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How do the features in old VNAs and SAs differ from new ones?

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joeqsmith:

--- Quote from: nctnico on March 09, 2024, 07:26:10 pm ---My biggest issue with older equipment is that lack of a USB or ethernet port to save data / screen captures. My experience with floppy to USB converters has not been good either. Nowadays I use a Prologix GPIB to ethernet interface to interface to old equipment which works well in combination with some Python scripting.

--- End quote ---

My biggest issue with older equipment is getting it fully functional and then maintaining it.  For higher end equipment, locating replacement parts that may have been custom can be costly and  time consuming.   My advice if you are buying used, consider making the calibration part of the agreement.  Maybe have them ship the unit to the manufacture and if it passes cal, you cover all the cal and shipping costs.   

My old PNA and scopes support Ethernet which is how I control them.   For older test equipment,  I use an Ethernet - GPIB controller from National Instruments.  For the USB floppy, I have one from eSYNiC.   For printing,  I designed a Centronics to Ethernet reverse print server (using a Motorola 6811).   

xrunner:
If I want a screenshot from the old hp 8594E I don't need no stinkin USB stick or floppy drive. I can brute force one ... using my phone camera.  :-DD

nctnico:
Where is comes to actual equipment recommendations:
Many base station analysers have spectrum analysis and network analysis features. I got one from JDSU / Viavi which does both. These typically don't break the bank. The JD745B/JD785B models could be interesting but make sure to understand the available options versus what is installed on the units.

G0HZU:
For many years, the industry standard spectrum analyser was the 22GHz HP 8566B or the very similar looking 1500MHz HP 8568B. These are still fabulous spectrum analysers today, but they are big, heavy and have a LOT of fan noise.

They are also going to be fairly unreliable today. The log detection is done in the analogue domain so the log accuracy isn't that great, especially over an 80-90dB range. The RBW filters are all analogue. So it is very slow to sweep on narrow spans and the filter accuracy is going to be a bit dodgy by now unless it has been serviced fairly recently.

They still easily outclass the modern Rigol and Siglent analysers in terms of spurious free dynamic range and phase noise but they lose out on pretty much everything else. The CRT displays are getting very tired now although the vector system they use is equivalent to a 1000 x 1000 display. So (in theory at least) this is better than the Rigol or Siglent. However, most people will much prefer the larger modern display of the Siglent, and I can see why. The Siglent analysers do have a great looking display. For most hobby users and some professionals, the Siglent SA is hard to beat.

Few professionals will still be using an HP 8566B or HP 8568B. There are too many modern alternatives with modern features that these older analysers don't have.

The other option is the HP 8560/8563 portable analyser. These have similar performance to the 8568 and 8566. At work these 8560/8563 portable analysers are dropping like flies. I think the company still had about 8 of them a couple of years ago and all of them have died in the last year or so. Nobody wants them, nobody wants to pay to have them repaired and they are all going (or have already gone) for WEEE recycling.

The HP 859x series are very popular but the RF performance is grim. It was grim 30 years ago and in my opinion these analysers aren't worth having unless you are desperate and don't care how grim they are. The same applies the Tek 49x series of spectrum analysers.


G0HZU:
In terms of VNAs, the old HP 8753x series offered really good performance. Easily better than the modern sub $2k Siglent VNAs and they also offer bias tees at the rear. The main niggle with them is the clunky and restrictive user interface. Newer VNAs from Agilent/Keysight that replaced the 8753x series are much more versatile when it comes to setting up the calibration of a test fixture for example and the newer VNAs support unknown thru calibration which can be very useful. They also support the popular Agilent Ecal modules. 

The popular VNAs from Siglent that are based on their budget spectrum analysers are going to be fairly grim in terms of performance. However, if you just want to do casual measurements of antennas or filters then they should be fine. The big old lab VNAs are still hard to beat if you want to make fairly precise measurements of n port networks up into the GHz region. No nanovna or budget Siglent VNA is going to come close in this respect.

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