Dear Members, I need your help to choose preamplifiers. The first question is why I need preamplifiers. It is common practice for EMI engineers to use preamplifiers during radiated emission measurement. I never thought of why until it was asked. I have to provide data to show the reason. I believe I have to consider the noise floor of a receiver or spectrum analyzer, antenna factor, cable loss, limits, etc. Can someone help me to do the math? The next question is what type of preamplifiers provides better measurement data? I did some search. It seems there are three types of preamplifers on the market: 1. Standalone preampliers, such as 8447D, 8449B. 2. Internal preamplifiers. 3. Preamplifiers mounted together with antennas. Here is a list of my questions: a. A receiver typically comes with a preamplifier covering frequency up to 3GHz. Does this mean I don't need to worry about a preamplifier to cover frequency range up to 3GHz? b. For a receiver or spectrum analyzer, there is an option for internal preamplifiers to cover frequency range up to the frequency range specified for the instrument. Is this a good choice compared to preamplifers mounted together with antennas? An antenna design expert educated me that it is better to have a preamplifier right after the antenna, then to a cable and test instrument. Do you agree with this? Thank you very much for your time and look forward to your help. Best regards, Grace Lin - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/
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