26 Jan 2017

2m WSPR frequency stability

Most users (including me!) have real issues with accurately getting to, and staying on, frequency with 2m WSPR. The WSPR slot is just 200Hz wide and the short-term and long-term rig drift can be a real problem. With WSJT-X v1.7 one can see most stations drifting wildly.

Last night I was greatly helped by David G0LRD who uses a GPS stabilised frequency reference, so he knows his frequency very accurately. He is also very strong with me, so I could see his signal clearly. All I had to do was net my rig so I was reporting to WSPRnet his correct frequency on RX. I did this late last night. My rig had to be set 20Hz low (144.488980MHz) to get G0LRD as close as possible. Of course, during the night I drifted off again, but in the short-term I knew I was on the correct window in the 2m band.

Longer term, the answer is a more accurate, and stable, frequency reference. Ideally this would be a GPS locked source. An accurate TCXO would be an affordable second best.

I was very grateful to G0LRD last night.  Incidentally, David put up my 2m antenna some time ago. Kindness itself - thank you David!

I've now QSYed to 10m JT65 for the day.

1 comment:

Hugh said...

One of the biggest problems is the rig heat-up during Tx, causing banana-shaped traces. The long term drift can be corrected and compensated, but these short-term drifts are more difficult. They can, however be considerably reduced, by the simple action of thermally isolating the PLL reference frequency crystal. This can be as simple as a little expanded polystyrene hat, popped over the metal can, which stops the hot air inside the rig during Tx heating up the crystal so quickly. I don't know if this is easy to do for the FT817, but it really helped my setup. Hope this helps, Regards, Hugh.