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[TowerTalk] PI Network ATU

Subject: [TowerTalk] PI Network ATU
From: Roger Parsons <>
Date: Sat, 6 Nov 2004 23:57:46 +0000 (GMT)
List-post: <>
Can anybody help me with a definitive method for
adjusting a PI Network ATU?

The unit that I have is an ex-military
motorised/preset tuned one. It has a 50:200 Ohm WB
transformer at the input. Input and output
capacitances are set using cam operated switches, and
the coil can be tapped where appropriate.

The problem that I have is that it is difficult to set
the capacitance values when any particular band is
selected - one has to move it to another band so that
the cams can be adjusted. This involves going back
into the shack to switch it as it is remote operated.
I have tried guessing input and output capacitance
values and then moving the coil tap (which can be done
while it is tuned inband) for lowest SWR. Trouble is
that I've mostly guessed wrong and it's going to take
forever to get it set up.

Any thoughts (apart from 'scrap it') please?

73 Roger

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