A few issues about JT65-HF.
First and most important is that of time synchronization. You cannot successfully have a JT65 QSO without a close synchronization of your local computer's time value to UTC. Period. End of discussion. I use Dimension 4 for synchronization.
The built in time synchronization software with Windows XP (and beyond) is usually not sufficient to maintain a high degree of accuracy. Trusting those methods will likely leave you routinely out of temporal sync and make your enjoyment (and others as well) of JT65 much lessened.
If you do not have internet access your only option is to try to maintain a manual sync by some broadcast time service. If you can get (and maintain) accuracy within +/- 1 second of UTC you should be able to work other stations. The closer to perfect the better. Do not assume your PC's clock is stable. Many have highly inaccurate clocks that gain/lose time at a substantial rate. Considerations for transmitting JT65.
JT65 is indeed an FSK mode in that it transmits distinct single tones from a tone set of 65 values. JT65 is NOT TRANSMITTED using FSK. It uses AFSK and this is a critical distinction. Avoid ALC action if possible with an AFSK signal. Much like any other audio input to an SSB transmitter JT65 can generate a poor signal if over driven.
JT65 is a weak signal mode. Its primary purpose is to facilitate EME (Earth->Moon->Earth) communications. For use on HF you need to re-think your power levels. Often a few milliwatts will do amazing things. Some situations call for much higher power levels, but in day to day HF usage, 10 to 20 watts is probably enough, if not too much.
[Source: Joe – W4CQZ ex W6CQZ]
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