Here is a consolidated version of the Hidden Feature List for the Tecsun PL-880.
Thanks to Thomas over at The SWLing Post for publishing all of the hacks in one list.
|Function||Key||What to do||Radio State|
|Synchronous Detection||USB/NORM LSB/NORM||Hold button in until change occurs. One push to change back.||ON|
|Muting Threshold for AM/SSB, also sets FM Threshold on some versions||9||Select mode to adjust first (AM, SSB, FM). Press and hold, then adjust with either tuning knob. Press 9 again when done to save.||ON|
|DNR (Automatic adjustment of bandwidth, etc?)||6||Press and hold till display says 'ON' and again for 'OFF'.||ON|
|Display Firmware Version, and date||AM/BW||With radio OFF: press and hold until display turns on. Then press and hold again to get firmware. Press one more time for date||OFF|
|FM De-emphasis||5||Press and hold to toggle between 75 (USA) and 50 (Europe)||ON|
|Line-Out Level (only works on FM?)||7||Press and hold till current level begins flashing. Adjust with either tuning knob. Press again to save||ON|
|Adjusting Seconds on Clock||8||With radio off, press and hold, and then adjust seconds||OFF|
|Calibrating on AM (MW)||Snooze||Tune a strong MW station. Turn on SSB mode (USB/LSB). Move fine tuning till zero-beated and pitch matches non-SSB. Press and hold the snooze button till correction value appears in display, then press snooze again to save.||ON|
|USB/LSB Calibration||0||PRESS and HOLD the 0 button. Look at the UPPER RIGHT corner of the display. A 2-digits number is BLINKING as well as the Hz digits of the tuned frequency. RELEASE the 0 button, and adjust the FINE TUNING. Tune, de-tune and re-tune before calibration is perfect. Play a bit with it to understand how it works. Change is effective AFTER you press 0 again. Do for both USB and LSB modes. Check the tone when tuned to xxx.95 USB and xxx.05 LSB. They should sound exactly the same.||ON|
|Forcing External Antenna on MW/LW||Several||Visit http://goo.gl/AXSgMI for instructions and video||ON|