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Radio Shack 21-533, Owner'S Manual

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Radio Shack 21-533 Owner'S Manual Download Page 4

4

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.

21-533.fm  Page 4  Thursday, August 5, 1999  3:47 PM

Summary of Contents for 21-533

Page 1: ...Cat No 21 533 OWNER S MANUAL Please read before using this equipment CB Ham Field Strength SWR Meter 21 533 fm Page 1 Thursday August 5 1999 3 47 PM ...

Page 2: ...d power The meter s field strength function helps you position your antenna for the best coverage and determine the effective ness of changes you make to your antenna antenna cable and transmitter Carefully read all of these instructions to get the best use from this meter Warning You can use this meter to make measurements on equipment that uses high voltages Carefully observe all safety precauti...

Page 3: ...eadings 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 21 533 fm Page 3 Thursday August 5 1999 3 47 PM ...

Page 4: ...er 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 antenn...

Page 5: ...ER 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 21 533 fm...

Page 6: ...el 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 21 533 fm Page 6 Thursday August 5 19...

Page 7: ...R 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 SWR Scales 21 533 fm Page 7 ...

Page 8: ...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 Very good The antenna the cable and the transmitter operate very efficiently 2 0 to 3 0 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 a...

Page 9: ... 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 as little as 1 8 inch can make a measurable difference See your radio s and antenna s owner s manuals 21...

Page 10: ...ength 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 obj...

Page 11: ...ield 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 21 533 fm Page 11 Thursday August 5 1999 3 47 PM ...

Page 12: ...osely 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 mor...

Page 13: ...TER 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 21 533 fm Page 13 Thursday August 5 1999 3 47 PM ...

Page 14: ...e 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 o...

Page 15: ... 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 Dot You are Here Direction of ...

Page 16: ...e 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 21 533 fm Page 16 Thursday August 5 1999 3 47 PM ...

Page 17: ...ength 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 ...

Page 18: ...io 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 ...

Page 19: ...r 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 occasionall...

Page 20: ...nts 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 21 533 fm Page 20 Thursday August 5 1999 3 47 PM ...

Page 21: ...21 SCHEMATIC DIAGRAM illus show schematic diagram of meter 21 533 fm Page 21 Thursday August 5 1999 3 47 PM ...

Page 22: ...hms 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 21 533 fm Page 22 Thursday August 5 1999 3 47 PM ...

Page 23: ...CIDENTAL 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 sal...

Page 24: ...ltage 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 ...

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