To add, the larger the antenna diameter the more gain it has and the better the antenna is at rejecting interfering signals. Try and see what make of antenna you have and we can then check on what its spec is.
Yu can always go larger than what MC recommends. The original recommendation was 90 cm diameter, but was changed to 80-85cm at some stage presumably because this size antenna is more readily available.
Somewhere on the forum there is a MC post stating what the minimum gain of the antenna should be in dBi
Easyview, UEC 4T HD PVR, SD PVR, XV
Spare decoders: SD PVR(2), PACE HD PVR 4T, DSD 660, 1110, 1131, Explora 1
2 unmentionable FTA decoders
Win 10 Pro (64-bit) version 1703, build 15063.138
1.2m antenna, 8-way universal LNB, 2x6 MS, FSM permanently connected.
MS Edge 40 with MSEdge HTML 15