I have been wanting to try some simple collinear antennas for a while now.
The gain is supposed to be between 5.8-6db.
It's quite simple to construct.
measure 60mm from feed point to the first loop, than measure 90mm from the bottom of the first loop and make a second loop in the same direction as the first one, than leave 83mm for the top section.
If you do this the best swr you'll get is 1.4 to 1.5.
If you want better SWR, cut a 1/4 wavelength section of wire (slightly abundant) and solder either on the sma connector or directly on the outer braided sock of the feed line, approx about half wavelenth south of the feed point.
Than with a swr meter bend the "pseudo-radial" down some 20° until you hit 1.1 SWR.
These are the antennas.