Aim of my experiment is to find out whether feedarms are not obstructing 105mm disc when phase center of the LNB is co-located with antenna's focal point.
By any chance, do you know how far from 105mm disc phase center is located? Something like 50mm?
For 2.4 GHz the phase centre is just above the patch so approximately in the same place if you follow the instructions. The 10 GHz is most critical, you can tolerate a large error at 2.4 GHz because the wavelength is four time greater. I would aim to make the distance adjustable in any case.
https://uhf-satcom.com/blog/patch_antenna there are pictures too. The typical distance from the reflector is 8mm as the phase centre is just above the patch. Your picture below has no patch and has far far too much waveguide coming out in front.
Make it as in the instructions, then make sure your feed holder allows you to adjust the the focus.
given your obvious mechanical skills, why not make a dual feed as exactly as drawn in the article ?
When you're done testing with it I'm sure a forum member would take it off your hands !
Good luck and have a great holiday.
But what I can be pretty sure is the hardware side of the issue, IMHO again, that original CM feedarms are no providing perfect solution, even if LNB-holder is changed. The best option is to change feedarms and LNB-holder, then you will have possibility to adjust the feed exactly in the focus of the antenna. Adjustable feedarms and LNB-holder give this possibility.
Hi to be honest there is no reason to make longer arms and no reason to over complicate a very simple modification, its as simple as this. All my reports here are with the above setup 1.2 channel master dish.
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Yes, it is quite simple and well camouflaged (little bit rusted holder though )but I do not think this solution can provide best performance of the system. Seems that LNB is located too close to the surface of the dish, so LNB's phase center could not be co-located with antenna's focal point. Reception is, of course, possible, but, again it will never be best as it could be.
P.S. looked in your link but did not find your name and any pictures of your dish. But, I am pretty sure, if you were placing LNB in proper position you would certainly have even more astonishing reception results whatever good/bad they are right now.