With hamfest season coming up those that are bringing a  PRC-77 might consider converting it to Noise Squelch instead of using the Tone Squelch.
      I've up dated my web page on the PRC-77 Noise Squelch and included the W3KKC board as well as my mod to the A54 board and the PEOSSB mod to the A54A (IC version).  Lots of other squelch info is still included. Incidentally my mod to convert the A54 board only requires two resistors, two 1N914 diodes and two small caps.  Takes about an an hour and a half.
K4CHE

         http://k4che.com/PRC77-Squelch/PRC77-Squelch.htm