Hi,
note that I am a beginner with respect to electronics, and RF specifically. I would like to tune/characterize/inspect an antenna; for now, let's assume the antenna is supposed to work at around 1 GHz, but I'm interested in a general solution for all kinds of antenna sizes (well OK, let's stick to the ones that I would realistically get my hands on).
I would like to connect the antenna to a VNA (S11 measurements).
What I'm lacking is a good idea (ideally, calculation) how much (additional) input protection between the VNA and the antenna is needed.
What I know so far/have gathered:
- I have the specs of the VNA ready, so I know my "target"
- EM waves with frequencies "outside" the visible in the VNA hit the VNA's frontend nonetheless, so a surge at 800 MHz might fry my frontend even though I'd be looking at a very narrow band around 1 GHz
- static build-up in the antenna (several kV) and feed line capacitance (in the order of nF) can be problematic
- roughly calculating the power emitted when transmitting (I know enough that nothing is simple with electromagnetics )
What I am missing is an idea how much "external" power such antenna can pick up (that was not fed into the antenna by the VNA in the first place). I live in an urban environment, I do not know of any strong transmitters nearby, I do not have a microwave oven, and the (both physically and electrically small) antenna would be connected via the shortest path possible to the VNA in the inside (think unshielded apartment, no fancy lab).
I do not have a field-strength meter, and I'd rather not rely on one alone -- after all, a sudden surge that might be picked up by the field-strength meter would be picked up by the antenna as well, and fed into the VNA (if connected) before I'd be able to react.
My question: How could I determine the theoretical maximum an antenna can pick up, so that I can put appropriate attenuation between the antenna and the VNA?