90 degree phase shift circuit help

[AdrianH]

This is part of the circuit from a TS100/AP radar test scope? I have a little bit of other information on the unit such as part in pdf.

What I am wondering is how I could wind the phase shifting assembly, it is shown as 6 coils with the centre two in series as part of a resonant circuit in the anode of V7b. and groups of two coils centre fed with HT for X and Y sections both resonant one above and one below centre frequency.

I would like to try and wind such a coil if possible on a ferrite rod, but I am not sure of the sense of the centre winding for it to work, I am hoping that even though it is shown as split it could be wound as one winding.

I can not fathom why it provides a 90 degree shift between X and Y, other then note one set of deflection coils is set above and the other below centre frequency so I am assuming one coil will provide a leading voltage the other a lagging voltage, but why? I never was good at theory.

Any simple explanations gratefully accepted as to information on winding such a coil. This is a bit of fun to provide a circular trace on one of my CRT's at a fixed rate, I have a 81KHz crystal on it's way after the festive season. But would like to see if this could also be done at AF frequencies (using valves and transformer!).

The last bit I find hard to understand is the text says that X and Y deflection plates have equal amplitudes, but as deflection plates on the 3DP1 have different sensitivities how does that work to produce a circle?


I understand more by building not reading I think.

Adrian

[AdrianH]

It is amazing what sleep can do to the brain. As it is talking of resonant frequencies then they must all be wound in the same sense on the same former, providing I can make them resonant just above and below the correct frequency it should work.

Adrian