25-11-2018, 09:01 AM
Hi Colin,
I have seen similar signals when using both FT8 and JT65, to me they look like expanded 'birdies' or 'harmonics' from strong signals some where lower in frequency - on your image, possibly at ~ 630hz. This was most evident when using JT65, as with its wider signal width I could see the individual element pattern being reflected further up the waterfall.
The cause, maybe over-driven/over-modulated TX signal, or some interaction in the receive path, they always seem (to me anyway) to be associated with strong signals.
Just my observations on the signals.
73 Andrew
I have seen similar signals when using both FT8 and JT65, to me they look like expanded 'birdies' or 'harmonics' from strong signals some where lower in frequency - on your image, possibly at ~ 630hz. This was most evident when using JT65, as with its wider signal width I could see the individual element pattern being reflected further up the waterfall.
The cause, maybe over-driven/over-modulated TX signal, or some interaction in the receive path, they always seem (to me anyway) to be associated with strong signals.
Just my observations on the signals.
73 Andrew