Hello George,
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I got involved with nanoVNA's back in 2019. ?At that time I purchased one of the original units from China, now called a "classic" model. ?I subsequently sold it and bought others and sold those as well. ?I finally settled on the DeepVNA 101. ?I like it for a number of reasons including the metal case, the rotary encoder and the bright display that works well outdoors. ?It truly suits my needs quite well for most of my projects and experiments.
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My career in electronics was all in audio and video. ?Now that I'm retired, I started to teach myself about the other end of the spectrum. ?I got my amateur radio Extra class license back in 2007. ?I use my DeepVNA to learn about antennas and feed lines and filters and "spectral purity" issues. ?It's all great fun and I enjoy it a lot. ?And, like you, over the years I also have acquired a very nice collection of HP test gear. ?I even worked for the for a short while. ?But that's another story.
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Some of the things that intrigued me about the nanoVNA were the reports (on this platform) from people who were paid, full time "RF Designers" and "RF Engineers". ?They made statements like, "I use an $nnnK VNA in my lab all day long. ?I bought a nanoVNA just to see how it would compare. ?I was pleasantly surprised by how well it worked and how accurate it was (in its intended frequency range) and at such a low price-point." ?Ultimately, this got me thinking that I too should purchase a "real" VNA (used of course) and do my own comparisons. ?So I started watching eBay.
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A couple of years ago I eventually found a used Agilent 8753ES with an 85046A S-parameter Test Set that was in my price range. ?I did my due diligence and bought it. ?It's now 25 years old, but it's still an amazing piece of hardware. ?I acquired it during the pandemic lockdown and had lots of time to study it, learn it and become fully acquainted with it. ?That's not a trivial task. ?Then I made the time to compare it to my DeepVNA. ?I came out of this work very pleasantly surprised myself. ?Yes, the DeepVNA would only go to a Gigahertz, or maybe a Gig-and-a-half if I pushed it. ?Yes, the 8753 would go to 3 GHz. but I don't do that much work up there. ?All-in-all, I concluded that the DeepVNA was a very practical investment, and I do not regret, and most likely never will regret, spending the money for BOTH of the VNA's. ?They are BOTH incredible TEACHING and LEARNING tools.
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Having said all that, pay attention to those who said "watch out for the CRT". ?They are known to get so dim as to be difficult to read. ?My Agilent unit has an LCD display and will most likely out-live me. ?Yes, there are kits to replace the CRT with an LCD unit. ?But do you really want to invest money in upgrading an older unit?
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Are they hard to repair? Any weak points on these units?
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In doing my homework, before buying the used unit, I determined that they are beyond my capability to repair, in both skill level and daring, not to mention the gear I would need to measure it or get it re-calibrated. ?I would most likely have to take it to Colorado Springs to get it fixed and that wouldn't be cheap for several reasons. ?And IMHO, the "weakest point" is the YIG Oscillator. ?My understanding is, you don't fix them, you replace them. ?And that's not cheap either. ?Still, I'm very much enjoying mine. ?One more thing: as far as Calibration Kits, Cables and Adapters go, there are GOOD and BAD, LOW COST and EXPENSIVE parts out there. ?Just what level of accuracy do you really need. ?I bought CHEAP and they work and I'm slowly upgrading. ?I'm not unhappy, but then again, I'm not a NIST subcontractor either.
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Good luck with your decision.
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Sincerely,
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Larry?Goga, AE5CZ
Albuquerque, NM
