Radio Shack 21-533 Marine Instruments User Manual
Contents
1. 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 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 antenna or antenna mounting system to improve efficiency IZ ZS S 21 533 fm Page 9 Thursday August 5 1999 3 47 PM S IMPROVING SWR There are several ways to improve the SWR of your radio an tenna combination Try these first e 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 e Confirm that you mounted your antenna according to the manufacturer s instructions The angle and the base arrangement can affect the SWR reading e Adjust the length of your antenna according to the instructions provided by the manufacturer A change of as little as s inch can make a measurable difference See your radio s and antenna s owner s manuals 4 TK 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 RF2. 21 533 fm Page 1 Thursday August 5 1999 3 47 PM S Cat No 21 533 OWNER S MANUAL ole Please read before using this equipment CB Ham Field Strength SWR Meter RadioShack E e TK 21 533 fm Page 2 Thursday August 5 1999 3 47 PM 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 transmitters 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 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 precautions provided with the equipment you are test ing Note You need a separate 50 ohm coaxial cable such as RG 58U with a PL 259 connector connected to both ends such as Cat No 278 968 not supplied long enough to reach from your radio s antenna jack to the back of the meter 1998 Tandy Corporation All Rights Reserved RadioShack
3. 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 FS ANT 13 gt 4 TK 21 533 fm Page 14 Thursday August 5 1999 3 47 PM 2 Set CALIBRATION FS SWR to CALIBRATION FS m CALIBRATION FS I 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 e 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 ee Yy a 4 D TK 21 533 fm Page 15 Thursday August 5 1999 3 47 PM e 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 continue
4. 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 e 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 e Make sure there is at least 25 feet of open space in all directions around your antenna 10 a S 21 533 fm Page 11 Thursday August 5 1999 3 47 PM S A a 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 e Antenna Location TK 21 533 fm Page 12 Thursday August 5 199
5. an antenna e Changing the antenna mount on your vehicle e 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 a TK 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 e lf you use a CB that has sideband modes SSB do not select any of these modes Use only AM for field strength measurements e 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 transmit
6. 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 O O ANTENNA TRANSMITTER Vv Vv RadioShack TK 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 _ CALIBRATION FS i 4 xv 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 e 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 gt 40 TK 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 e If you use a CB that has sideband modes SSB do not select any of these modes Use only AM for SWR
7. looking new Do not use harsh chem icals cleaning solvents or strong detergents to clean the meter 19 9 6 TK 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 4 i S 21 533 fm Page 21 Thursday August 5 1999 3 47 PM S SCHEMATIC DIAGRAM a illus show schematic diagram of meter 21 oe i TK 21 533 fm Page 22 Thursday August 5 1999 3 47 PM SPECIFICATIONS Measurable RF Power sssrini 1 1000 Watts SWIRE stad heclih tel ethan oa pep A EE 1 3 Impedance i a REE 50 Ohms Frequency Range esseessssesrssrnesrnerrrnssrrerennernn 3 30 MHz Dimensions HWD 000 2916 65 16 x 315 16 Inches 65 160 100 mm Wight vSiice Fach E EEE 8 oz 226 g Specifications are typical individual units might vary Specifi cations are subject to change and improvement without no tice 22 4 NIA may A 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
8. 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
9. 9 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 a TK 21 533 fm Page 13 Thursday August 5 1999 3 47 PM For example for a 50 foot diameter circle 50 feet 11 46 4 363 Feet So you would place a mark every 4 363 feet 4 feet 3 inches CALIBRATING THE METER
10. A 3A8 Printed in China y
11. 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 NYA ZS Zs 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 triputable 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 811081260
12. is a registered trademark used by Tandy Corporation ae TK 21 533 fm Page 3 Thursday August 5 1999 3 47 PM CONTENTS Measuring SWR 2 0 e cece eee eee eee 4 Connecting the Meter 0 00 c eee eee 4 Calibrating the Meter Measuring SWR 5 Interpreting SWR Readings 8 Improving SWR crpe togini ee 9 Measuring Field Strength nnannnnnnnnnnnnnn 10 Preparing the Antenna Site 11 Calibrating the Meter Measuring Field Strength 13 Using Field Strength Readings to Tune Your Radio and Antenna 00 000 cece ee eee 17 Care and Maintenance 00 eee eee eres 19 Schematic Diagram 0 2 00 cece eee 21 Specifications ss 2 ckipites ha pees is ese 22 3 ar TK 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
13. measurements e 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 p pore 1 FIELD STRENGTH SWR METER 4 Release the transmit key then set CALIBRATION FS SWR to SWR TK 21 533 fm Page 7 Thursday August 5 1999 3 47 PM CALIBRATION FS 1 s 2 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 l S o o S 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
14. s 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 You are Here Dot 15 S 21 533 fm Page 16 Thursday August 5 1999 3 47 PM S 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 TK 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 e Installing a new antenna or antenna cable e Adjusting the length of
15. ter 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 lf 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 a TK 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
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