Hi Hiro san,
So now you successfully installed v1.27.3, congratulations!
Perhaps you want to install v2.02 as next step?
In Europe we sometimes have a lot of interference (especially in the evenings) from some shortwave broadcast stations that are operating in 41m band. The strong signals can mix with some harmonics of the BFO frequency. As a result the mixer products (image signals) are appearing in the 40m amateur band.
But it happens only in LSB mode.? If we switch to USB mode, then the interference is disappeared.
The reason is that in LSB mode, the VFO is set to 5 MHz, in USB it is at 19 MHz (other side of IF).
Do you have this problem also in Japan?
If you have this problem then v2.02 software could fix it.
Because in v2 software we set the VFO always to 19 MHz (for both LSB and USB mode).
When the VFO is at the high side of the IF then the mixer products will be outside the 40m band.
For v2 an extra small modification (digital BFO mod) is required:
You will have less interference from broadcast stations and also less "birdies".
73 Allard PE1NWL
Allard PE1NWL