As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UNABLE TO TRANSMIT ON HF2. SELCAL WORKS, CAN HEAR ATC, BUT CANT TRANSMIT. TUNE TONE STAYS ON FOR A WHILE WHEN INITIALLY TUNING RADIO TO A FREQUENCY. GROUNDED - YES. VERIFIED HF#2 RADIO ONLY RECEIVES, DOESN'T TRANSMIT. REMOVED AND REPLACED HF2 ANTENNA COUPLER REF B737-800 AMM 23-11-61. OPS CHECKED HF2 REF AMM 23-11-61.