I am not aware of this on other bands but on several stations I am giving WSPR reports to the same station at the same time but at several frequencies separated by 50Hz or 100Hz from the main response. I am not aware of this being an issue on other bands or an issue on TX.
Most recently I saw the issue with ON7KB and with G4BOO earlier. The issue seems to be with my end and not a TX fault. It is not as if signals are that strong, for example the strongest from ON7KB was -13dB S/N. As I have not seen this before and as I am a "transient" 160m visitor I am not keen to start pulling things apart.
Anyone else seen this? I use a SignaLink USB to interface the FT817 to the PC. Maybe I have some RF getting into the heavy duty linear PSU I am using and this only happens on 160m?
For example, I have never seen the issue on 630m (472kHz) WSPR with the same FT817, same PC interface via the same SignaLink USB. Tonight I am not on 472kHz as I am using the kit on 160m WSPR.
I intend to stay on 160m overnight using the earth-electrode "antenna".