[G0HZU_JMR]

Yes, I did mean the probe was meant for probing typical low Z circuits. eg for probing a signal path through a receiver or synthesiser or the low level stages of a transmitter.

I probably didn't explain it very well but if you could imagine a chain of 50R (UHF) circuits in a line, eg amplifier, attenuator, filter, attenuator, amplifier, attenuator, mixer etc the idea is the probe can be used along this circuit path without loading it too much. The idea is to leave the circuit all connected and just sniff along each stage. Because the probe looks like about 500R then it doesn't load the circuit very much. Obviously if you did this with a direct 50R cable to a 50R analyser the circuit would be double terminated at the probe point.

I've used this type of probe here at home and at work for many years and it can work well up to 2 or 3GHz if constructed carefully. For best performance it's best to include a coaxial DC block in the coax at the analyser end. This way you don't have to worry of the circuit has DC on it and a coaxial/SMA DC block will work much better (in terms of maintaining a flat response over the full bandwidth) than trying to add a blocking cap in series with the 470R resistor.