Hy-Gain 18AVT instruction manual

INSTRUCTION

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per,

MANUAL

Installation of this product near power lines is
dangerous.
directions.

your safety, follow the installation

For

ORDER NO. 386S

Model 18 AVT/WB-S Vertical
Radiator, Amateur Antenna

WARNING

General
Descri

Theory of
Operation

tion

The Hy-Gain 18AVT/WB-S is an omnidirectional, self-supporting, vertical
radiator that operates in the 10, 15, 20, 40, and 80 meter amateur bands. The
system will work against earth ground or a resonant radial system when
mounted above ground. You make your own radial system following the
manual, or

Performance of the antenna can be optimized for either phone or CW with
either a ground or roof mount. Regardless of the optimization, the VSWR
bandwidths of the antenna are broad enough for the antenna to operate at a
VSWR of 2:1 or less from 10 to 40 meters. The bandwidth for 80 meters is
shar

The 18AVT/WB-S now features stainless steel hardware for all electrical and

Heavy-duty "Hy-Q Traps" give automatic band selection. The Hy-Q traps are
parallel resonant circuits which isolate the various sections of the antenna.
This provides true

ou can use t he Hy-Gain 14RMO radial system kit.

because the antenna is top loaded.

1

/4-wavelength resonance on all bands. The top hat and

Specifications

Electrical

Frequency . ........……....... 80, 40, 20, 15, and 10 meter amateur bands

Input Impedance ..............………………………..............................50 ohms

SWR at Resonance .......……………………............................... less than 2:1

Power Capabilities.............…………………................................ 2 kW PEP'

Lightning Protection ...........…………………............................... DC ground

Input Connector .............. . . . . . . . . . . . . . . . . . . . . . . . : . . . . . . . . . . SO-239

Mechanical

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Overall Height ..... ..........................………………......... 25' (7.62 m) nominal

Mast ..... : ................... ..... ...……………........ . accepts up to 1 5/8" (4.1 cm)

Wind Survival .......……………………............................... 80 mph (129 k mph)

Choosing a Site

'Maximum

ower on 80 meters is 1 kW PEP

NOTE: If the terminals of the input connector are checked with an ohmmeter,
they will show a direct short. This is normal! The matching coil in the antenna
base puts the entire system at DC ground, but presents a perfect 50 ohm
im

edance to RF energy.

A good ground is imperative for any vertical antenna system.

The 18AVT/WB-S can be mounted on the ground, on a rooftop or on a mast.
When mounting the antenna above ground, remember that you must also
install a ground plane radial system. When the antenna-is ground-mounted, a
radial system is usually not needed. But in some areas, where soil surface
conductivity is poor and a good ground cannot be made using the method
shown in Figure 4, you will need to lay out ground radials to improve the
efficiency of your antenna.

If you mount your antenna on a roof and find the roof space is too small for a
radial system, you can droop the radials over the edge of the roof at almost
any angle without seriously changing the performance of the antenna. The
radial system must be insulated from the roof and connected to a good

round for lightning protection.

Assembly
and
Installation

Read through the manual before beginning assembly. Also, acquaint yourself
with the illustrations by checking the parts as you take them from the carton.

Decide where you will mount your antenna (rooftop or ground) and what mode
of transmission you will use (phone or CW). Take special notice of the
dimensions in Figure 1. The antenna parts must be set to the exact
dimensions given, or it will not operate at peak efficiency. The VSWR charts

WARNING

Isolate the antenna from the reach of children or pets. The antenna
radials are hot with RF proportional to the operating power.

CAUTION

The antenna dimensions must be set either for CW operation on all bands
or phone operation on all bands. It is not possible to mix phone and CW
dimensions to allow operation of some bands on CW and some bands on
phone.

NOTE: The compression clamps used with this antenna are-used in many

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varied applications, so the screw head may or may not contact the
lockwasher or clamp body. Once it is tight, do not force the screw by
tightening it further. To do so may damage both the clamp and tubes. Do not
tighten any of the compression clamps until instructed to do so.

M1

Section
Assembly

M2
Section

M3

Section

Refer t o Figure 1 to ass em b le t h e m ain po rt i o n of th e
antenna.

Install a

1 1/4"

compression clamp (Item No. 16), untightened, over the M1
section (Item No. 9) (the base is attached to it already). Slip the M2 section, 1
1/8" x 26", (Item No. 4) into th e top of the M1 an d set t he M2 at d imens ion "A ",
as shown. Slip the clamp into place around the top of the M1 and tighten it

ust enough to keep the M2 from slipping.

Install an untightened 1 1/8” compression clamp (Item No. 17) over the M2.
Then slip the 10-meter trap (Item No. 10) bottom-first into the M2 butting it
against the top of the M2. (The top of this trap has a plastic cap on it.)

Slide the clamp into place around the top of the M2 and tighten it just enough
to kee

There are two M3 sections supplied-one for ground mounting, 1 1/8" x

the trap from slipping.

5 7/8"

(Item No. 2) and one for roof mount, 1 1/8" x 9", (item No. 5). Choose the
correct one for your installation and slide it onto the end of the 10-meter trap.
Place a 1 1/8" compression clamp (Item No. 17) around the lower end of the
M3. Then set the M3 at dimension "B" and tighten the clamp just enough to
keep the M3 from slipping.

M4

Section

Assembly

NOTE: There is a drainage hole in the side of the tube above the trap. Align
this hole with the slot in the M3 to allow

er drainage.

Install a second, untightened 1 1/8" compression clamp over the M3. Slip the
15meter trap (Item No. 7) into the M3. Set it at dimension "D" and tighten the
clamp just enough to keep it from slipping.

There are two M4 sections supplied-one for ground mount, 1 1/8" x 14" (Ite m
No. 36), and one for roof mount, 1

y8"

x 12" (Item 37). Choose the correct one
for your installation and slide it onto the end of the 15-meter trap. Place a 1
1/8" compre ss i o n c lam p ar o u nd th e lo we r en d of th e M4. Set the M4 a t
dimension "E" and tighten the clamp just enough to keep it from slipping.

NOTE: There is a drainage hole in the side of the tube above the trap. Align
this hole with the slot in the M4 to allow

er drainage.

Figure 1 Antenna Assembly