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Category: Test & measurement
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      This is a return loss bridge based on N6JF design. I use 2 100 ohm 1W metal film in parallel for the 50 ohm resistors permitting up to 8W power input. I use a FT37-43 Amidon core with 10 bifilar turns. The range is about 1 MHz to 1 GHz but it is practical from 1.8 up to 500 MHz. A 5*5 cm metal box is used. I use BNC but SMA is recommended as BNC do not make good contact occasionally. A small PCB was soldered under the components simulating a stripline.

Frequency MHz Directivity dB
1 30
1.8 35
3.5 40
7 42
10 45
29 50
144 50
435 35
900 25