I install antennas in areas where I have verified that 600MHz LTE signals are now present. I've been using Linear LPF-600s (the only >600MHz filters I could find) and they seem to work fine. However, I went to order more, found they were out of stock all over and the one place I ordered from e-mailed me back and told me they were on backorder with Linear until November. I checked Tin Lee and their filters start at $150. Any other options?