CB/Ham Field-Strength SWR Meter - RadioManual

1 Cat. No. 21-533 OWNER S MANUALP lease read before using this field -StrengthSWR Page 1 Thursday, August 5, 1999 3:47 PM 1998 Tandy Rights is a registered trademark used by Tandy RadioShack CB/Ham Field-Strength SWR Meter helpsyou tune your CB or amateur radio system for the best and amateur radio systems work best when the antennasystem s impedance matches the transmitter s output im-pedance as closely as possible. The Meter s standing waveratio (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 yourantenna for the best coverage and determine the effective-ness of changes you make to your antenna, antenna cable,and read all of these instructions to get the best usefrom this : You can use this Meter to make measurementson equipment that uses high voltages.

2 Carefully observe allsafety precautions provided with the equipment you are : You need a separate 50-ohm coaxial cable (such asRG-58U) with a PL-259 connector connected to both ends(such as Cat. No. 278-968, not supplied), long enough toreach from your radio s antenna jack to the back of Page 2 Thursday, August 5, 1999 3:47 PM3 CONTENTSM easuring 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 Radioand Antenna.

3 17 Care and Maintenance .. 19 Schematic Diagram .. 21 Specifications .. Page 3 Thursday, August 5, 1999 3:47 PM4 MEASURING SWRM easuring SWR shows you how much of your radio s transmitpower 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 soyour antenna and radio combination can produce the maxi-mum power they are capable of more information about measuring SWR, see the ARRLH andbook, available at your local THE METERTo connect this Meter to your CB or amateur radio and yourantenna, you need RG-58U coaxial cable (not supplied) witha PL-259 connector on both ends (such as RadioShack 278-968).

4 The cable must reach from the back of themeter to your radio s antenna these steps to connect the Meter to your radio and Page 4 Thursday, August 5, 1999 3:47 PM51. Turn off your radio. Then disconnect the antenna fromthe radio and plug it into ANTENNA on the back of Plug the coaxial cable into the radio s antenna jack andinto TRANSMITTER on the back of the THE Meter /MEASURING SWR1. Set CALIBRATION/FS/SWR on the front of the Meter Turn on your radio. Then select a channel or frequencyon your transmitter and hold down its transmit key. Do notspeak into the : An SWR reading will be different for different frequen-cies (channels).

5 If you transmit on one channel moreoften than any other, select that channel. If you Page 5 Thursday, August 5, 1999 3:47 PM6mit on several channels, choose a frequency in themiddle of the range of channels you use. (For example,if you transmit on all 40 CB channels, choose Channel20, because it is midway between Channel 1 andChannel 40.) If you use a CB that has sideband modes (SSB), do notselect any of these modes. (Use only AM for SWRmeasurements). If you have an amateur radio, select the continuouswave (CW) or tuning mode to check the While you hold down the transmit key, rotate the Meter sknob until the needle points to Release the transmit key, then set CALIBRATION/FS/SWRto Page 6 Thursday, August 5, 1999 3:47 PM75.

6 Press the transmit key again, then read the SWR by not-ing the needle s position on the upper SWR scale. Ameter reading of 1 on the upper scale is figure shown between the upper and lower scales onthe Meter (% REF POWER) indicates the percentage ofpower that is wasted through reflection of the signal fromthe antenna back into the antenna cable. For example,an SWR reading of also means that 4% of your signalpower is lost. However, 96% of the radio power is morethan enough for almost all Repeat Steps 1 5 for each channel or frequency youwant to get an SWR reading Page 7 Thursday, August 5, 1999 3:47 PM8 Interpreting SWR ReadingsAn ideal SWR reading is , but this reading is usually possi-ble only under laboratory conditions or with a dummy load.

7 Ac-tual antenna installations have higher readings. The in-formation below will help you interpret the readings you to antenna cable and the antenna length match the transmitter s output require-ments almost to goodThe antenna, the cable, and the transmitter operate very to antenna, the cable, and the transmitter operate with some loss. If possible, adjust your antenna or antenna mounting system to your antenna or antenna mounting system to improve Page 8 Thursday, August 5, 1999 3:47 PM9 IMPROVING SWRT here 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 foryour equipment.

8 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 themanufacturer s instructions. The angle and the basearrangement can affect the SWR reading. Adjust the length of your antenna according to theinstructions provided by the manufacturer. A change ofas little as 1/8 inch can make a measurable difference. See your radio s and antenna s owner s Page 9 Thursday, August 5, 1999 3:47 PM10 MEASURING field STRENGTHYour 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 patternof your antenna, or to compare your radio and antenna s effi-ciency before and after an adjustment.

9 You do not need to con-nect the Meter to the antenna or the radio to measure fieldstrength. It takes two people to measure field strength . For an accuratemeasurement, you will need to map the site around your anten-na. Then, while someone presses the radio s transmit key, youwill need to walk around the site around your antenna with themeter, marking the readings you : 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 alldirections around your Page 10 Thursday, August 5, 1999 3.

10 47 PM11 PREPARING THE ANTENNA SITEB efore you use the Meter to measure field strength , you shouldmark the site around the antenna in a pattern that will help youmake the easy way to do this is to map the area around your antennausing a template like this Page 11 Thursday, August 5, 1999 3:47 PM12 The template shows an imaginary circle around an spokes on the template represent imaginary straight linesmeasured from the center of the circle to 36 points spacedequally around the circle. Each straight line is 25 feet in numbers on the template (1 5) are a guide to show youwhere to mark the field strength level the Meter displays as.