Hy-Gain AV-18HT, Instruction Manual, Page: 33 / 36

The 1/4 and 1/2 wave transformers, identified as L3, L4 and L5 are calculated from the
lowing formula:
1/4 wave
246000 x vel.
f
vel. factor - reg. coax.
0.66
frequency (in KHz)
EXAMPLE:
1/4 wave at 7200 KHz = 246000 / 7200 = 34.16
34.16
x.75
25.62
1/4 wave = 25.62
ft.
P A R T 2 - M U L T I - B A N D O P E R A T I O N
M U L T I - B A N D I N G
RADIATION PATTERN:
Multi-banding is easily accomplished by
choice spacing two identical verticals. (refer
to charts A,B, and C and associated Figures 1
through 5) Switchable 1/4 wave length and 1/2
wave length phasing cables must be employed
for each band. These cables can be placed in
the station in any suitable fashion along with a
manual switching arrangement or relay
system. Consideration must be given to the fact that 1/2
wave spacing (optional) is ideal for phasing.
When multi-banding with close and wide spac-
ing, compromise radiation patterns must be
expected. In most cases a choice spacing serves
3 bands most effectively with good directional
characteristics, added gain and low angle per-
formance.
E L E C T R I C A L S P E C IFICATIONS:
VSWR: Exceptionally low SWR is present with a phased array. If phasing lines are
correctly measured and the terminal impedance of each antenna is very close to 50 Ohms:
Typical SWR: Broadside 1.2:1, Endfire 1.4:1, Cardioid 1.2:1.
P H A S I N G L I N E S :
Two Phased Verticals Three Phased Verticals
Pattern Width, half power points 120 degrees 60 degrees
Gain over single vertical 4.5 dB 4.5 dB
Side attenuation 20 dB 20 dB
Rear attenuation 30 dB 30 dB
Impedance 50 Ohms 50 Ohms
Directional Characteristics Uni-directional Uni-directional