Who made this old 13cm helix antenna?

[G4GHD]

I bought two of these at a rally long ago, circa 1998 I think. Am interested to know who made them and what their full spec was, should anyone know.

[G1LPS Terry]

sandpiper I had two. Never found them very good. had a claimed gain of 15db Circular (12db if rxing H)

[G4GHD]

Thanks, did think it might be Sandpiper, but wasn't sure. I used one at the time on rx only and it seemed okay, but was never able to ascertain its performance.
I recently tested it on a NanoVNA v2 Plus4 and the results weren't what I expected, although I need to do more tests to clarify things.

[G0NMY]

I have two of them, only used to receive the copper chopper back in the day.
I think there was a mod to improve the match using a tapered piece of copper at the feed point, although I never tried it myself.
Hmm I would be interested in if they could be used for QO-100 NB maybe?

[G4GHD]

I used one of mine, fixed on London, for the same purpose, but it was obviously not as good as the JVL loop yagi I'd used previously, even allowing for the non-optimal set up.

A VNA test on mine just now, one is fairly good in terms of SWR/Return Loss, but the other (which has slightly smaller dimensions, but still sold as a 13cm ant), isn't so good. Both can be 'improved' in terms of matching at least, by crude use of hand capacity by the feed point, so I'll be interested to hear of the mod. should anyone know of the details.