Dear Satellite enthusiasts,
i recently read in cq/dl ham magazine about a circular polarized (CP), omni directional cross-dipole (aka turnstile) covering 12m and 10m and everything in between.
Looking at the frequency range of 5 MHz, I was very sceptical. But with all the required hardware handy, i gave it a try. No tinkering at all, just built per the article, my antenna analyzer confirmed a good , flat match over the entire range from 24.9 to 29.7 Mhz with a perfect match somewhere around 26.7MHz. This is a contradiction to the statement in ROTHAMMEL antenna book, where turnstile antennas are described as narrow band antennas. Anyway, with the dimensions given in cq/dl, it is not narrow band at all.
Polarization from sky wave signals (dx) never are pure V or H, but they sure are not CP. Hence the sense of rotation the antenna is constructed for is not important. There should be some advantage over a V or H linear polarised antenna and i can live with the loss i will have from pure H or V signals coming in via ground wave.
But if i want to receive AO-7, what polarization should i set the antenna to? Is it RHCP or LHCP - just connect the delay line correctly, no big deal. Do i need to switch polarization?
Spin modulation comes to mind. Found nothing meaningful (to me) in the ARRL satellite experimenters book, but honestly , i did not dig too deep.
Now calculating the dimensions for the same antenna, but for 15m - 17m.