NEC-LIST: Waveguide modeling

What is the correct way to model a 1/4 mono pole in a circular waveguide?
Ive already seen W1GHZ's example but its for a model using surface patches
and im using GW's.

Take the following for example..
Waveguide diameter is 9cm
1/4wave is 3cm

The bottom of the "mouth" of the waveguide opening is -4.5, the top is 4.5 in
(z coord)
Should the monopole GW go from -4.5 to -1.3 (3cm) and with how many segments?
Such as http://207.22.18.52/~mikes/waveguide2.jpg but this has awefull VSWR
20:1

Also ive seen it done this way, with good vswr, but it doesnt make sense to
me.

GW 1 1seg from -4.5 to -4.3 (z coord)
GW 2 1seg from -4.3 to 1.3 (z coord)
EX on GW 1

picture for reference
http://207.22.18.52/~mikes/waveguide1.jpg

Now i dont understand this because your EX'ing a 2mm wire that is joined with
the 1/4 wave
wire. And the excited wire is also shorted with the can. But this results in
VSWR under 2:1

Could someone tell me the proper way to model a 1/4 monopole in a waveguide?

Mike Spenard

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