On 11 and 18 GHz PTP 820 S and C, there are two different hardware designs with same T/R and frequency range. The difference between them is that one HW platform supports only up to 60MHz, and the other supports a wider 80 MHz channel.
You can distinguish them from the SKU description details. Here is an example for 11 GHz:
Radios supports up to 60 MHz channel:
|C110082B029A||PTP 820C Radio 11GHz,TR500,Ch1W6,Hi,11185-11485MHz|
|C110082B030A||PTP 820C Radio 11GHz,TR500,Ch1W6,Lo,10695-10955MHz|
Radio supports up to 80 MHz channel:
|C110082B043A||PTP 820C Radio 11WGHz,TR500,Ch1W6,Hi,11185-11485MHz|
|C110082B044A||PTP 820C Radio 11WGHz,TR500,Ch1W6,Lo,10695-10955MHz|
Hope this helps.