 8.0 KHz of each other. Resonant frequency = 6.930 SWR measured as 1 to 1 Bandwidth from resonant frequency = 1.18 MHz @ SWR 2 to 1 Points , 994Khz @ SWR 1.6 to 1, 600Khz @ SWR 1.3 to 1
On the MFJ gave the following readings appeared at: 6.930 SWR = 1.1 R44 - X 2 - coax loss 9db These measurements were taken on the shack end of the feeder 50hom coax cable, so one can see it is not a narrow HI Q system, however 30db plus front to back is obtained from at least 7megs to 7.150megs, my oper-ating range. A9. EA5AVL Stations is located 25 miles west of Alicante & operates on CW & SSB modes using ICOM PRO3 + Kenwood TL922AMP at 500 Watts A10 Stations worked SSB last 2 wks March-April 2008 … during Low Sunspot activity March 15 PY4 - PY2 - TI2 - 6W1, March 17 VA3 - VE3 - NA4 “ 19 UN7 “ 20 W4 - AA4 - KB8 - 5T5 - VQ9 “ 25 ZS1 - VK7 - JA5 - VR10 - VK6 - YB0 " 26 V01 - FG - VE1 “ 27 D44 - VE3 - HK1 “ 28 NC1 - NQ4 - VA2 - KP2 - 8P9 " 29 K3 - NE1 - KY1 - KD4 “ 31 9K2 April 1 C08 - VK7 April 3 7X5 “ 6 VP2 - PY1 7 W1 - N5 - K4 - K3. Lowest report 5 and 7 Highest report 5 and 9 + 20, Farthest north = Iceland and Japan over North Pole , Farthest east = YB0 VK6 VK7, Farthest south = Antarctica ZS1, Farthest west = XE1 CE.
Best wishes from 25 miles west of Alicante Spain Les EA5AVL/G3WMZ and Alexia (the computer slave)