Update: Mfj-259b Firmware

The bottom line: The is largely a myth born from wishful thinking and confusion with newer devices. The unit was built to a "set and forget" philosophy. Its longevity—many units from 1999 still work perfectly—proves that firmware updates are not necessary for reliable operation.

There is no "firmware update" in the modern sense for the MFJ-259B. You cannot download a file from the internet and upload it to the device using a cable. mfj-259b firmware update