GB3VHF for frequency calibration and 28MHz operation

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Last seen: 2 years 4 months ago
Joined: 2009/12/07 - 18:03
GB3VHF for frequency calibration and 28MHz operation

During my first month using WSPR, mainly on 28MHz, I have been amazed at the spread in frequencies that are reported for my signals. I am lucky that all my FT-897D oscillators are locked to a single TCXO, and that I can tune this to GB3VHF (which I believe is GPS-locked to 144.430MHz). Using a waterfall audio utilty I can achieve error <5Hz at 144.430MHz, and so hopefully <1Hz at 28MHz. The biggest problem in the tuning is that stiction in the trimmer makes it difficult to make small adjustments. There may also be a small error in the clock frequency of my audio card but at 1kHz this ought not to be much. (Tests with three different PCs all agree within +/-1Hz at 1,000Hz).

Yesterday my signals were spotted by two G-stations, first with a frequency error of 90Hz and 88Hz, and later with an error of 48Hz. The error from the first station is nearly half the width of the WSPR band! Anyone operating with such an error will miss many transmissions and have theirs missed too. GB3VHF can be heard over much of the UK, and a waterfall utility with fine resolution can be used at very weak signal strengths so it is an easy check. I'm usually on 28.126077MHz. If you spot me anywhere else try a check with GB3VHF, and if you think my frequency is wrong please tell me. It is important for the quiet bands that we all have good frequency alignment.