Kenji

Testing conditions:
* The distance between TX and RX was about 10 meters

This does seem close, if both were connected to dummy loads there would still be ample signal pickup.

Result of FST4W-300:
* On 7.0388MHz + 1536Hz: undecodable
* On 10.1389MHz + 1536Hz: undecodable
Frequency drift of FT-891?

With a recommended maximum of 0.56Hz for -300 this is quite possible.

The HF+ is quite stable in the short term when warmed up. Using software like Spectrum Lab you can monitor frequency very precisely.

I am not convinced there is any need to use FST4W on the higher frequencies but there may be times that there is an advantage.

73 Alan G4ZFQ