IN3OTD's web site
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Some Directional couplers:
A 6 dB hybrid combiner from junkbox parts
A homemade hybrid coupler/combiner built several years ago and recently characterized.
A classic 6 dB hybrid combiner design
Wideband hybrid coupler, similar to the classic ARRL Handbook design.
The impedance bridge of the N2PK VNA
Measurements of the 6 dB hybrid coupler used as impedance bridge for the N2PK VNA.
A 20 dB coupler for the HF bands.
Measurements on a 20 dB coupler with low-frequency compensation.