The above picture shows a REFLECTOMETER used to test and match waveguide and antenna's at 10,000MHz to 18,000MHz a very expensive tool a bargain at LONGLEAT Rally this year for just 25....And yes it needed DR RFL on it to repair the vernier control and the Pin injection at the top. After about 2 hours stripping cleaning and greasing the thing took off. The top "N" type sniffs a bit of the through RF at about -20db down on what is going through. By looking at the peaks and troughs you can work out the VSWR..(Voltage Standing Wave Ration)...if the level never changed as you move the cage along then you would have a perfect match. The unit is 50 ohms only. You can use as a sniffer a Spectrum Analyzer or a low level Power Meter.