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Table of Contents
Related Manuals for Radio Shack 21-533
Summary of Contents for Radio Shack 21-533
- Page 1 Cat. No. 21-533 OWNER’S MANUAL Please read before using this equipment. CB/Ham Field-Strength SWR Meter...
- Page 2 INTRODUCTION Your RadioShack CB/Ham Field-Strength SWR Meter helps you tune your CB or amateur radio system for the best per- formance. CB and amateur radio systems work best when the antenna system’s impedance matches the transmitter’s output im- pedance as closely as possible. The meter’s standing wave ratio (SWR) function helps you trim your antenna to the pre- cise length you need for the maximum transmitted power.
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Page 3: Table Of Contents
CONTENTS Measuring SWR ....... . . 4 Connecting the Meter ......4 Calibrating the Meter/Measuring SWR . -
Page 4: Measuring Swr
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. -
Page 5: Calibrating The Meter/Measuring Swr
1. Turn off your radio. Then disconnect the antenna from the radio and plug it into on the back of the ANTENNA meter. 2. Plug the coaxial cable into the radio’s antenna jack and into on the back of the meter. TRANSMITTER CALIBRATING THE METER/ MEASURING SWR... - Page 6 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.) •...
- Page 7 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.
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Page 8: Interpreting Swr Readings
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. Efficiency Interpretation 1.0 to 1.5... -
Page 9: Improving Swr
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. -
Page 10: Measuring Field Strength
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. -
Page 11: Preparing The Antenna Site
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. - Page 12 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.
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Page 13: Calibrating The Meter/Measuring Field Strength
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. - Page 14 2. Set CALIBRATION/FS/SWR 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”...
- Page 15 • 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.
- Page 16 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.
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Page 17: Using Field Strength Readings To Tune Your Radio And Antenna
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 •... - Page 18 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.
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Page 19: Care And Maintenance
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. - Page 20 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.
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Page 21: Schematic Diagram
SCHEMATIC DIAGRAM (illus - show schematic diagram of meter) -
Page 22: Specifications
SPECIFICATIONS Measurable RF Power ........1–1000 Watts SWR ................1–3 Impedance .............. 50 Ohms Frequency Range ..........3–30 MHz × 3 Dimensions (HWD) ...... 2 ¥ 6 Inches (65 ¥ 160 ¥ 100 mm) Weight ................8 oz (226 g) Specifications are typical;... - Page 23 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-...
- Page 24 (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;...
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