tuckvk3cca,
Thanks for the feedback. I finally was able to find a directivity specification of 20 dB minimum for the Narda 3060-20 on the web, which is in agreement with my measurement made using the nanoVNA. My best directional couplers have a 40 dB directivity. The ones I own with a directivity below 20 dB I only use for indicative purpose.
