Total posts : 45366
The p-p reading across the 50-ohm resistor appears to be too high by more than a factor of 2. I would do a very rough check of of the scope input amplifier and probe calibration by measuring a known DC voltage (maybe a DC power supply voltage checked with a DMM) with the same probe and scope input amp setting.
I see you say you checked the scope calibration. Please check again because the measurement is very suspicious. Let’s face it: If the true reading is 15 v p-p, your transmiter is really putting out more than a half watt–something that is not very likely.