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Topband: Flag Transformer

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Subject: Topband: Flag Transformer
From: (Mike Knowlton)
Date: Sun, 8 Sep 2002 17:34:30 -0500
 Hi Guys
I'm going to try my hand at putting up a flag for this season. Does any=20
one have one or two Amidon FT140-43 toroids or a good place to order.

   I made a transformer using a 4229 pot core of 3F3 material. I put 13 =
turns on the bobbin for the primary, insulated it and then wrapped a =
brass shield around the winding with out allowing the ends to touch. A =
tab was brought out for connection,this is an electrostatic shield to =
limit capacitive coupling between windings. I cut a Styrofoam clam =
shells to fit around the shield, then wrapped 3 turns around the =
Styrofoam as the secondary. I gapped the core very slightly to have 200 =
ohms impedance at 550 Khz. I soldered a box together using PCB material, =
mounted a UHF connector and brass screws for the antenna connections. =
The brass shield has a separate wire that runs back to the mast and is =
connected to ground.

I have very good nulls so IMHO it seems to have worked very well.


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