Agilent 8753ES and other VNAs alike

[Alexei.Polkhanov]

I found that there are quite a few VNA like Agilent 8753ES available on Ebay and private sales for attainable prices (6-7K). I assume it is early 90s. I believe that at least few people on this form had some experience working with these. Are these still good usable VNA? None come with any kind of calibration fixtures (another 1500 USD ?). What are most common non-obvious failures?
Thanks in advance.

[KJDS]

I've got a 6GHz 8753C here and it still works very well.

Make sure the test port connectors are not worn. Apart from that I've never seen one that didn't work.

To get an idea of performance, put a very good quality RF test cable between the ports without calibrating and see what the return and insertion loss looks like both ways round. Compare against spec for source and load match and coupler directivity.

[acbern]

I had a 8753c with a sudden failue in the osc (amp die died, thats probably where the word comes from ). Anyway, i looked arround in the net and it seems this is not an uncommon failure. So I would stay away from anything from a to c, the d and e/es should be ok. I bought a 3ghz version d with bridge installed (75ohms though, so I use it with min loss pads) and option 010 in good condition for about 1200 bucks recently, quite a good deal.

[rastro]

I recently purchased a 8753B which I had to fix a blurred CRT display.  Other than that the unit appears functional - I'm still in the learning process.
I believe "some" of the later units "D" & "E" version have built in facility for s-parameter.  Although my 8753B can be run with ad-hoc RF test configurations it has more utility and ease of use  with the addition of the S-Parameter test set.

S-Parameter Test Set:
The "B" unit I have uses a separate 85046A S-Parameter test set.  I picked up a 85046A S-Parameter test which included the 4 RF cables and control cable from a different source. 

Along with 85046A S-Parameter test set you will probably need 2 APC-7 to N adapters since port-1 & port-2 (DUT) on this unit are APC-7 type. 
Additionally "some" of the 85046A S-Parameter test set have different RF switch (Analog/Digital).  Some of the older 8753's   require a s/w or firmware upgrade to run with the digital RF switch.  I saw where someone had a hardware hack for the digital RF switch - basically a pulse stretcher on one of the control lines.

The calibration test set I'm still investigating.  There is a guy on eBay sell's an aftermarket set base price ~U$500.00 - he also seems active on yahoo HP & VNSA chat groups.  http://stores.ebay.com/Kirkby-Microwave-Limited?_trksid=p2047675.l2563.  I'm considering one of his calibration sets.

Regards
rastro

[G0HZU]

The HP8753ES is a wonderful VNA but they still fetch a lot of money and they can easily be damaged so my advice would be to be very careful.

At work I think we have about six of the 6GHz versions of the 8753ES. I think they date back to around 2002/3. I've nearly always got one of them on my workbench.

However, they are getting quite dated now and proving less and less popular at work because:

They only go to 6GHz
They are big and heavy
The LCD display is very gloomy and not as good as modern LCDs.
They have a floppy drive but no USB
They don't support the latest USB ECAL modules from Agilent.
They are not supported by Agilent anymore so this can cause issues with repairs/servicing
Other more modern models are much easier to use and are more portable with far better I/O

For these reasons I can only see the used prices tumbling over the next few years. Also note that there are several variants and the 8753ET is the basic TR version. The TR versions will plummet in value. There's also a full 3 port version which is quite neat. Some versions have an external s parameter test set and some have the s parameter test set built in. I prefer the version with the built in test set but there are good/bad points about either type.

A few niggles are listed below...

Be aware that some versions have APC7 connectors so you have to spend a lot of extra money on adaptors to N or SMA.

The LCD display is big but it isn't very inspiring to look at because of the limited pixel count and poor contrast ratio. It looks gloomy! The smith chart display looks quite crude and the smith chart marker text is hidden on the top line of the screen in tiny fonts and looks like an afterthought. There are lots of split/multi display options but some aspects of the UI are not intuitive.

If you make your own cal kit or buy an aftermarket one you will need to use the USER CAL KIT menu in the 8753ES. I can only assume that this part of the HP8753ES UI was written by a disgruntled/incompetent employee at Agilent because it is truly awful to navigate and there are 'wrong' ways to select menu options that appear to be 'valid'. I absolutely hate this aspect of the HP8753ES because I have numerous user cal kits here.

I've also noted some issues with tracking accuracy on big spans if you use the narrower RBW options on some of our 8753ES VNAs. The errors are only tiny but it can be annoying to see a tiny but fake 'step' in the response of an attenuator you are trying to characterise.

My advice would be only spend that amount of money if you need this VNA for business use. Otherwise try and buy an older C or D version for a bargain price from someone who doesn't know what they are selling. The C and D versions are still fabulous VNAs but they look VERY dated when switched off because of the CRT and the dated styling. So definitely more chance of getting one at a knockdown price

[Alexei.Polkhanov]

Thanks a lot for such a detailed reply!

[jyo]

I recently purchased a 8753B which I had to fix a blurred CRT display.  Other than that the unit appears functional - I'm still in the learning process.
...
Regards
rastro

I have bought a 8753B fw 2.01 for €1100 (~$1375): quite a good deal. But...
First the CRT failed after being on for an afternoon... I replaced the 1349A CRT by a Newscope-9: it's wonderful! (see http://www.simmconnlabs.com/2001/2115.html).
Next I tried to upgrade the firmware to V3 (found on http://www.ko4bb.com/manuals/index.php?dir=04_ROM_Images_and_Drivers/HP_8753/HP_-_8753B_v3_ROMs): it is incomplete 
What is the version of your firmware? If it's V3, I am interested by a copy of U4 U5 U24 & U25  (I have 1Mb EPROMS & programmer)
Thanks

[barnacle2k]

Be aware that some versions have APC7 connectors so you have to spend a lot of extra money on adaptors to N or SMA.

All Testset versions i encountered in the wild did have APC-7 connectors, but those adapters are not expensive. (75Ohms excluded)

 

I can only assume that this part of the HP8753ES UI was written by a disgruntled/incompetent employee at Agilent because it is truly awful to navigate and there are 'wrong' ways to select menu options that appear to be 'valid'.

I never had issues with the UI (but i very rarely use User cal kits).
There is worse, like old Rohde & Schwarz VNAs.

Which VNAs would you recommend as alternatives to the 8753?
The newer Agilent ones are rather pricy. 12k+ $
By the wy
What are your thoughts on the 8720?

[Bud]

You probably will not find anything better for the value than a 8753, so go for it, it is a wonderful machine (I have  a 6GHz 8753C ). As other said, watch for the display to be good and not dim, and get an S-parameter test set , either built-in or external. You still be using it when all toy Rigols will be already dead.

To me the display resolution is fine. An external GPIB adapter will allow to grab screenshots. If you are lucky you may get a VNA with the TDR option.

For a calibration standards set you can go for one from Dr.Kirkby (someone provided a link before), he knows what he is doing.

EDIT: For the theory and practical techniques part there is a book from the Agilent person who designed the 8753

Handbook of Microwave Component Measurements with Advanced VNA Techniques

As most engineering books it is expensive, but you can take my word you will not regret the purchase.

The other good book is from Rohde & Schwarz,  Fundamentals of Vector Network Analysis. I have both but R&S I read once and it sits on the shelf ever since. I keep Agilent's Dr.Dunsmore book handy. It has some typos that are easy to catch but the content is precious for a practical VNA-er.

[asteroidz]

I got my 6GHz 8753C from Ebay. Have not really used it though. The two-piece version has 20dBm output if you do not use the S-parameter testset, but then the function is limited to a Reflection/Transmission analyzer for up to 3GHz as far as the 8753C goes.
To mate with the APC-7 connectors, you can purchase a pair of APC-7 to N Male type cables to avoid expensive APC-7 to SMA adapters. N female to SMA adapters are commonly available and there are many brands of adapters to choose from. Huber Suhner Sucoflex or Micro-coax Utiflex cables are phase stable on my 6GHz VNA.
One limitation of the 8753 VNA is the calibration kit. You need to use Male and Female calibration standards for 2-port cal. Phase matched N to SMA adapters will be helpful to measure DUT with male only for female only connectors. I found that the Huber Suhner N to SMA adapters matched. The more expensive option is to buy a set of HP 85033 Cal kit with option 400, or to find some rare and equaly expensive Maury Microwave precision adapters.

[rastro]

Hello jyo;
Sorry for the slow reply - out of town for 3 weeks. 
I also have Firmware 2.01 Jun, 27 1988.  I was looking at doing the firmware upgrade but saw in a yahoo hp group that there was problems with the ver 3.0 firmware posting.  I have not pursued it much further.  If I recall correctly the problem was suspected with just one of the proms some of the bytes missing at the end???  If that is the case the missing bytes could be potentially guessed at based on ver 2.01 and/or X86 processor operations.  Probably would still require some solid reverse engineering skills - if at all possible.

Also just had to fix a SMPS problem with a 330uF cap causing cold start problems - back to normal now.

[Gandalf_Sr]

I was going to start a new thread on the 8753ES but a search found this one which, although it has had little activity for almost a year, is still highly relevant.

I am looking for a VNA to help me with 2.4 and 5.8 GHz antenna testing/design and  friend recommended the 8753ES and it seems there are a zillion of them on eBay right now.

In examining options I became confused by option 011 because it looks like that is a negative option, i.e. it takes the away the Built-In Test Set - I don't understand what that is and if it's the same as the S-parameter box that bolts underneath.  If I want to do antenna testing, what options should I look for?

Thanks in advance.

[acbern]

you need a test set, internal or external, internal usually is cheaper.

[Gandalf_Sr]

you need a test set, internal or external, internal usually is cheaper.

So, unless I see the test set as an external module under the VNA, then I should avoid option 011 - is that right?

[Bud]

I am not familiar with "E" model, I have  "C" one with an external S-par set and my vague memory tells me its 6GHz is only an option for the Receivers. For TX it is the external S-Set which has a  frequency doubler. So I'd say check the specs carefully if internal S-set covers the full range.

[TheSteve]

If you buy one with option 11(4 ports) you need to ensure you have the external S parameter unit - this makes the entire unit bigger. Unless it is really cheap as a package stick with the 2 port model that has the S parameter unit built in.

Shame the 8714 series was limited to 3 GHz max - N connectors standard, VGA and networking make it very appealing, and it is supposedly the "economy" analyzer.

[Gandalf_Sr]

Thanks everyone, there's a great Agilent document on NAs here, on page 36 they discus the difference between the T/R and S-parameter test sets.
Also the Reference Manual on the 8753ES with option 011 says this...

R, A, and B connectors. These connectors allow you to apply input signals when creating your own test setup. In addition, these connectors allow you to use the HP/Agilent 85046A/B, HP/Agilent 85044A/B test sets to simplify measurement setup - the difference between A/B is 50/75 Ohm respectively.

There is also the question raised earlier whether the internal test set goes past 3 GHz and on up to 6 GHz which, if it doesn't, might explain why there ever was an option 011.

[Gandalf_Sr]

So I looked up the 8753ES non-option 011 (2 port) version reference manual and, as best as I can tell, it does go all the way out to 6 GHz for the option 006 model.

And the detailed overall 8753 model specifications are here.

[bson]

R, A, and B connectors. These connectors allow you to apply input signals when creating your own test setup.

The canonical test setup is the sweep output is fed into a power splitter, and the outputs of the splitter is fed into the R (reference) VNA input and DUT input.  The output of the DUT is fed into A or B and you plot A/R or B/R as magnitude and phase (Bode plots), or polar.

[Gandalf_Sr]

R, A, and B connectors. These connectors allow you to apply input signals when creating your own test setup.

The canonical test setup is the sweep output is fed into a power splitter, and the outputs of the splitter is fed into the R (reference) VNA input and DUT input.  The output of the DUT is fed into A or B and you plot A/R or B/R as magnitude and phase (Bode plots), or polar.

Interesting, it seems like an option 011 version might be a viable unit to buy and they seem to be cheaper.  But does an option 011 version with the Out, R, A, and B connectors have any advantage in that you can set up your own test bench - do you think that was the point of Aglient offering option 011?

[acbern]

To measure S-parameter smith diagrams you need the S parameter test set.

[G0HZU]

So I looked up the 8753ES non-option 011 (2 port) version reference manual and, as best as I can tell, it does go all the way out to 6 GHz for the option 006 model.

And the detailed overall 8753 model specifications are here.

At work we have loads of the option 006 6GHz 8753ES VNAs and these are the full two port version (everything built in to the analyser) that comes with 2 APC7 connectors. They definitely do work all the way up to 6GHz

With a suitable full 2 port calibration using a cal kit you can use these to measure 2 port s parameters and measure/model components or circuits and export a 2 (or n) port model to a PC. However, the user interface is not great if you want to use a non standard calibration kit and you want to set the reference plane right at the component or feed point of a circuit.
You can still do it but it is quite fiddly and the user interface can be misleading in terms of which buttons you are meant to press for (correctly) setting up a user calibration kit.

[KJDS]

So I looked up the 8753ES non-option 011 (2 port) version reference manual and, as best as I can tell, it does go all the way out to 6 GHz for the option 006 model.

And the detailed overall 8753 model specifications are here.

At work we have loads of the option 006 6GHz 8753ES VNAs and these are the full two port version (everything built in to the analyser) that comes with 2 APC7 connectors. They definitely do work all the way up to 6GHz

With a suitable full 2 port calibration using a cal kit you can use these to measure 2 port s parameters and measure/model components or circuits and export a 2 (or n) port model to a PC. However, the user interface is not great if you want to use a non standard calibration kit and you want to set the reference plane right at the component or feed point of a circuit.
You can still do it but it is quite fiddly and the user interface can be misleading in terms of which buttons you are meant to press for (correctly) setting up a user calibration kit.

I remember giving a good technician the task of getting an 8753C to work with a 7-16 cal-kit. It took far far more effort than it should have done, probably a couple of days, when it really shouldn't have been more than an hours work if HP had done the job properly.

[G0HZU]

Yes, I tried googling for HP8753ES and user kit and you can see a few people discussing how poor the UI is in this respect.

http://www.keysight.com/owc_discussions/message.jspa?messageID=106284


This shouldn't be enough to put anyone off but my advice is to be prepared to have to do some headscratching and various trial/error tests to make sure the user cal kit data entry is correct.

A good workaround to all of this is to control the analyser via GPIB and write your own user interface in Windows or Linux that sets up things like port extensions or user cal kits. There is also the VNA Cal Kit Manager utility which was written by someone for Windows and then taken over by Agilent ( I think).

I've recently bought a slightly newer VNA from Agilent and I've had to spend quite a bit of time making sure I am setting up the user calibration correctly for my various cal kits. It's user interface is definitely better than the 8753ES in this respect but it was still a bit of a chore.

[KE5FX]

A few responses in vaguely-chronological order:

- Yes, the source modules can fail, and they aren't economically repairable in most cases.  You see a lot of reports of this happening, but you have to weigh them against the sheer number of 8753s out there.  These models were very popular.

- The cal kits sold by www.kirkbymicrowave.co.uk are a good match for the 8753s (including the 6 GHz variants.)  These are probably the ones rastro was referring to in post 3.  I'd recommend one of the Kirkby kits over any used kit found on eBay, unless you stumble across an unusual bargain.

- It's true that it is awkward to enter user calkit parameters by hand.  Fortunately, there's no need to do that.  Get a GPIB card  (the NI GPIB-USB-HS works well, always plenty of them on eBay) and use the VNA Cal Kit Manager.  If you get an NI card you can also use my homebrew app to save/load calibration states and .S2P files.  Because the 8753s' built-in nonvolatile storage is next to useless, these are both very useful resources.

- Both G0HZU and jyo are right, in that neither the 1349A green-phosphor displays in the -A/B analyzers nor the low-resolution LCDs in the -E and later models are especially great.  The color CRT used in the -C/D models was probably the sweet spot, but it's not as bright or sharp as it could have been.  jyo's approach of buying an older A or B model and upgrading it with one of the SimmConn LCDs is an excellent idea.  You can spend less this way and get a better display than any of the others.  The additional features and capabilities in the later models are not really that compelling for most users, so anyone shopping for an 8753 should give it some serious thought.

- For antenna testing with an 8753, the most economical route is an A or B model with a T/R test set.  Most people doing antenna work won't need a full S-parameter test set.   A T/R test set will allow the 8753 to display the magnitude and phase of the antenna's S11.

- It is not true that plotting S parameters on a Smith chart requires an S-parameter test set.  The test set contains literally nothing but a couple of T/R bridges or couplers and a relay to save you the trouble of swapping cables.  (Technically, the Smith chart wasn't even intended to support two-port measurements.)