Author Topic: Used Spectrum Analyzers for under $1k  (Read 57196 times)

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Offline Electro Fan

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Used Spectrum Analyzers for under $1k
« on: February 05, 2015, 03:39:49 am »
Here is an example of an eBay spectrum analyzer for under $1k.

http://www.ebay.com/itm/Tektronix-496P-Programmable-Spectrum-Analyzer-1-8GHz-/361202642579?pt=LH_DefaultDomain_0&hash=item54195aee93

There are the Tektronix 490 and 2700 series, and the HP 8500 and 3500 series, and probably others.  The only spec I have nailed down so far is more bandwidth (from as low as possible to as high as possible) is good :).  Realistically up to 1.8 GHz will do and whatever the low end can be within the budget will suffice.

Anyone have any recommendations on the best value model for a used spectrum analyzer assuming the unit is in good operating condition?  Anything you've found to be a favorite?  How feasible is it to get a decent used spectrum analyzer along with a tracking generator for under $1k?
« Last Edit: February 05, 2015, 03:41:59 am by Electro Fan »
 

Offline Wuerstchenhund

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Re: Used Spectrum Analyzers for under $1k
« Reply #1 on: February 05, 2015, 12:37:42 pm »
Here is an example of an eBay spectrum analyzer for under $1k.

http://www.ebay.com/itm/Tektronix-496P-Programmable-Spectrum-Analyzer-1-8GHz-/361202642579?pt=LH_DefaultDomain_0&hash=item54195aee93

There are the Tektronix 490 and 2700 series, and the HP 8500 and 3500 series, and probably others.

These were very good SAs in their days but now they are pretty much antiques which usually require a lot of care and which come with lots of unobtainium parts.

Unless you really need the bandwidth on a shoestring budget I wouldn't invest in such an dinosaur.

Quote
The only spec I have nailed down so far is more bandwidth (from as low as possible to as high as possible) is good :).  Realistically up to 1.8 GHz will do and whatever the low end can be within the budget will suffice.

Anyone have any recommendations on the best value model for a used spectrum analyzer assuming the unit is in good operating condition?  Anything you've found to be a favorite?  How feasible is it to get a decent used spectrum analyzer along with a tracking generator for under $1k?

Well, you said tracking generator so you want an old-style swept SA which are still somewhat expensive. However, if you can do without a tracking generator then there are quite a few options in the form of Vector SAs (VSA).

For example, have a loot at the Agilent E7495A/B. These are portable Base Station Test Sets which means you not only get a SA (500kHz to 2.7GHz, span from zero to full bandwidth) but also an RF generator (200MHz to 2.7GHz), a power meter, and (which is why many people want a tracking gen in the first place) a cable tester and TDR fault locator. It also has a GPS clock source. All in a sturdy ruggedized box that can take two rechargeable batteries and doesn't take much space on the bench (size-wise like a modern mid-range scope). They are a great bargain if you can find one with the right options below $1k (which with some patience is possible).

If I find the time I'll do a review of my E7495B over the weekend.

There are other alternatives, i.e. Anritsu MT8802A and Rohde & Schwarz CMU200. I have the latter, and it's a great device (mine has two RF gens, the audio analyzer, and the Reference OXCO).

There's also the Agilent E4406A which is a vector SA which goes to 4GHz but it only offers 10MHz span which is pretty poor. And it's essentially a SA only so it doesn't have any RF generator or other functionality.
« Last Edit: February 06, 2015, 08:30:42 am by Wuerstchenhund »
 

Offline MadTux

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Re: Used Spectrum Analyzers for under $1k
« Reply #2 on: February 05, 2015, 03:41:51 pm »
There's also the Agilent E4406A which is a vector SA which goes to 4GHz but it only offers 10MHz span which is pretty poor. And it's essentially a SA only so it doesn't have any RF generator or other functionality.

Seems to be normal for a vector SA, since for VSAs it probably goes like that: Input*LO => IF => some filtering => ADC => FFT. So 20MS/s sample rate ADC to get 10MHz span. Any higher sample rate, and the dynamic range goes down and price goes up significantly.

If you have the space, then buy a 8566/8568. Best SA for the price (less than 500$ w/o shipping if you can wait and pick it locally). The Tek 7L14 I had before my HP 8568B were crap (everything cramped inside that 3 plugin wide box, therefore everything is very small, difficult to disassemble and probe, no nice CF readout, drifty YIG, because not phase locked in higher span ranges). Since the 494P is related to the 7L14, I personally wouldn't buy it.
 

Offline avvidclif

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Re: Used Spectrum Analyzers for under $1k
« Reply #3 on: February 05, 2015, 04:13:05 pm »
I would look for either the HP 8560E series or the 8590E series. I have several pieces of HP gear going back to the early 80's that is run daily and has never been repaired or needed it. They're like the Timex of test equipment. I have only used Tek gear for oscilloscopes.

The engineers I have been associated with said "Tek make's scopes, HP makes everything else". It has served me well.

I had to look up the E7495 and from what little I could find the specs are only guaranteed from 375 MHz to 2.7 GHz. For what I do it would be almost worthless as most of my work is in the HF, VHF, & UHF range. It doesn't show a calibrated signal generator nor audio generators. It seems to me to be a very highly specialized cell test gear. I will be looking forward to your testing.
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Offline PaulAm

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Re: Used Spectrum Analyzers for under $1k
« Reply #4 on: February 05, 2015, 04:29:59 pm »
One of the problems with the 8566/8568 is an aging CRT.  These are getting a bit long in the tooth now and the CRTs get dim and unreadable at EOL.   It is possible to rejuv the CRT and get some additional usable life. There are available LCD retrofits, however, that give new life to them and even add color.

Cons: big and heavy, CRTs are getting old
Pros: Complete service doc available, good specs, common faults repairable, LCD replacement available.

It is possible to find a display and an rf section and upgrade the display for somewhere around $1K.

If you do go for one of these, try to get a set with the interconnect cables included.  They are often separated and the cables go for around $200/set when you can find them.  It's possible to make up your own, but the connectors alone for the BNC cable run around $80, unless you find a deal on surplus parts.  The bus interconnect cable is not a 1:1, but the pinout info is available in the service docs.  It's a 50 conductor cable, though so it's a real pita to make up.
 

Offline Wuerstchenhund

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Re: Used Spectrum Analyzers for under $1k
« Reply #5 on: February 05, 2015, 04:39:00 pm »
There's also the Agilent E4406A which is a vector SA which goes to 4GHz but it only offers 10MHz span which is pretty poor. And it's essentially a SA only so it doesn't have any RF generator or other functionality.

Seems to be normal for a vector SA

It's not. Both the E7495A/B as well as the CMU200 are also Vector SAs but both offer a frequency span from zero to the full bandwidth, and still offer reasonable high refresh rates. As do most newer VSAs.

The reason the E4406A only supports 10MHz span is because it's awfully slow processing. I guess Agilent thought it's ok for the intended purpose (looking at GSM and CDMA signals) but then other comms testers don't suffer from this problem.
« Last Edit: February 05, 2015, 05:04:47 pm by Wuerstchenhund »
 

Offline G0HZU

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Re: Used Spectrum Analyzers for under $1k
« Reply #6 on: February 05, 2015, 04:59:51 pm »
'
Quote
If you have the space, then buy a 8566/8568. Best SA for the price (less than 500$ w/o shipping if you can wait and pick it locally).

Agreed, these are still the best SA for the price if you just want an old school analyser with high RF performance. I have one of each here but there are plenty of downsides IMO. They are very big and heavy and there is a lot of fan noise. As PaulAm says, the CRT ageing is also a significant problem.  Also, overall reliability is becoming a serious issue with these old flagship analysers from HP.

I wouldn't consider buying any traditional spectrum analyser from Tek unless it was cheap and I was only needing mediocre performance.

I have always avoided the HP859x series of analysers and so has the company I work for. We have plenty of HP8560E thru 8563E and these are nice analysers although they are becoming very dated. However, They still cost well over £1500 (used) here in the UK even for a basic 8560E. So maybe these analysers are not in the running here because they typically cost a lot more than $1000.

« Last Edit: February 05, 2015, 05:13:35 pm by G0HZU »
 

Offline G0HZU

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Re: Used Spectrum Analyzers for under $1k
« Reply #7 on: February 05, 2015, 05:05:55 pm »
I have an old Advantest TR4172 here as well from the 1980s. It is an 1800MHz spectrum analyser with a tracking generator and it also has a factory option to allow impedance measurements with an external bridge from Wiltron. So it can be used as a basic VNA as well. I bought the first one about 10-12yrs ago for £400 and bought a 'spares' one for £250 about a year ago which is fully functional. It is a very good analyser but it is even bigger and heavier than the HP8568B. So it needs a very sturdy bench or trolley!

It was a serious contender against the legendary HP8568B in its day with quite similar performance  :)
« Last Edit: February 05, 2015, 05:15:34 pm by G0HZU »
 

Offline PaulAm

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Re: Used Spectrum Analyzers for under $1k
« Reply #8 on: February 05, 2015, 05:19:16 pm »
Another con with the 8566/68 is if you need a tracking generator, you have to find an 8444a with option 059.  These seem to have a minimum price of around $300-400 and it's another piece of gear to stack up
 

Offline Wuerstchenhund

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Re: Used Spectrum Analyzers for under $1k
« Reply #9 on: February 05, 2015, 05:27:55 pm »
I had to look up the E7495 and from what little I could find the specs are only guaranteed from 375 MHz to 2.7 GHz. For what I do it would be almost worthless as most of my work is in the HF, VHF, & UHF range. It doesn't show a calibrated signal generator nor audio generators. It seems to me to be a very highly specialized cell test gear. I will be looking forward to your testing.

I already mentioned the frequency range, and I suggested the E7495 only because the OP was asking for something up to 1.8GHz.

A bandwidth of up to 2.7GHz (E7495B, A variant is 2.5GHz) is also more than enough for lots of tasks as it covers a lot more than just cell phones (WiFi b/g/n, Bluetooth and other ISM stuff, ZigBee, DASH-7 and so on).

As to the E7495, the RF gen is certainly calibrated, and stability is pretty much excellent thanks to the built-in GPS reference. It doesn't have audio (but then the OP didn't ask for it!) but so don't standalone SAs. What it has is a Power Meter (requires an external measurement head, most Agilent standard types should do) which can be pretty handy. And unlike many other Comms Testers (i.e. Agilent 8960 Series 10) the E7495 is not "highly specialized", in fact unless you start one of the cell phone specific applications it looks and handles like any normal VSA, RF gen and Power Meter. The cable tester is useful as well, not only for profiling loss over the covered bandwidth but also for localizing defects (it can do 1-port and 2-port measurements). It can also measure Return Loss of cables, antennas and other RF parts. It runs Linux, and comes with USB, a PCMCIA and a CF slot, as well as a LAN interface, and Agilent offers some free program to control it remotely. The case is ruggedized for adverse environments and can certainly take some abuse.

The R&S CMU200 I also have is a bench/rack device, not a portable one like the E7495B. Mine does have audio (generator for up to 20 tones simultaneously plus THD and noise analyzer), the Reference OXCO option, two calibrated RF gens which also support various modulation types, a vector SA (10Mhz to 2.7GHz), a Power Meter (built-in), and aside from standard measurements can do a lot of other stuff. It also can be upgraded with various hardware options (i.e. I-Q analysis, Bluetooth analyzer).

Considering that the E7495B is from around 2010 I think it's a very good alternative to buying an old boat anchor like a HP 8568 which most certainly has long passed the zenith of its lifetime, and then invest even more money to keep it functioning. Don't get me wrong, these SAs were great in their days, but they are cheap because they are fragile and suck lots of power. This aside, even basic things like taking a screenshot is a pain in the arse with these old SAs. If you need the bandwidth (over 3GHz there aren't much alternatives if your budget is low) then it may be worth it, but certainly not if the requirement is 1.8Ghz of bandwidth.
« Last Edit: February 06, 2015, 08:34:53 am by Wuerstchenhund »
 

Offline nfmax

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Re: Used Spectrum Analyzers for under $1k
« Reply #10 on: February 05, 2015, 05:34:41 pm »
Since the E7495 asking prices seems to be around $2.5k, how relevant is this to the OP's question?
 

Offline Rupunzell

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Re: Used Spectrum Analyzers for under $1k
« Reply #11 on: February 05, 2015, 05:55:36 pm »
IMO, if one really needed a proper SA, get a hp 8566/8568, deal with the space requirements and get a unit in good condition even if the cost is higher. These SA's remain excellent in many ways. Find a way to deal with the space requirements as any good SA is complex and large. If a portable is really needed, choose hp again.

Used the Tek 492 series when they were new. They were OK, just OK. Performance wise the hp SA's were simply better. These were "portable" and were originally designed to meet a US military contract requirement for a portable SA. Don't like Tek SA's in general.

What matters in SA's is noise performance, display dynamic range (must be over 100 db to be useful IMO) stability and lack of spurious response in the display.

Not impressed by low cost made in Asia offerings.


Bernice


'
Quote
If you have the space, then buy a 8566/8568. Best SA for the price (less than 500$ w/o shipping if you can wait and pick it locally).

Agreed, these are still the best SA for the price if you just want an old school analyser with high RF performance. I have one of each here but there are plenty of downsides IMO. They are very big and heavy and there is a lot of fan noise. As PaulAm says, the CRT ageing is also a significant problem.  Also, overall reliability is becoming a serious issue with these old flagship analysers from HP.

I wouldn't consider buying any traditional spectrum analyser from Tek unless it was cheap and I was only needing mediocre performance.

I have always avoided the HP859x series of analysers and so has the company I work for. We have plenty of HP8560E thru 8563E and these are nice analysers although they are becoming very dated. However, They still cost well over £1500 (used) here in the UK even for a basic 8560E. So maybe these analysers are not in the running here because they typically cost a lot more than $1000.
 

Offline orin

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Re: Used Spectrum Analyzers for under $1k
« Reply #12 on: February 05, 2015, 06:03:26 pm »
Another con with the 8566/68 is if you need a tracking generator, you have to find an 8444a with option 059.  These seem to have a minimum price of around $300-400 and it's another piece of gear to stack up


You can make your own tracking generator for and 8568 with some microwave lego from Mini Circuits a 1025MHz signal source and a 2-4GHz isolator.

Parts required are a frequency doubler to get 2050MHz from the signal source, a mixer (at least 2-3.5 GHz RF and LO, IF down to DC), the isolator (eBay)  and some attenuators.  You get 70dB or so dynamic range.  Depending on your signal source, you may need a amplifier to drive the frequency doubler.  The isolator is used to isolate the SA's 1st LO output or noise feeds back from the mixer and raises the noise level on the SA.  I used the PA0KLT Kit E from sdr-kits for my signal source along with an amplifier to drive the frequency doubler.  The Mini-Circuits parts have SMA connectors, so you also need an assortment of SMA and BNC adapters/cables.

I looked up the mini Circuits part numbers that I used:

Mixer: ZX05-C42-S+
X2 Multiplier: ZX90-2-11-S+
Broadband AMP: ZX60-43-S+

However, looking at the prices of these parts, finding an 8444A option 59 might be the better option.  They can be found for less than $200 if you are patient.

It would be nice to sell the 8568 and get the Rigol DSA815, but the 8568 is so much better.

 

Offline orin

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Re: Used Spectrum Analyzers for under $1k
« Reply #13 on: February 05, 2015, 06:12:42 pm »
One of the problems with the 8566/8568 is an aging CRT.  These are getting a bit long in the tooth now and the CRTs get dim and unreadable at EOL.   It is possible to rejuv the CRT and get some additional usable life. There are available LCD retrofits, however, that give new life to them and even add color.

The LCD upgrade is/will be available here: www.simmconnlabs.com/2001/2094.html

I have a beta VGA version.  Xu, the creator of this kit has done an incredible job.  The display is way better than I'd expect for VGA resolution in its native mode.  There is a video on the site that shows the different modes.  It is also about one third of the price of the original LCD kits from other vendors!  Last I heard, these kits should be available this month.

Disclaimer: no relationship other than being a very happy tester of this upgrade.
 

Offline Rupunzell

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Re: Used Spectrum Analyzers for under $1k
« Reply #14 on: February 05, 2015, 06:20:46 pm »
Proving those Tek portable SA's did not stand the test of time.

Those hp Spectrum Analyzers work..


Bernice


I have a 496P.   Front end mixer was blown (replaced with Mini-Circuits part).  Phase lock was bad.    Bad caps....   After repairs, works alright for what it is.   Doubt you could get parts for it now.    Would not pay $1000 for one.    Make sure you can really check the thing out if you do go this route.   

Also have an old HP8569A.   Not good for low freq work.   Made a converter for mine.   Weighs a lot.   GPIB control is pretty limited compared with the 496P.   




     
 

Offline Wuerstchenhund

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Re: Used Spectrum Analyzers for under $1k
« Reply #15 on: February 05, 2015, 07:07:43 pm »
Since the E7495 asking prices seems to be around $2.5k, how relevant is this to the OP's question?

Who cares about the asking price? What matters is for what items are actually sold:
http://www.ebay.com/sch/i.html?_odkw=E7495B&LH_Complete=1&_from=R40&LH_Sold=1&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.A0.H0.XE7495&_nkw=E7495&_sacat=0

Only the ones which have the W-CDMA option fetch higher prices, but that option is irrelevant for using an E7495 as a standard SA/RF gen.

Finding one at a good price may require some patience but the same is true if you're shopping for an old boat anchor that doesn't already come as fixer-upper.
« Last Edit: February 05, 2015, 10:05:42 pm by Wuerstchenhund »
 

Offline dannyf

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Re: Used Spectrum Analyzers for under $1k
« Reply #16 on: February 05, 2015, 07:25:09 pm »
Get a $10 tv stick from ebay and load up a sdr package - you have a spectrum analyzer.
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Offline KJDS

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Re: Used Spectrum Analyzers for under $1k
« Reply #17 on: February 05, 2015, 08:06:59 pm »
The E4406A are good because there were so many dumped on the second hand market that they are cheap and readily available. Good close in performance for looking at modulation, it's a shame that the span is limited to 10MHz

I've also got a pile of HP8594E. They are ok, but I really should develop a tracking generator for them. The 856X is a better analyzer but they're typically twice the price.

Offline radiomog

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Re: Used Spectrum Analyzers for under $1k
« Reply #18 on: February 05, 2015, 08:36:09 pm »
Dang, I feel old.. more like a dinosaur, having a HP 141T  :-[
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Offline G0HZU

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Re: Used Spectrum Analyzers for under $1k
« Reply #19 on: February 05, 2015, 10:13:23 pm »
Quote
For example, have a loot at the Agilent E7495A/B. These are portable Base Station Test Sets which means you not only get a SA (500kHz to 2.7GHz, span from zero to full bandwidth) but also an RF generator (200MHz to 2.7GHz), a power meter, and (which is why many people want a tracking gen in the first place) a cable tester and TDR fault locator. It also has a GPS clock source. All in a sturdy ruggedized box that can take two rechargeable batteries and doesn't take much space on the bench (size-wise like a modern mid-range scope). They are a great bargain if you can find one with the right options below $1k (which with some patience is possible).

If I find the time I'll do a review of my E7495B over the weekend.

There are other alternatives, i.e. Anritsu MT8802A and Rohde & Schwarz CMU200. I have the latter, and it's a great device (mine has two RF gens, the audio analyzer, and the Reference OXCO).

The E7495B looks to be remarkable value if you can sometimes get them for around $1000. But I think you are being harsh against the HP8566/8 analysers.

These were fabulous analysers in their day and could be used for serious RF design work. I used both the 8568 and the TR4172 as design tools in the 1990s and the SFDR and close to carrier noise was superb on both of them. They are still very good even by today's standards.

Your two E7495B and CMU200 analysers would have been pretty much useless for the work I was doing back then if they had been sent back in time to me. It would be a bit like trying to dig up a concrete road with a plastic spoon because the close to carrier phase noise and SFDR are going to be pretty dire on both of them. So the analyser noise and SFDR would be far worse than the measurements I was trying to make.

But your E7495B analyser is portable and can do some modern tricks that the older analysers can't.

So when making a choice, a lot depends on what the analyser is going to be used for.
 

Offline Wuerstchenhund

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Re: Used Spectrum Analyzers for under $1k
« Reply #20 on: February 05, 2015, 10:21:21 pm »
The E4406A are good because there were so many dumped on the second hand market that they are cheap

Well, apparently not *that* cheap:
http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=agilent+e4406a&LH_Complete=1&LH_Sold=1&rt=nc

More or less around the same as an E7495. I guess it depends if the additional 1.5GHz/1.3Ghz bandwidth are worth the bandwidth limit and the absence of RF gen.

Also, the E7495 is still supported by Agilent, while the E4406A isn't.
 

Offline Wuerstchenhund

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Re: Used Spectrum Analyzers for under $1k
« Reply #21 on: February 05, 2015, 10:53:39 pm »
The E7495B looks to be remarkable value if you can sometimes get them for around $1000. But I think you are being harsh against the HP8566/8 analysers.

These were fabulous analysers in their day and could be used for serious RF design work. I used both the 8568 and the TR4172 as design tools in the 1990s and the SFDR and close to carrier noise was superb on both of them. They are still very good even by today's standards.

I know very well how good they were (heck, I spent over a decade writing test software for RF ATEs which usually involved a HP 8566A/B).

But all the great specs don't change a fact that these devices have long been obsolete and that any of those that are still in working condition will very likely fail sooner rather than later. The 8568A is from around 1978, that's 37 years ago! Old HP kit was durable but there's a limit to what can be achieved after that time. Aside from the increased failure probability, there's a lot of stuff that doesn't age well, and unlike modern devices these SA's do actually require adjustment to stay within their specs.

BTW, if I remember right the 8568A/B goes to 1.5GHz only anyways, so wouldn't even fit the OP's requirement (1.8GHz).

Quote
Your two E7495B and CMU200 analysers would have been pretty much useless for the work I was doing back then if they had been sent back in time to me. It would be a bit like trying to dig up a concrete road with a plastic spoon because the close to carrier phase noise and SFDR are going to be pretty dire on both of them. So the analyser noise and SFDR would be far worse than the measurements I was trying to make.

That's all very interesting but I believe we're trying here to suggest something that's right for the OP and not something that would have worked for you some 20 odd years ago, so frankly it's irrelevant if you could have made your measurements with the suggested kit modern back then or not. Back in the day I probably would have said take the HP kit but the OP lives in the here and now and clearly has different requirements, which seems to be a limited budget and 1.8Ghz required bandwidth, so he has to deal with the decision if he wants something modern (which means VSA) or an 25+ year old swept SA which due to the age alone comes with its own problems.

And quite frankly, if I compare the specs of the HP 8568A and the E7495B then the latter actually looks pretty good compared to the old kit:
http://www.dudleylab.com/hp8566-s.pdf
https://www.atecorp.com/ATECorp/media/pdfs/data-sheets/Agilent-E7495A_Specs.pdf

For example, frequency stability or displayed average noise level is better with the E7495. Much better.

The CMU200's specs also don't look too shabby:
http://cdn.rohde-schwarz.com/pws/dl_downloads/dl_common_library/dl_brochures_and_datasheets/pdf_1/CMU200_dat-sw_en.pdf
« Last Edit: February 05, 2015, 11:06:38 pm by Wuerstchenhund »
 

Offline orin

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Re: Used Spectrum Analyzers for under $1k
« Reply #22 on: February 05, 2015, 11:28:51 pm »

And quite frankly, if I compare the specs of the HP 8568A and the E7495B then the latter actually looks pretty good compared to the old kit:
http://www.dudleylab.com/hp8566-s.pdf
https://www.atecorp.com/ATECorp/media/pdfs/data-sheets/Agilent-E7495A_Specs.pdf

For example, frequency stability or displayed average noise level is better with the E7495. Much better.

The CMU200's specs also don't look too shabby:
http://cdn.rohde-schwarz.com/pws/dl_downloads/dl_common_library/dl_brochures_and_datasheets/pdf_1/CMU200_dat-sw_en.pdf


But look at the phase noise:

8568B is -100dBc at 3kHz, -107dBc at 30kHz.
E7495 is -85dBc at 30kHz; compare against the Rigol DSA815's -80dBc at 10kHz.
8566B is -90dBc at 10kHz but it's unfair to compare the '66B since that spec is for center frequency to 5.8GHz.

I look at these and stick with the 8568A.  If I want frequency accuracy, I can hook up the GPSDO to the 8568A and use its internal frequency counter.  FWIW, the 8568A/B will go over 1.7GHz with reduced accuracy and there is an option, H17 that makes the 1.7GHz limit official.
 

Offline G0HZU

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Re: Used Spectrum Analyzers for under $1k
« Reply #23 on: February 05, 2015, 11:32:15 pm »
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And quite frankly, if I compare the specs of the HP 8568A and the E7495B then the latter actually looks pretty good compared to the old kit:

It's risky and often misleading to look at shortform datasheets when assessing a spectrum analyser. Also, it depends which parts of the spec matter. If you want to check the close to carrier noise on a VHF synthesiser then the 37 year old HP8568 is still a very good analyser because it was designed for stuff like this. Your analysers are not.  eg the HP8568 typically manages a close to carrier noise performance of about -112dBc/Hz at a 300Hz offset at the lower part of its frequency range. This makes it an extremely powerful tool for synthesiser design, testing or faultfinding. I'd expect your analysers to be of limited use for this type of work.

Your analysers would also not be very good in terms of harmonic or IM distortion or general spurious performance.
To get reasonably accurate measurements of harmonic distortion the analyser's own internally generated harmonic distorion term needs to be about 15-20dB lower than the level of the harmonic to be measured. So stuff like this ideally needs a very strong analyser front end in order to keep measurement uncertainty within reasonable limits if trying to measure fairly low levels of harmonic distortion fairly accurately.

But your analyser(s) still might still be a better overall choice for the OP. It depends on what type of measurements and features (eg stuff like portability) matter most. I'm just offering my professional opinion based on many years' experience of using many of the classic high end spectrum analysers found in RF labs over the last 25 years or so right up to using the latest offerings from Agilent/KS.

Some of these 'classic favourite' analysers are available for very little money today (which is what this thread is about). I paid £125 for my HP8568B about 6-8 years ago.

I paid £400 for my Advantest TR4172 over 10 yrs ago and recently bought another for £250 as a backup or for a cheap source of spares.
« Last Edit: February 06, 2015, 12:09:49 am by G0HZU »
 

Offline Wuerstchenhund

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Re: Used Spectrum Analyzers for under $1k
« Reply #24 on: February 06, 2015, 06:44:58 am »
But look at the phase noise:

8568B is -100dBc at 3kHz, -107dBc at 30kHz.
E7495 is -85dBc at 30kHz; compare against the Rigol DSA815's -80dBc at 10kHz.
8566B is -90dBc at 10kHz but it's unfair to compare the '66B since that spec is for center frequency to 5.8GHz.

Yes, the phase noise is better on the 856xB. How critical this is depends on what you want to do, though. And the better phase noise is simply worthless if the bandwidth is too low for the OP's requirements.

Also, don't forget that the HP 85xx Series is mostly analog, and while these SAs had very good specs when they were new there's a good chance that after 30 odd years many of the units offered on ebay need at least serious re-alignments to reach their original specifications, or even component replacement. I certainly wouldn't blindly trust a 30yr old SA unless it has been recently calibrated, no matter who built it.

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If I want frequency accuracy, I can hook up the GPSDO to the 8568A and use its internal frequency counter.

Which means another box and investment for the OP who already said he's on a tight budget.

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FWIW, the 8568A/B will go over 1.7GHz with reduced accuracy and there is an option, H17 that makes the 1.7GHz limit official.

But 1.7GHz is still not the 1.8GHz the OP wants, and even if it were it's no good if the SA's bandwidth ends right at the upper frequency you want to look at.

It's risky and often misleading to look at shortform datasheets when assessing a spectrum analyser.

I am well aware that the specs aren't telling everything but what they do show is that the modern kit does noticeably better in certain aspects that the oldtimer. Other problems like scale fidelity also don't even exist on the modern kit.

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Your analysers would also not be very good in terms of harmonic or IM distortion or general spurious performance.

I'm not sure they would be that bad (the specs I found for the E7495 seem to be a bit sparse so I have no hard figures). In some areas they might not be as good as these old HP SAs but they seem to be still better than cheaper modern SAs like the Rigol DSA800, which are widely used despite performing worse in some areas than the mentioned HP 8568s. And at the moment we don't really know what the OP wants to do, all we know is that he's looking for an SA covering 1.8GHz and at below $1k, which isn't much information.

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But your analyser(s) still might still be a better overall choice for the OP. It depends on what type of measurements and features (eg stuff like portability) matter most.

Indeed. I think the OP should be a bit clearer in what he actually wants to do with the SA, as so far it's more a game of guess as to what properties would be the most important.

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I'm just offering my professional opinion based on many years' experience of using many of the classic high end spectrum analysers found in RF labs over the last 25 years or so right up to using the latest offerings from Agilent/KS.

Some of these 'classic favourite' analysers are available for very little money today (which is what this thread is about).

As I said, I know very well how good these old HPs were (as you, RF is part of my work for over 25 years, although mostly in higher bands so I'm more familiar with the 8566B than with the 8568 SAs). But I also do know very well how fragile these old SAs are (they already were back in the days!), and am under no illusion that for someone who wants something that "just works" on a shoestring budget these old dinosaurs can quickly turn into a huge money pit. If you're prepared for that and have the means to fix it then fine, but I didn't get the impression that the OP was able or willing to dive into a fixer-upper project.
« Last Edit: February 06, 2015, 10:50:10 am by Wuerstchenhund »
 


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