Topband: Beverage transformers

[Tom Rauch]

If you use 73 material cores about 1 or two inches of stack height, 
a two turn primary is enough for 75 ohms. It is the area inside the 
core exposed to the wire and the number of turns that mainly 
controls impedance in a given core material.

I use a two turn primary and five turn secondary of 75 ohm 
primaries, and the transformers are good from below the BC band 
to over 30 MHz with very low loss and a flat SWR.

A two turn primary and six turn secondary works for 50 ohm 
feedlines.

I keep the secondary isolated from the primary, to prevent the 
feedline from being part of the antenna system.


73, Tom W8JI
w8ji@contesting.com



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