Copper blocks should make redstone reach further.

Placing redstone powder on copper blocks would sustain/make the signal reach further. The more oxidized the copper blocks are the less the redstone signal is extended/sustained. E.g. The unoxidized Copper Block output signal-boost could be 4+ signal strength on the redstone above it, whereas a fully oxidized Copper Block output signal-boost would be 0+ signal strength. Copper grate blocks would not extend any redstone signal.