‰ NOW 40 WPM ‰ INFORMATION ABOUT USING THIS TYPE OF INSTRUMENT. IN ADDITION, A SEARCH OF THE QST ARCHIVES ON THE ARRL WEBSITE BRINGS UP A NUMBER OF ARTICLES ABOUT FIELD STRENGTH METERS, AND THERE IS A BRIEF DISCUSSION IN THE ARRL HANDBOOKS TEST EQUIPMENT AND MEASUREMENTS CHAPTER. NEW PRODUCTS SIGTRAX SIGNAL TRACKING APP FOR IOS AND ANDROID AMCEPT, LLC, OF BIRMINGHAM, ALABAMA, ANNOUNCES THE GENERAL AVAILABILITY OF SIGTRAX VERSION 2, ITS SIGNAL TRACKING APP FOR IOS AND ANDROID QRPGUYS DIGITAL FIELD STRENGTH METER KIT REVIEWED Y PAUL DANZER, N1II N1II ARRL. NET A FIELD STRENGTH METER DOES EXACTLY WHAT THE NAME IMPLIES SENSES THE STRENGTH OF AN RF FIELD AND GIVES A RELATIVE VALUE ON THE DISPLAY. FIGURE 10 SHOWS THE SCEMATIC FOR A CLASSIC FIELD STRENGTH METER THAT IS SIMPLY A DIODE DETECTOR CONNECTED TO AN ANALOG METER. THE STRONGER THE FIELD, THE HIGHER THE METER WILL READ. AS YOU MIGHT GUESS, THE DESIGN WAS NOT VERY SENSITIVE. THE METER WOULD NOT READ ALMOST UNTIL THE INHERENT VOLTAGE DROP ON THE GERMANIUM DIODE 0R25 TO 0R3 V WAS RECEIVED. FROM THERE, YOU COULD GET A METER READING. ALTHOUGH IT WAS USEFUL IN STRONG FIELDS, IT GAVE NO INFORMATION IN WEAK FIELDS. A MODERN DESIGN THE QRPGUYS FIELD STRENGTH METER KIT REVIEWED HERE USES AN ANALOG DEVICES AD8307 LOGARITHMIC AMPLIFIER, AN LM358 OP AMP, AND A DIGITAL DISPLAY TO CREATE A SENSITIVE, MODERN FIELD STRENGTH METER. IT IS RATED TO SENSE A SIGNAL AS WEAK AS 80 DBM, WHICH IS THE EQUIVALENT TO AN INPUT, IF DIRECTLY CONNECTED AS A 50 LOAD, OF 10 PICOWATTS 0R00001 MICROWATTS. AT THE HIGH END OF THE RANGE, THE MAXIMUM SIGNAL INPUT IS 16 DBM 40 MILLIWATTS OR 1R41 V, BUT THE UNIT SHOULD NOT BE USED AS A POWER METER. YOU MIGHT DAMAGE IT IF CONNECTED DIRECTLY TO AN RF VOLTAGE AT THE HIGH END OF ITS RANGE. PACKAGED ON A 2R4 X 2R7 INCH PRINTED CIRCUIT BOARD, THIS DEVICE IS POWERED BY A 9 V BATTERY. IT USES A SLIDE SWITCH TO TURN IT ON CONTINUOUSLY, AND ALSO HAS A PUSHBUTTON SWITCH THAT HOLDS IT ON AS LONG AS YOU PRESS THE BUTTON. THE GREEN LED SHOWS POWER ON. THERE ARE TWO INPUT PORTS, A STANDARD BNC CONNECTOR, AND AN SMA CONNECTOR FOR THE INCLUDED FLEXIBLE ANTENNA. RELATIVE FIELD STRENGTH IS SHOWN ON A THREE DIGIT DISPLAY MODULE WITH A RED FILM COVER. ASSEMBLING THE KIT THE QRPGUYS WEBSITE RATES DIFFICULTY AS A 3 TO 4 ON A SCALE OF 5 AND SUGGESTS ALLOWING AN HOUR FOR THE BUILD. THE WELL ILLUSTRATED, EIGHT PAGE INSTRUCTION MANUAL IS AVAILABLE FOR DOWNLOAD FROM THE QRPGUYS WEB SITE. YOU WILL NEED THE USUAL TOOLS A 40 W SOLDERING IRON AND THIN SOLDER, FLUSH CUTTERS, AND A MAGNIFIER. A FIXTURE TO HOLD THE PC BOARD IS ALSO HELPFUL. THERE ARENT MANY PARTS TWO CONNECTORS, TWO SWITCHES, A PRE WIRED DIGITAL DISPLAY, TWO SOLID STATE DEVICES, AND A FEW RESISTORS AND CAPACITORS. IN ADDITION TO THE SUPPLIED INSTRUCTIONS, HERE ARE TWO ADDITIONAL SUGGESTIONS. FIRST, INSERT THE EIGHT PIN LM358 IC INTO ITS SOCKET JUST BELOW THE BNC CONNECTOR BEFORE MOUNTING THE CONNECTOR. NEXT, THE PUSHBUTTON SWITCH IS NOT ‰ END OF 40 WPM TEXT ‰ QST DE W1AW ƒ