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.
|Callsign||Freq in Hz||Measured Freq||Measured Freq|
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.)