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ASK DAVE HAMS PERSEVERING THROUGH ALL SORTS OF ISSUES TRACKING DOWN
INTERMOD Q OUR CLUB HAS BEEN OPERATING A REPEATER FOR OVER 30 YEARS AT THE
SAME LOCATION.  OF LATE, WEVE BEEN GETTING INTERFERENCE THAT HAS GROWN
WORSE.  WEVE TRACED THE AUDIO WERE HEARING TO A COUNTRY MUSIC FM STATION
WHOSE ANTENNA IS NEAR OUR REPEATER.  THEY SAY THERES NOTHING WRONG WITH
THEIR EQUIPMENT.  WHERE DO WE START?  A ITS VERY LIKELY THAT THE FM STATION
IS CORRECT.  FURTHER, THE INPUT FILTERS FOR YOUR REPEATER THE CANS ARE SO
NARROWBAND THAT THEY WILL NOT LET ANY OF THE FM SIGNAL INTO YOUR REPEATER.
THE PROBLEM IS INTERMOD.  THE FIRST STEP IS TO ADD A CTCSS TONE REQUIREMENT
TO YOUR REPEATER INPUT.  THAT WAY, EVERY TIME ONE OF YOUR CLUB MEMBERS
TRANSMITS ON THE REPEATER INPUT FREQUENCY, THEY ARE INCLUDING A SUB AUDIBLE
TONE THAT THE REPEATER MUST HEAR BEFORE IT WILL WORK.  USUALLY, INTERMOD
WILL NOT INCLUDE THIS FREQUENCY.  IF IT DOES, CHANGE THE CTCSS FREQUENCY.
THIS COULD SOLVE THE PROBLEM, AND IS WHAT MANY REPEATER OPERATORS HAVE
DONE.  IF THE INTERMOD BLOCKS LEGITIMATE INCOMING SIGNALS, YOU HAVE MORE
DETECTIVE WORK TO DO.  THE FM STATIONS SIGNAL IS BEING ADDED TO ANOTHER
STATIONS FREQUENCY IN A NON LINEAR DEVICE, AND THE OUTPUT FREQUENCY IS
EQUAL TO YOUR INPUT FREQUENCY.  SUBTRACT THE FM STATIONS OUTPUT FREQUENCY
FROM YOUR REPEATERS INPUT FREQUENCY.  LOOK AROUND FOR A SOURCE OF THIS
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