90 degrees phase difference cirquit needed for 1-30MHz

[G4BCH]

Not really. The phase characteristic of the post-mixer filter does not matter. The output of that filter will be in quadrature with the PLL input regardless of the phase at the input of the filter. The accuracy of the quadrature depends only of the phase detector.
Regards

Z

I think we are talking about different things here, the scheme I proposed does not use a PLL to genreate the quadrature.
Atached ( I hope ) is simple block diagram, it says a lot more than a wordy description.
Peter