21-533.fm Page 1 Thursday, August 5, 1999 3:47 PM
Cat. No. 21-533
OWNER’S MANUAL
Please read before using this equipment.
CB/Ham Field-Strength
SWR Meter
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 3 Thursday, August 5, 1999 3:47 PM
CONTENTS
Measuring SWR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Connecting the Meter . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Calibrating the Meter/Measuring SWR . . . . . . . . . . . . . 5
Interpreting SWR Readings . . . . . . . . . . . . . . . . . . . 8
Improving SWR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Measuring Field Strength . . . . . . . . . . . . . . . . . . . . . . . . 10
Preparing the Antenna Site . . . . . . . . . . . . . . . . . . . . 11
Calibrating the Meter/Measuring Field Strength . . . . . 13
Using Field Strength Readings to Tune Your Radio
and Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Care and Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Schematic Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 4 Thursday, August 5, 1999 3:47 PM
MEASURING SWR
Measuring SWR shows you how much of your radio’s transmit
power is reflected from the antenna back into the antenna ca-
ble, generating heat and wasting power. With this information,
you can adjust the length of your antenna or antenna cable so
your antenna and radio combination can produce the maxi-
mum power they are capable of producing.
For more information about measuring SWR, see the ARRL
Handbook, available at your local library.
CONNECTING THE METER
To connect this meter to your CB or amateur radio and your
antenna, you need RG-58U coaxial cable (not supplied) with
a PL-259 connector on both ends (such as RadioShack Cat.
No. 278-968). The cable must reach from the back of the
meter to your radio’s antenna jack.
Follow these steps to connect the meter to your radio and an-
tenna.
4
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 5 Thursday, August 5, 1999 3:47 PM
1. Turn off your radio. Then disconnect the antenna from
the radio and plug it into ANTENNA on the back of the
meter.
2. Plug the coaxial cable into the radio’s antenna jack and
into TRANSMITTER on the back of the meter.
CALIBRATING THE METER/
MEASURING SWR
1. Set CALIBRATION/FS/SWR on the front of the meter to
CALIBRATION/FS.
2. Turn on your radio. Then select a channel or frequency
on your transmitter and hold down its transmit key. Do not
speak into the microphone.
Notes:
•
An SWR reading will be different for different frequen-
cies (channels). If you transmit on one channel more
often than any other, select that channel. If you trans-
5
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 6 Thursday, August 5, 1999 3:47 PM
mit on several channels, choose a frequency in the
middle of the range of channels you use. (For example,
if you transmit on all 40 CB channels, choose Channel
20, because it is midway between Channel 1 and
Channel 40.)
•
•
If you use a CB that has sideband modes (SSB), do not
select any of these modes. (Use only AM for SWR
measurements).
If you have an amateur radio, select the continuous
wave (CW) or tuning mode to check the SWR.
3. While you hold down the transmit key, rotate the meter’s
knob until the needle points to CAL.
4. Release the transmit key, then set CALIBRATION/FS/SWR
to SWR.
6
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 7 Thursday, August 5, 1999 3:47 PM
5. Press the transmit key again, then read the SWR by not-
ing the needle’s position on the upper SWR scale. A
meter reading of 1 on the upper scale is ideal.
SWR Scales
The figure shown between the upper and lower scales on
the meter (% REF POWER) indicates the percentage of
power that is wasted through reflection of the signal from
the antenna back into the antenna cable. For example,
an SWR reading of 1.5 also means that 4% of your signal
power is lost. However, 96% of the radio power is more
than enough for almost all applications.
6. Repeat Steps 1–5 for each channel or frequency you
want to get an SWR reading for.
7
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 8 Thursday, August 5, 1999 3:47 PM
Interpreting SWR Readings
An ideal SWR reading is 1.0, but this reading is usually possi-
ble only under laboratory conditions or with a dummy load. Ac-
tual antenna installations have higher readings. The in-
formation below will help you interpret the readings you get.
SWR
Efficiency
Interpretation
1.0 to 1.5
Excellent
The antenna cable and the
antenna length match the
transmitter’s output require-
ments almost perfectly.
1.5 to 2.0
2.0 to 3.0
Very good
The antenna, the cable, and
the transmitter operate very
efficiently.
Acceptable The antenna, the cable, and
the transmitter operate with
some loss. If possible, adjust
your antenna or antenna
mounting system to improve.
Above 3.0
Inefficient
Adjust your antenna or
antenna mounting system to
improve efficiency.
8
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 9 Thursday, August 5, 1999 3:47 PM
IMPROVING SWR
There are several ways to improve the SWR of your radio/an-
tenna combination. Try these first.
• Be sure you are using the type of cable recommended for
your equipment. If the manufacturer recommends a 50-
ohm cable, do not substitute another type that has a dif-
ferent impedance.
• Confirm that you mounted your antenna according to the
manufacturer’s instructions. The angle and the base
arrangement can affect the SWR reading.
• Adjust the length of your antenna according to the
instructions provided by the manufacturer. A change of
1
as little as /8 inch can make a measurable difference.
• See your radio’s and antenna’s owner’s manuals.
9
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 10 Thursday, August 5, 1999 3:47 PM
MEASURING FIELD STRENGTH
Your meter can measure the low levels of radio frequency (RF)
generated by a radio transmitter. You can use these measure-
ments to map the transmitting direction and coverage pattern
of your antenna, or to compare your radio and antenna’s effi-
ciency before and after an adjustment. You do not need to con-
nect the meter to the antenna or the radio to measure field
strength.
It takes two people to measure field strength. For an accurate
measurement, you will need to map the site around your anten-
na. Then, while someone presses the radio’s transmit key, you
will need to walk around the site around your antenna with the
meter, marking the readings you see.
Hints:
• In addition to the meter, we recommend you use the fol-
lowing items to help you measure field strength:
— Several photocopies of the template on Page 11
— 36 objects such as rocks or weighted pieces of paper
— 25 feet of rope or strong cord
— Calculator
— Pencil
— Compass
• Make sure there is at least 25 feet of open space in all
directions around your antenna.
10
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 11 Thursday, August 5, 1999 3:47 PM
PREPARING THE ANTENNA SITE
Before you use the meter to measure field strength, you should
mark the site around the antenna in a pattern that will help you
make the measurement.
An easy way to do this is to map the area around your antenna
using a template like this one.
Antenna Location
11
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 12 Thursday, August 5, 1999 3:47 PM
The template shows an imaginary circle around an antenna.
The spokes on the template represent imaginary straight lines
measured from the center of the circle to 36 points spaced
equally around the circle. Each straight line is 25 feet in length.
The numbers on the template (1–5) are a guide to show you
where to mark the field strength level the meter displays as you
measure.
Hint: To help measure a circular path around the antenna, tie
a slip knot in a 25-foot piece of rope or strong cord, slide the
knot loosely around your antenna, then use the rope as a guide
as you walk around the antenna.
Follow these steps to prepare the antenna site.
1. Starting at the antenna, use a compass to find due north.
Then walk due north and stop about 15 to 25 feet away
from the antenna.
2. Use an object such as a rock or a weighted piece of paper
to mark where you are standing.
3. Walk around the antenna in a circle, using more objects to
mark 35 more evenly spaced marks on the path.
Hint: You can quickly find the space to leave between each
mark by using a calculator. Measure the diameter of the
marked circle (from one side of the circle to the other). Then,
divide the diameter by 11.46.
12
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 13 Thursday, August 5, 1999 3:47 PM
For example, for a 50-foot diameter circle:
50 feet
= 4.363 Feet
11.46
So, you would place a mark every 4.363 feet (4 feet, 3 inches).
CALIBRATING THE METER/
MEASURING FIELD STRENGTH
Important:
Be sure to follow any radio service regulations that
limit the amount of time you can transmit without a break or sta-
tion identification.
1. Remove the supplied short wire antenna attached to the
bottom of the meter, then insert it into FS ANT on top of the
meter.
13
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 14 Thursday, August 5, 1999 3:47 PM
2. Set CALIBRATION/FS/SWR to CALIBRATION/FS.
3. To calibrate the meter, have your helper select a channel
or frequency on your transmitter and hold down its trans-
mit key. Tell the helper not to speak into the microphone.
Then, while the helper holds down the transmit key, walk
around inside the marks you made using the steps in
“Preparing the Antenna Site” on Page 11, covering as
much area inside the circle as you can. As you walk,
watch the meter’s needle. If it moves to the right of 5 on
the FIELD STRENGTH scale, rotate the knob on the front
of the meter until the needle lines up with 5 on the scale.
Notes:
•
If you use a CB that has sideband modes (SSB), do not
select any of these modes. (Use only AM for field
strength measurements).
14
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 15 Thursday, August 5, 1999 3:47 PM
•
If you have an amateur radio, select the continuous
wave (CW) or tuning mode to check the field strength.
4. To measure field strength, as the helper continues to hold
down the transmit key, move to the marked spot on the
circle due north of the antenna, then watch the meter’s
needle.
Note the reading on the FIELD STRENGTH scale and
place a dot on the template on Page 11 corresponding to
the reading at that point.
In this example, the needle shows a 4 on the FIELD
STRENGTH scale. Place a dot where the spoke repre-
sentating the path you walked from the center of the circle
intersects the circle marked with a 4 on the template.
Direction of Travel
Dot
You are Here
15
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 16 Thursday, August 5, 1999 3:47 PM
5. Move to each marked spot along the circular path then
repeat Step 4 for each one, taking another reading and
recording that reading on the template.
Here is an example of a completed template. It shows an an-
tenna mounted on the rear bumper of an automobile that is
parked facing north. The field strength readings form a two-
lobed pattern when plotted, meaning the antenna’s power is
greatest at the front, weaker at the back, and almost nonexist-
ent at the sides.
16
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 17 Thursday, August 5, 1999 3:47 PM
USING FIELD STRENGTH READINGS
TO TUNE YOUR RADIO AND ANTENNA
You can use field strength measurements to monitor the effec-
tiveness of changes you make to your radio and antenna while
you make them. Changes you might make include:
• Installing a new antenna or antenna cable
• Adjusting the length of an antenna
• Changing the antenna mount on your vehicle
• Adjusting your radio’s transmitter
You do not need to connect the meter to the antenna or the ra-
dio to measure field strength, but you will need two people.
While someone presses the radio’s transmit key, you will need
to note the readings you see on the meter.
Important:
Be sure to follow any radio service regulations that
limit the amount of time you can transmit without a break or sta-
tion identification.
1. Remove the supplied short wire antenna attached to the
bottom of the meter, then insert it into FS ANT on top of the
meter.
2. Set CALIBRATION/FS/SWR to CALIBRATION/FS.
3. To calibrate the meter, have your helper select a channel
or frequency on your transmitter and hold down its trans-
mit key. Tell the helper not to speak into the microphone.
17
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 18 Thursday, August 5, 1999 3:47 PM
Then, while the helper holds down the transmit key, walk
around and adjust the meter’s knob until the meter’s nee-
dle moves to 3 on the FIELD STRENGTH scale.
Notes:
•
•
If you use a CB that has sideband modes (SSB), do not
select any of these modes. (Use only AM for field
strength measurements).
If you have an amateur radio, select the continuous
wave (CW) or tuning mode to check the field strength.
4. Have the helper release the transmit key, then make a
change to your radio or antenna (such as adjusting the
antenna or transmitter or adding a new antenna).
5. When the change is completed, have the helper hold
down the transmit key again while you watch the meter’s
needle.
If the field strength reading is higher, you have probably
improved the power output and efficiency of your radio
and antenna. If the field strength reading is lower, repeat
Steps 4 and 5.
Note: If you move the physical location, or change the
transmission direction, of your antenna, you might have to
recalibrate the meter and measure the field strength
again. See “Calibrating the Meter/Measuring Field
Strength” on Page 13.
18
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 19 Thursday, August 5, 1999 3:47 PM
CARE AND MAINTENANCE
Your RadioShack CB/Ham Field-Strength SWR Meter is an
example of superior design and craftsmanship. The following
suggestions will help you care for your meter so you can en-
joy it for years.
Keep the meter dry. If it gets wet, wipe it dry im-
mediately. Liquids can contain minerals that can
corrode the electronic circuits.
Handle the meter gently and carefully. Dropping
it can damage circuit boards and cases and can
cause the meter to work improperly.
Use and store the meter only in normal temper-
ature environments. Temperature extremes can
shorten the life of electronic devices and distort
or melt plastic parts.
Keep the meter away from dust and dirt, which
can cause premature wear of parts.
Wipe the meter with a damp cloth occasionally
to keep it looking new. Do not use harsh chem-
icals, cleaning solvents, or strong detergents to
clean the meter.
19
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 20 Thursday, August 5, 1999 3:47 PM
Modifying or tampering with your meter’s internal compo-
nents can cause a malfunction and might invalidate the
meter’s warranty and void your FCC authorization to operate
it. If your meter is not operating as it should, take it to your lo-
cal RadioShack store for assistance.
20
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 21 Thursday, August 5, 1999 3:47 PM
SCHEMATIC DIAGRAM
(illus - show schematic diagram
of meter)
21
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 22 Thursday, August 5, 1999 3:47 PM
SPECIFICATIONS
Measurable RF Power ..................................... 1–1000 Watts
SWR ................................................................................ 1–3
Impedance .............................................................. 50 Ohms
Frequency Range ................................................. 3–30 MHz
Dimensions (HWD) ...................... 29/16 ¥ 65/16 × 315/16 Inches
(65 ¥ 160 ¥ 100 mm)
Weight ............................................................................ 8 oz
(226 g)
Specifications are typical; individual units might vary. Specifi-
cations are subject to change and improvement without no-
tice.
22
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 23 Thursday, August 5, 1999 3:47 PM
Limited Ninety-Day Warranty
This product is warranted by RadioShack against manufacturing defects in ma-
terial and workmanship under normal use for ninety (90) days from the date of
purchase from RadioShack company-owned stores and authorized Ra-
dioShack franchisees and dealers. EXCEPT AS PROVIDED HEREIN, Ra-
dioShack MAKES NO EXPRESS WARRANTIES AND ANY IMPLIED
WARRANTIES, INCLUDING THOSE OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE, ARE LIMITED IN DURATION TO THE DU-
RATION OF THE WRITTEN LIMITED WARRANTIES CONTAINED HEREIN.
EXCEPT AS PROVIDED HEREIN, RadioShack SHALL HAVE NO LIABILITY
OR RESPONSIBILITY TO CUSTOMER OR ANY OTHER PERSON OR EN-
TITY WITH RESPECT TO ANY LIABILITY, LOSS OR DAMAGE CAUSED DI-
RECTLY OR INDIRECTLY BY USE OR PERFORMANCE OF THE PRODUCT
OR ARISING OUT OF ANY BREACH OF THIS WARRANTY, INCLUDING,
BUT NOT LIMITED TO, ANY DAMAGES RESULTING FROM INCONVE-
NIENCE, LOSS OF TIME, DATA, PROPERTY, REVENUE, OR PROFIT OR
ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES,
EVEN IF RadioShack HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
DAMAGES.
Some states do not allow the limitations on how long an implied warranty lasts
or the exclusion of incidental or consequential damages, so the above limita-
tions or exclusions may not apply to you.
In the event of a product defect during the warranty period, take the product and
the RadioShack sales receipt as proof of purchase date to any RadioShack
store. RadioShack will, at its option, unless otherwise provided by law:
(a) correct the defect by product repair without charge for parts and labor; (b) re-
place the product with one of the same or similar design; or (c) refund the pur-
chase price. All replaced parts and products, and products on which a refund is
made, become the property of RadioShack. New or reconditioned parts and
products may be used in the performance of warranty service. Repaired or re-
placed parts and products are warranted for the remainder of the original war-
ranty period. You will be charged for repair or replacement of the product made
after the expiration of the warranty period.
(continued)
23
Download from Www.Somanuals.com. All Manuals Search And Download.
21-533.fm Page 24 Thursday, August 5, 1999 3:47 PM
(continued) This warranty does not cover: (a) damage or failure caused by or at-
tributable to acts of God, abuse, accident, misuse, improper or abnormal usage,
failure to follow instructions, improper installation or maintenance, alteration,
lightning or other incidence of excess voltage or current; (b) any repairs other
than those provided by a RadioShack Authorized Service Facility; (c) consum-
ables such as fuses or batteries; (d) cosmetic damage; (e) transportation, ship-
ping or insurance costs; or (f) costs of product removal, installation, set-up
service adjustment or reinstallation.
This warranty gives you specific legal rights, and you may also have other rights
which vary from state to state.
RadioShack Customer Relations, Dept. W, 100 Throckmorton St., Suite 600,
Fort Worth, TX 76102
We Service What We Sell
3/97
RadioShack
A Division of Tandy Corporation
Fort Worth, Texas 76102
811081260A
3A8
Printed in China
Download from Www.Somanuals.com. All Manuals Search And Download.
|