Well spotted! Usually all 90 Gregorians (Fibo, Philips, Delta Star.... maybe some others) come without support arms. In fact, I did not see any real picture of 90cm dish with support arms, only this drawing.
My Satellite Setup
Primesat/Famaval 1.8 PF C/ku/Ka, Octagon SX8HD1, SX88, Openbox S3 Mini HD-V8S Freesat V7 HD-V8 Finder, Amiko A4K Combo, Satlook Colour HD Spectrum, Sansui A909 Amp and BOSE Acoustimass speakers for the audio.
120cm dish has subreflector with 2 ears and it is slightly bigger (about 5mm wider and 5mm taller) than subreflector used on 90cm dishes. However, some 90cm dishes were equipped with subreflector with ears. We only can say that sub#1 is slightly bigger than sub#2 and it has ears for additional support arms. We also can weight them and observe some difference. Color also could be different. But, unfortunately, we can not say exact parameters of those sub-reflectors, there are several very important ones, but very hard to measure them, not even calculate.
Folks! What has just happened!!! One chap in Latvia bought second-hand FIBO dish. I think it is very vintage as 90cm dish has support arms. TBH I did not see such a dishes before! He got it for 25 EUR. No feedhorn, but, anyway. Very nice catch.
RimaNTSS, thank you for your welcome. At the beginning, i need understand myself some basis of physics for missed part (feedhorn) to renovate, and then try to build. Now things are new and interesting for me, will see how and when project are finished. I hope Fibo will return with new self-made feedhorn.
There is picture of Fibo feedhorn @RS900 fabricated View attachment 84382 , and as far as I know he is doing well in attaching non-fibo motor to polar-mount View attachment 84383 . I wish him good luck in this complicated endeavor.
Now a 95% of mechanical part for Fibo polar mount are complete. Here some pictures, how it looks, possition/angle sensor 13 bit absolute encoder and two end switches. Idea was to fix encoder code to controller for polar mount end positions, calculate midpoint - south after that make some movement to nearest satellite in my case 23.5E for dish adjustments. In this case polar mount mid will be adjusted strongly on S, in theory and all others should come automatically. Next step, controller programming and tests. There are some photo fixes for today:
My Satellite Setup
1.8 m CM at SMR 1224 + Elev. with 7 lnb changer Ku (lin - circ) - Ka (lin - circ) C (lin - circ)