I have one of each but I'd like to have S-parameter capability which I need to learn and use for 440MHz and lower frequencies most likely at this time. At 82 I'm trying to find good options to minimize expense and weight. I don't have an HP 8503A test set and unless I find a good deal on one with APC-7 adapters with SMA or N connectors the 8505A becomes a shelf queen or back breaker until a viable option shows up. I see HP 8712B and HP 8753D with N connectors at reasonable prices. Also might consider a nanoVNA but there are so many I don't have clue how to select the best for low frequency use and that has a big screen, low price irrelevant if it's good quality and reliable. Any suggestions appreciated.
Thanks
Hank