I have read a lot of times in this forum that C-Band TV dishes are not suitable for operating 70cm. However:
Suppose that we have a 2,4m dish. By assuming a global efficiency of a 60%, our total gain would be around 18,5dBi
On the other hand, suppose that we want to achieve such gain with a common yagi antenna. Taking this calculator as an approximate reference, we would need a Yagi with more than 22 elements - which would be approximately 5 m long
In this case, I find worth going for a parabolic dish, since it can be shared between different bands (with different feeders) and is more mechanically consistent than a 5m long boom. Am I missing something? Why is then everyone so against dishes for UHF operation?
I know that the "optimal" way to obtain high gains at these frequencies would be using an antenna array. Nevertheless, a dish offers the possibility of working more than a single frequency band and takes up less space than a full 2x2 array.