I want to use the PNA in an outdoor "far field" antenna measurement system. I will have an HP 836xx external RF source on the GPIB (LAN), controlling its frequencies directly with SCPI, and use the PNA as my LO source (with an HP 85309). My LO will be tuned 20 MHz off my RF frequency. I have option 080 to allow this. My simple question is whether I set the 20 MHz as a frequency offset or if I just write a different frequency to the PNA than the RF source (taking into account the 20 MHz LO offset)? My guess is that I use a 20 MHz offset written to the PNA so that the source frequency is different from the receiver frequency (which is set to the RF freq.)? To simplify the question, if I set a 20 MHz frequency offset to PNA, and I set a 2500 MHz CW Frequency, is the receiver tuned to 2500 MHz and the source set to 2520 MHz? Thanks.