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[TowerTalk] Flag Antenna Transformer

To: "Towertalk" <>
Subject: [TowerTalk] Flag Antenna Transformer
From: "Tony Brock-Fisher" <>
Date: Sun, 29 Jan 2012 11:52:45 -0500
List-post: <">>
I have a flag antenna which has worked well for several years. I used a 
Minicircuits T16-6 transformer to couple the ~800 ohm termination resistance of 
the antenna to 50 ohm line. Recently I decided to do some upgrades, so I 
followed the recommendations of many (here and elsewhere) and made a matching 
transformer using an FT-140-43 core and 34:8 turns, secondary and primary on 
opposite sides of the core. I didn't have any #28 wire so I used #24. I tested 
this with a miniVNA, terminating the antenna side with an 800 ohm noninductive 
resistor. The impedance does not look right at all; there is a lot of inductive 
reactance and the resistive part starts at 125 ohms and climbs steeply from 1.7 
MHz. No on-the-air results yet.

I'm wondering if this is right or not - measurements indicate the DIY 
transformer is much worse than the T16-6 in terms of presenting a good match. 

This would not be the first case of theory saying it won't work but practice 
says it will - just looking for a reality check here. Seems to me like the core 
material is all wrong...

-Tony, K1KP

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