RadioShack HTA-20 Owner Manual

RADIO SHACK LIMITED WARRANTY

This product is warranted against defects for 1 year from date of pruchase
from Rad.io Shack company-owned stores and authorized Radio Shack
franchisees and dealers. Within this period, we will repair it without charge for
parts and labor. Simply bring your Radio Shack sales slip as proof of
purchase date to any Radio Shack store. Warranty does not cover
transportation costs. Nor does it cover a product subjected to misuse or
accidental damage.

EXCEPT AS PROVIDED HEREIN, RADIO SHACK MAKES NO

WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WARRANTIES OF

MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
Some states do not permit limitation or exclusion of implied warranties;

therefore, the aforesaid Iimitation(s) or exclusion(s) may not apply to the

purchaser.

This warranty gives you specific legal rights and you may also havo othar rights which
vary from state to state.

We Service What We Sell

Cat. No. 19-1122

OWNER'S MANUAL

j

l

8M

RADIO SHACK

A Division of Tandy Corporation

Fort Worth, Texas 76102

Printed in Korea

!

!ladle Ihaek®

-----------_\._~~~~

FEATURES

Your Radio Shack HTA-20 VHF Amplifier with RX Pre-
Amplifier is a high-power, filtered VHF band amplifier

designed for use with transceivers in the 144 - 148 MHz
FM frequency band. When your transceiver transmits, the
amplifier amplifies the transmitted power.

Its features include:

Bipolar Transistor High Power Amplifier - increases a
normal transceiver's output power from 0.5 - 5 Watts up to
30 Watts.

Double Tuned Helical Band Pass Filter - reduces out-

of-band interference by allowing the received frequencies

in the 144 - 148 MHz band to easily enter the receiver but
attenuating all other frequencies.

Low Noise GaAs Field Effect Transistor (FET) Pre-
Amplifier - normalizes insertion loss and provides clean

received signal gain.

Note: This amplifier is designed to be used only with a

high-power antenna.

CONTENTS

Preparation 4

Mounting the Amplifier 4
Installing an Antenna 6
Making the Connections 7
Matching the Antenna's Standing

Wave Radio (SWR) 11
Operation 13
Troubleshooting 14

Maintenance 16

Caring for Your HTA-20 16

Replacing the Fuse 17

Specifications 18

© 1994 Tandy Corporation.

All Rights Reserved.

Radio Shack is a registered trademark used by Tandy Corporation.

2

3

PREPARATION

- \

The most common place to mount an amplifier is under a
vehicle's dashboard. Choose a specific location where:

• You can easily reach the amplifier.

• The amplifier's wires and RF cables reach their con-
nection points and do not interfere with any of the vehi-
cle's moving parts.

• The amplifier is not directly in front of air vents.

MOUNTING THE AMPLIFIER

Warning: Mount the amplifier securely to avoid damage

to the amplifier or vehicle and to prevent injury to anyone
in the vehicle during sudden starts or stops.

Follow these steps to mount the amplifier.

1. Mark the positions for the screw holes using the supplied
mounting bracket as a template.

2. Drill the screw holes into the mounting surface at each
marked locations.

Caution: Be sure you do not drill into electrical wires
behind the mounting surface or into any of your
vehicle's moving parts.

4

3. Attach the mounting bracket to the mounting surface
using a Phillips screwdriver and the supplied mounting

screws and washers.

4. Attach the amplifier to the mounting bracket with the
supplied mounting knobs.

Note: The mounting knobs are large and slotted so
you can easily tighten them with either your fingers or
a large flat-blade screwdriver. Do not over-tighten.

5

INSTALLING AN ANTENNA

Caution: Do not run the cable:

Be sure to use the amplifier only with a high power
antenna. Consult your local Radio Shack store for as-
sistance in selecting an appropriate antenna.

Caution: Due to the amplifier's high power output, a low

power antenna will get hot within a few minutes after

starting transmissions. An over-heated antenna causes

SWR (Standing Wave Radio) degradation which can

damage the RF power transistor, and in some cases,

damage or destroy the antenna.

• When selecting the antenna's mounting location:

• Mount the antenna vertically and as high as possible on
a vehicle.

• Mount the antenna and route the RF cable as far as

possible away from electrical noise sources (ignition

system, gauges, etc.).

Follow the mounting instructions supplied with the
antenna, then route the antenna's RF cable to the am-
plifier.

• Over sharp edges or moving parts that might damage
the cable.

• Next to power cables or other communication unit's
antenna cables.

• Through the engine compartment or other areas that
produce extreme heat.

MAKING THE CONNECTIONS

Cautions:

• When used in a vehicle, the amplifier is designed to
work with a 12-volt, negative ground electrical system.
If you are unsure about your vehicle's electrical system
type, check with your vehicle's dealer.

• To avoid damage to the amplifier's RF power transistor
when you use a DC power supply instead of a vehicle's

12-voltelectricalsystem, useonly a powersupply(such as

Cat. No. 22-120)that is fully protectedagainst over-voltage

and high frequency intrusion and is capable of supplying
high current.

6

7

• To prevent damage to your amplifier, do not apply power
to it until after you connect an antenna.

Notes: To achieve full rated power output when using:

• Your vehicle's electrical system, your vehicle should be
running so the nominal input power to the amplifier is

13.8V DC.

• A DC power supply, set the output to 13.8 volts.

3. Push and turn counterclockwise the fuse holder in the
amplifier's red wire, pull the holder apart, and remove

the fuse.

~~

1. Set POWER to the off position.

~ ~

POWER TX

POWER

off

2. Remove the power source by doing one of the following:

• Disconnect your car battery's negative terminal.

• Turn off the DC power supply.

8

4. Connect the amplifier's black wire to a metal part of
your car, such as your transceiver's ground source.

5. Connect the amplifier's red wire to a source of 12-volt
DC power, such as your transceiver's power source.

DC 13.8V ANT OUTPUT

@ r...i ~ ~ @

To Switched

12V DC

Black Wire to Ground

9

6. Connect your transceiver's antenna RF cable to the

TX INPUT connector on the back of the amplifier.

ANT OUTPUT TX INPUT

®

~ ~@

7. Connect the antenna to the ANT OUTPUT connector
on the back of the amplifier.

8. Place the fuse inside the fuse holder, then push the
holder's ends together and tighten them by turning

the holder clockwise.

1

9. Reapply the DC power source by doing one of the

l

following:

• Reconnect your car battery's negative terminal.

• Turn on the DC power supply.

10

Antenna

50 ohm RF Cable

I'-J

I ~ (g) [g) g]l
I [Q] [Q] [Q] QJI'[g] IQ] [Q lQl

I~===cil

.- -=

MATCHING THE ANTENNA'S
STANDING WAVE RATIO (SWR)

After making all the connections and before you begin
operating the HTA-20, test your transceiver and match

)

your antenna's SWR for top performance using an SWR
meter (not supplied).

1

11

OPERATION

Notes:

• Make sure the SWR meter can measure the 144-
148 MHz frequency band and an output power of at

least 30 Watts .

• Verify the SWR using the transceiver's low power
before turning on the amplifier to fine tune the SWR
at high power.

Use the instructions supplied with the SWR meter to
measure and adjust your antenna to the lowest SWR
value. Ideally, the SWR should be as low as 1.0:1. To
be acceptable, the SWR must be less than 1.3:1.

To turn on the transceiver, set POWER to ON.

Set POWER on the amplifier to on. The POWER indicator
lights.

,I,

- c:::I - c:::I

POWER TX

POWER

[DON

When your transceiver transmits, its low-power signal is
sent to the HT A-20. The amplifier boosts the transmitted
power and sends the signal to the antenna for transmis-

sion. The TX indicator lights during transmission.

When your transceiver receives, the received signals are
routed through the amplifier's helical narrow band pass filter
to reduce undesirable out-of-band signal interference,
amplified by the low-noise GaAs FET pre-amplifier, then sent

back to the transceiver.

12

13

TROUBLESHOOTING

If your amplifier is not working as it should, follow these

suggestions to see if you can eliminate the problem. If you

cannot eliminate the problem, take the amplifier to your IOi
cal Radio Shack store for assistance.

Check the red and black wires'

Symptom

and transceiver.

the amplifier and the antenna

vehicle battery or DC powersupply) and the in-line fuse

(replace only with an 8-amp fuse).

short/open.
Check all cables and wires for

Check the power source (either

connections.

Check all cables and insure they

are securely connected between

Check all cables for short/open

and be sure they are connected.

Suggestion

Output power is less

than the rated level.

Symptom

insure it is a 12 volt source.

rated level (0.5 to 5 Watts).
Check the power source to

from the transceiver is within the

Check that the driving power

Suggestion

14

15

MAINTENANCE

CARING FOR YOUR HTA-20

Your Radio Shack HTA-20 VHF Amplifier with RX Pre-
Amplifier is an example of superior design and craftsman-
ship. The following suggestions will help you care for your
amplifier so you can enjoy it for years.

Keep the amplifier dry. If it gets wet, wipe
it dry immediately. Liquids contain minerals

that can corrode electronic circuits.

Handle the amplifier gently and carefully.
Dropping it can damage circuit boards and

Cj

~~

(j

cases, and can cause it to work improperly.

Keep the amplifier away from dust and dirt,
which can cause premature wear of parts.

Wipe the amplifier with a damp cloth
occasionally to keep it looking new. Do not
use harsh chemicals, cleaning solvents, or
strong detergents to clean it.

Modifying or tampering with the amplifier's internal
components can cause a malfunction and void your
authorization to use it. If your amplifier is not performing
as it should, take it to your local Radio Shack store for

assistance.

REPLACING THE FUSE

1. Set POWER on the amplifier to off and turn off the power
source.

2. Hold the amplifier's in-line fuse holder by both ends,
push and turn it counterclockwise, then pull it apart.

3. Replace a blown fuse with an 8-amp fuse of the same
type and rating.

4. Push the holder's ends together and tighten them by

turning the holder clockwise.

16

17

SPECIFICATIONS

Frequency Band 144-148 MHz VHF Band
Frequency Mode F3 (FM)

RF Output Power 30 Watts
Input Power 0.5 - 5 Watts
Power Source DC 13.8V

Negative Ground Max Current 6 Amp Max
Spurious Level Less than - 60 dB

Net Gain (Receiver with Helical Filter) 0 dB
Receiver Bandpass Filter Double Tuned Helical
In/Out Impedance ,50 Ohm
In/Out Connector M Type
Dimensions (HWD) 1V2 x/3% x 6% Inches

Weight 1
Specifications are typical: Individual units may vary.

Specifications are subject to change and improvement

without notice.

3,4 Ibs

NOTES

18

19