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7

5 watts is probably what most JT-65 purists will tell you to use, but in practice, I tend to aim for 20 watts. That gives you a good 6dB boost (every doubling of power is equal to +3dB) which is actually meaningful in JT-65. Any more than that, and you'll start finding certain problems. Note that the same is true for the WSPR family of protocols. First, ...


5

As you stated, JT-65 is a weak signal mode. This should not be confused with a low power mode. Depending on your antenna and location, the amount of power you need to conduct a successful contact may vary, just as in any other mode. A good guideline would be to start at the lowest power setting you can, and if you're not able to work the stations you want ...


4

Both modes are FSK, and both have the same effective data rate (72 data bits in about 50 seconds), but there is one very big difference between them: bandwidth. JT9 is 20Hz wide. JT65A (the mode commonly used in HF) is 180Hz wide, JT65B (often used for 2m EME) is 360Hz wide, and JT65C (often used for 33cm and up) is 720Hz wide. Why does this matter and how ...


4

For the current "77-bit" versions of FT8 and MSK144 (as supported by wsjt-x version 2.0, released in late 2018, and newer), you can use these callsigns without doing anything special. Any combination of letters, numbers, and slashes, up to 11 characters total, can be used as a callsign. If your callsign is "nonstandard", meaning that it doesn't follow the ...


3

Knowing when a signal is likely to be present helps the software to decode signals. If signals are of varying lengths, and sent at any time, then it's much harder to decode weak signals that may or not be present. An analogy is the 'old' RS-232 serial data protocol, which could run in 'synchronous' (clocked) or 'asynchronous' modes: knowing from the clock ...


2

Re: "Finally, many transceivers will cause distortions in the JT-65 waveform when run at above a quarter to a half of their maximum power. Transceivers are meant to work with analog data, not the sharp frequency transitions of the digital signal." K1JT has purposefully tailored the audio output of his software so it has none of the effects mentioned above. ...


2

According to K1JT himself, the callsign field is rather restricted and must meet the same parameters as the one for JT65. https://sourceforge.net/p/wsjt/mailman/message/35254350/


1

According to the WSJT system requirements, the time must be synchronized within ±1 second. It's generally the case that the more that is known about a signal, the easier it is to detect. In the case of WSJT, the software records a 4 kHz or so wide swath, and then must find and decode all the signals in it. It must work this way because the nature of the ...


1

According to Wikipedia, JT65 uses 65-tone MFSK (Multiple Frequency-Shift Keying), whereas JT9 uses 9-tone FSK (Frequency-Shift Keying); probably hence the numerals in the respective names. By only ever transmitting exactly one out of a set of fewer tones, it would appear intuitively that JT9 would be better suited to the variable signal strength commonly ...


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