First Practice FMT Run

A good friend of mine, John WA1ABI, is responsible for planting the FMT bug in my head.  I’ve been admiring his results in the ARRL FMTs for years — he is constantly an outstanding performer.  John graciously suggested that we spend about an hour today having a mini-local FMT on four AM stations plus CHU.  We would each measure/divine the frequency from data collected over a two minute period, shifting to a different spot ever 5 minutes.

Our results were amazingly close, especially with two stations that are known to be high accuracy/stable:  WBZ when in IBOC mode, and CHU.  In fact we were amazingly close on all measurements except for 920 KHz — I probably messed something up.

Anyway, here is the result table.

Station Approximate WB4SON WA1ABI Delta
Callsign Freq in Hz Measured Freq Measured Freq
WBZ 1030000 1029998.807 1029998.807 0.000
WPRO 630000 629998.301 629998.296 0.005
WHJJ 920000 919999.899 919999.863 0.036
WARV 1590000 1589999.431 1589999.427 0.004
CHU 3330000 3330000.005 3330000.006 -0.001

WBZ and CHU were within 1 milliHertz (1 ppb).  WPRO and WARV were within 5 milliHertz (3 ppb).  My oddball was WHJJ which was 36 milliHertz different (39 ppb).

(ED 12/4: John and I captured the audio data from each run and swapped those files for processing on a later date.  He informed me the next day that he analyzed my audio file and would have called the frequency 919999.863 — in other words he thinks my gear was doing fine, but I likely jotted down an incorrect reading.  I wouldn’t be surprised!  When I get a chance I’ll run the audio file through Spectrum Labs and see if I come up with something different than I initially reported.)

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