In Nov 2019 the USA FCC chairman announced a proposal to sell 280 MHz of satellite frequencies (3.7-3.98 MHz) to 5G operators. The frequency sale auction is proposed starting late 2020.

This means that the only C band satellite range left clear is  4.0 to 4.2 GHz.

If the above comes to pass then a 5G base station transmitting in 3.7-3.98 MHz near a C band receive dish will cause severe interference into a broadband 3.625-4.2 GHz satellite receiver LNB.

You may already be using a pass band filter 3.7-4.2 to reduce WiMAX interference.  All tx/rx VSATs need a 6 GHz stop band transmit reject filters in front of the LNB to prevent damage to your LNB from your own transmit signals.

If you become affected by this interference problem then to stop this 3.7-3.98 MHz interference getting into your C band LNB you will need a new filter, but this will also stop you receiving C band signals below 4 GHz!

Advantech have developed pass band filters 4 - 4.2 GHz and 4.02 - 4 GHz. These are rectangular waveguide devices suitable to insert in front of the LNB. Flange: UDR40 CPR-229 FLAT.  Flange: PDR40 CPR-229 GROOVED.

The spec and pictures are here:
https://advantechwireless.com/wp-content/uploads/2019/12/PB-AWT-IRF-C-001-19339.pdf

What is not clear is if the filter also acts as a 6GHz stop band filter for transmit reject purpose, so ask about this.

I hope this attempt by 5G to grab satellite frequencies only applies to the USA.

Best regards, Eric