Brian Dorey posted an article describing how he built his variable RF signal sampler:
It isn’t safe to connect the output of a radio directly into a frequency counter or oscilloscope due to the high voltages and currents on the transmitter and so we needed a way to sample part of the transmitted signal while dumping the output into a 50 ohm dummy load resistor.
After researching various options and commercial products we decided to build a variable RF signal sampler so we can use an attenuated signal from the radios main TX output.