Confusion: Dishal Tuning Method for Coupled Filters

Reference article was published in 1951. At this time no VNA or HFSS existed but signal generators and detectors. Tuning method is useful for preliminary tuning of filter and final tuning is done in iteration manner. Today such filter is tuned by using scalar or vector network analyzer which shows how particular filter resonator is tuned and off course overall response.
Simulation of this tuning method has no sense.

@Borber

I was thinking of simulation to know what to expect when doing it practically.

Anyways, can you share the practicalities of tuning this filter on a VNA? I mean what will I be doing and what will I be looking for.

i have not done it in a while, so I do not recall the details.

But I do remember you look on a VNA at the complex S11. You start off with all the bandpass filter's resonators shorted (either with a tuning screw or tiny wire soldered on). Then you tune the first resonator (the one closest to Port I) by un-shorting it and tuning until its phase is something (zero degrees as I recollect).

Then when it is tuned, you break the short circuit at the 2nd resonator. Then when it is tuned, you break the short circuit at the 3rd resonator. And so on.

Once the last resonator is tuned, you can THEN look at detected power at Port II and see the filter shape in the S21 amplitude measurement.

At that point you can go back and screw around with the coupling capacitors until the S11 is good AND the S21 width is correct.

As I recalled, I set the initial VNA reference plane by putting a tiny short at the input coupling capacitor, adjusted the ref plane extension until I got 180 degrees, then removed it to begin the tuning process.

Thank you very much, biff44, for the reply.

Reading your post, I can form out some steps as follows. Kindly correct me if I am wrong somewhere.

1) Connect filter's input to VNA port-1 and output to VNA port-2
2) Short out every resonator using tuning screws and set reference plane of phase of s11
3) Tune first resonator near to port-1 to get 0 degrees on VNA
4) Tune 2nd resonator to get (0 or 180) degrees? (Here I am confused because of the data I read in ref. paper to get alternate maximas and minimas. Please clarify)
5) Repeat till filter is tuned

yeah, the only thing I am not sure of is the zero degrees on part 3), but I think it is correct. Then in 4), tune the other resonators to what you used in 3) for phase.

I am pretty sure it is zero degrees, since a L-C resonator, if tune to resonance, is an open circuit at resonance, hence a S11 angle of zero (like an open circuit)

Thank you biff44.

I will try the procedure now. Lets see if I am successful or not.