‰ NOW 40 WPM ‰ TEXT IS FROM AUGUST 2012 QST PAGE 47‰ LOSS IS 12 ON THAT BAND. DETAILS OF MY TEST SETUP ARE AVAILABLE IN THE DIGITAL EDITION OF QST AND ONLINE AT WWW. ARRL. ORG/QST IN DEPTH. MFJ 994BRT REMOTE AUTO TUNER THE MFJ 994BRT, WITH ITS 600 W SSB/CW CAPABILITY, IS PERFECT FOR THE MANY MEDIUM POWER AMPLIFIERS ON THE MARKET. THE PHOTOS ACCOMPANYING TABLE 2 SHOW THE OUTSIDE OF THE UNIT AND THE INTERNAL CIRCUITRY. NOTE THAT THE INDUCTORS CONSIST OF A MIX OF TOROIDAL AND WIDE SPACED AIR WOUND INDUCTORS. ARRL LAB TE NETWORK DESKTOP AUTO TUNERS. TURNING THESE INTO REMOTE AUTO TUNERS INVOLVED MOUNTING THEM IN WEATHERPROOF BOXES AND REMOVING SOME OF THE DESKTOP FEATURES SUCH AS A/B ANTENNA SWITCHING AND MULTIPLE MEMORY BANKS. A COMPARISON OF THE MFJ994BRT AND MFJ 998RT AUTO TUNERS IS GIVEN IN TABLE 1. IN ADDITION TO THE HIGHER RF POWER RATINGS, THE MFJ 994BRT AND MFJ 998RT INCLUDE SOME INTERESTING FEATURES NOT FOUND IN OTHER REMOTE AUTO TUNERS. THE FIRST IS AN INTERNAL BIAS T FOR THOSE WHO MAY NOT HAVE DC POWER AVAILABLE AT THE ANTENNA. A BIAS T ALLOWS YOU TO INJECT DC INTO THE COAX FEED LINE SO YOU DONT HAVE TO RUN A SEPARATE POWER CABLE. AN MFJ 4117 BIAS T FOR THE STATION END OF THE FEED LINE IS INCLUDED WITH BOTH UNITS AND IT INCLUDES AN ON/OFF SWITCH FOR CONVENIENT POWER CONTROL OF THE AUTO TUNERS. THE MFJ 994BRT AND MFJ 998RT PROVIDE SO 239 CONNECTORS AND RANDOM WIRE OUTPUTS ONLY ONE AT A TIME CAN BE USED. THE SO 239 CONNECTOR HAS BEEN TESTED TO MORE THAN 2 KV TO ENSURE THERE IS NO POSSIBILITY OF ARCING UNDER HIGH SWR CONDITIONS. THESE AUTO TUNERS INCLUDE AN LC LIMIT FEATURE THAT PROVIDES UPPER LIMITS OF INDUCTANCE AND CAPACITANCE ACCORDING TO FREQUENCY PRODUCT REVIEW MFJ 994BRT AND MFJ 998RT REMOTE AUTOMATIC ANTENNA TUNERS THESE HIGH POWER MATCHING NETWORKS MOUNT AT THE ANTENNA. REVIEWED BY PHIL SALAS, AD5X CONTRIBUTING EDITOR AD5X ARRL. NET I PREVIOUSLY REVIEWED SEVERAL REMOTE AUTOMATIC ANTENNA TUNERS SPECIFICALLY FOR USE WITH A 43 FOOT VERTICAL ANTENNA. THOSE REMOTE TUNERS WERE LIMITED TO ABOUT 200 W MAXIMUM RF POWER, UNSUITABLE FOR STATIONS USING POWER AMPLIFIERS. THIS HAS NOW CHANGED WITH THE INTRODUCTION OF THE MFJ 994BRT 600 W AND MFJ 998RT 1500 W REMOTE AUTO TUNERS. A REMOTE ANTENNA TUNER MUST BE WEATHERPROOF AND REMOTELY POWERED, AND IT MUST PROVIDE AUTOMATIC TUNING. FOR A GIVEN RF POWER HANDLING AND IMPEDANCE MATCHING SPECIFICATION, A REMOTE ANTENNA TUNER WILL GENERALLY BE MORE EXPENSIVE THAN A DESKTOP UNIT BECAUSE OF THESE REQUIREMENTS. WITH MANY MANUAL AND AUTOMATIC DESKTOP MODELS AVAILABLE, WHY USE A REMOTE ANTENNA TUNER? ITS AN EFFICIENT WAY TO MATCH AN ANTENNA THAT HAS A HIGH SWR AND IS FED THROUGH A RELATIVELY LONG LENGTH OF COAXIAL CABLE. SWR RELATED COAX CABLE LOSSES CAN BE HIGH WHEN THE ANTENNA SWR IS HIGH EVEN IF AN IN SHACK TUNER PROVIDES A 1 1 SWR FOR YOUR EQUIPMENT. YOU CAN EASILY DEMONSTRATE THIS WITH ANTENNA MODELING SOFTWARE SIMULATIONS AND A COAX/SWR CALCULATOR. OVERVIEW THE MFJ 994BRT AND MFJ 998RT ARE REMOTE VERSIONS OF THE CURRENT MFJ 994B 600 W AND MFJ 998 1500 W SWITCHED L ‰ END OF 40 WPM TEXT ‰ QST DE W1AW ƒ