The HP431C is an analog power meter with full scale ranges from 10uW to 10mW. (-20dBm to +10dBm) I have two of the HP431C power meters for sale at $50 each. But I have only one HP478A thermister mount, rated for 10MHz - 10GHz. I am asking $100 for the thermister mount. Jay Wicklund, KI7RH