I came across a weird case, I have a low power 440MHz repeater transmitter, which I thought to set at about 10 watts. I made this measurement using an accurate offset attenuator and service monitor.
Like usual, adding more lossy coax, more connectors, and greater lengths dropped the power as usual.
However, when I was trying to measure loss through one of the transmit cavities of a duplexer, I was surprised to see an increase in the output power, up to 10.9 watts!
I then connected directly to the little stub of coax which I was connecting between the cavity and measurement system, and the power went up to 12 watts.
Does this mean there is an impedance mismatch somewhere down the line? I understand I am not running the best coax (only LMR240), but I thought it would still all be 50Ω.