This morning I found the DX station on 30m JT65 mode.
That DX station QRV on 249Hz. This mean that USB mode can used JT65 mode. So Transceiver indicated carrier point frequency. Normally 10138.00KHz.
That 249Hz mean is JT65 signal frequency. Normally SSB signal band width as same as voice frequency width. Therefore 300Hz to 3000Hz is standard frequency width.
However, that DX station used 249Hz that it value is out of voice frequency width. So it cannot send JT65 signal.
However, I used IC-7700 transceiver. This transceiver set the transmitted frequency width. Because this transceiver used DSP system. So easy setup TX or RX frequency range.
Therefore I set up on 100Hz for lower transmitter frequency of my IC-7700.
I QSO for that DX station.
I think, the popular transceiver cannot change the TX frequency range. It fix to 350Hz to 2700Hz. Therefore normally cannot use under 350Hz frequency, I think so.
What do you think? Correct or not.