Want to purchase a spectrum analyzer - general questions, and something specific - Page 1
Forum section: electronics / testgear

author: toli
author_rank: Frequent Contributor
timestamp: January 11, 2015, 08:00:08 pm
content: Hi Guys,A brief story first. I'm dealing mostly with analog circuits, and every now and then some mixed signal things. This involves the things I do at home for fun (at the board level) and the things I do at work/school (only there I deal with IC's instead of board level). I'm thinking for some time now of starting playing with some RF projects at home, which gives me an excuse to invest in a basic spectrum analyzer.This is where you guys come in. My experience/understanding in the field is limited. I have played with some spectrum analyzers at the office/lab but never gave it much though. In our current lab we don't have one so I don't have access to one and that why I want to purchase one.I'd like to invest the minimum amount that is sufficient for my needs. Now for the real question, what are my needs? Well, I'm not sure yet, I see this as both an instrument that will help me with my projects, and a learning tool. The second part is actually more important for me. My past experience has thought me that when I have the tools at hand, I find things to do with these and this always helps me learn new things, and experiment with things I've learned back in my B.Sc/in books I've read.All the projects I can see myself working on will be in the few 10-100's of MHz range (maybe 500MHz as a top limit), so even if I leave some headroom for 3rd/5th harmonic, I think 1.5GHz is more than sufficient for my needs. I also think its good enough for educational purposes.If possible I'd like to get one with a tracking generator which would probably be a more versatile tool, especially for a learning tool.So I have a couple of questions:1 - Any general comments as to what I should be looking for in a first/basic SA, or any specific recommendations for this model on the other would be great.2 - One model a friend of mine mentioned is the Anritsu MT8802A (I must admit I'm unfamiliar with the name so I have no idea if they are any good). Browsing on eBay it seems somewhat cheap compared to other instruments with similar specs (BW/RBW), most of these include the spectrum analyzer module up to 3GHz. One of the units I've seen there last week was being sold locally so I could get it for ~1200$ and won't have to pay import tax (which is quite a bit over here).From the limited specs I foundI wasn't able to understand if the included signal generator can be used as a tracking generator for the spectrum analyzer or not. If there are any other thoughts on that model (pros&cons / other models that are a better fit) I'd be more than happy to hear.As my questions probably suggest, I'm quite a beginner with everything that's got to do with RF/SA's, so keep that in mind when postingAnd as always, thank you all in advance.

author: tautech
author_rank: Super Contributor
timestamp: January 11, 2015, 08:06:25 pm
content: You will get many votes for the Rigol DSA815-TG, plenty of threads on the forum about it.I don't know the model Anritsu you mentioned, however it is a well known respected brand.

author: toli
author_rank: Frequent Contributor
timestamp: January 11, 2015, 08:09:14 pm
content: 1. Thank you for the lightning fast reply2. The Rigol is something I've considered indeed. Only problem is getting it here, after international shipping + tax it'll probably end up costing well over 2K$. So If I could get something locally I'd really prefer to do it.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: January 11, 2015, 08:16:16 pm
content: Quote from: toli on January 11, 2015, 08:00:08 pmAnritsu stuff is good, but the MT8802A is not a Spectrum Analyzer, it's a wireless test set for cell phone applications. In short, it contains an RF generator, and some signal analyzer for stuff like GSM, AMPS and such. It can show the spectrum although it's a vector SA and not a sweeped SA (so there's no tracking generator, and things like RBW and frequency span are much more limited), and as you already found out the MT8802A only shows the bands used by the selected phone standard and not the whole supported bandwidth unless a certain option is installed. I remember that the whole unit was pretty slow and display and UI not great. It's also pretty old (IIRC from around 1996/1997).If you want such an all-in-one unit that can be used more flexible have a look at the R&S CMU200. Especially the models without W-CDMA and Bluetooth are often pretty cheap and should be obtainable for a similar amount as the old MT8802A.

author: Howardlong
author_rank: Super Contributor
timestamp: January 11, 2015, 08:21:09 pm
content: The MT8802A is OK, the spectrum analyser is an option though (ISTR option 7). It also includes an RF signal generator and a tuned RF power meter. It was originally meant for cellular testing, and this shows in the way the unit starts up and the menu system works. I use mine most days, and a couple of months ago I re-capped the entire unit because both the spectrum analyser snd RF power meter were almost unuseable with intermittent problems. A day and a half's work, but it's as good as new now. What's missing is a tracking generator and EMC style measurements for compliance testing on the spectrum analyser. However, an RF signal generator is more useful than the average tracking generator for RF in my book because trackng generators tend to have limited attenuation range. Finding reasonable documentation online hasn't been easy either, either for operation or for servicing.I also have a DSA815-TG for EMC pre-compliance testing. It's very good value for money for a new SA, definitely get the TG (tracking generator) version. The TG lets you test filter performance and, with a directional coupler and pad, one port scalar matching. However it does only go up to 1.5GHz.

author: toli
author_rank: Frequent Contributor
timestamp: January 11, 2015, 08:26:52 pm
content: Thank you both for the replies.Howardlong, thank you for clearing that for me. I wasn't sure if the generator could be used as a TG with the SA (although I've assumed it wasn't). The fact you had to do a complete re-cap makes worry about reliability tooAnyway, perhaps it would be best to look for something slightly more "user friendly" in this case.

author: Howardlong
author_rank: Super Contributor
timestamp: January 11, 2015, 09:04:58 pm
content: Quote from: Wuerstchenhund on January 11, 2015, 08:16:16 pmI don't believe that's entirely accurate. It will cover any arbitrary span from 10kHz to 3GHz at any frequency from 0Hz up to 3GHz. As you say it does not have a TG. RBW goes down to 300Hz, VBW to 3Hz. What's not great is its phase noise, but for many purposes it's fine. I don't agree with the UI, or indeed the SA being slow, it's as speedy as anything else around these days, although as you say, as it was developed for cell phone applications, the menus are geared around that to some degree.The RF signal generator covers any frequency from 300kHz to 3GHz, from -133dBm to -13dBm. The tuned RF power meter measures from -55dBm to +40dBm (actually it still measures well under -55dBm, typically mine measures down to -72dBm, but it displays "Level under" on the screen and the accuracy won't be as good at those levels).(Edit to add: what is slow is booting, it takes about 10 minutes!)

author: KJDS
author_rank: Super Contributor
timestamp: January 11, 2015, 11:16:22 pm
content: From memory, the MT8820A has limited spectrum analysis, I think about a 20MHz bandwidth at a time, whereas the MT8802 and MT8801 when they have the spectrum analysis options fitted are full spectrum analyzers. The signal generator and other analogue measurements on the MT8801 are also options, so it's important to buy one with the options you want if you're doing more than testing mobile phones.The other thing that is weak on the MT8801 is the display. It has a narrow viewing angle and if it's been left on turned up high for many years then they can go rather dim. Swapping colours about improves readability, but it's a frustrating task working out how to do it.

author: Mr Simpleton
author_rank: Unknown
timestamp: January 11, 2015, 11:22:40 pm
content: Quote from: KJDS on January 11, 2015, 11:16:22 pmNever seen nor used a MT8802, but the 8802A seems to cover 3GHz sweeps as shown in the top pic... unless you ARE talking about a 8820??

author: avvidclif
author_rank: Regular Contributor
timestamp: January 12, 2015, 12:48:55 am
content: Google is your friend. The 8802A is a communications service monitor geared toward the cell phone industry but it still didn't forget where it came from.Bottom line is it's a test bench in a box. Spectrum analyzer, signal generator, power meter (to 10w), audio oscillator, distortion analyzer. Various options add tracking generator etc. Lots of info on the web. Including usual problems and fixes also there. If the price were right and it's optioned right you have a lot to learn using it.I have 2 HP service monitors and still find new uses after 15 years, amazing boxes.

author: toli
author_rank: Frequent Contributor
timestamp: January 12, 2015, 06:08:49 am
content: Once again, thank you all for the replies.Howardlong, thank you for posting these pictures.avvidclif, google is a friend of mine indeed, we go back many years. However, I was unable to find any option of a tracking generator. Do you mean modifying the unit to have an output for a tracking generator?Assuming I could get one with the SA option, what would you say is the "right price"?

author: tautech
author_rank: Super Contributor
timestamp: January 12, 2015, 06:27:06 am
content: Quote from: toli on January 12, 2015, 06:08:49 amTest equipment options are normally provided in 2 ways.1. An additional PCB card to be purchased & installed2. All HW is in the equipment and supplied as such, the options are then "enabled" with code or from within a "secret"Service menu.

author: toli
author_rank: Frequent Contributor
timestamp: January 12, 2015, 06:28:17 am
content: That's what I see in most instruments, but I didn't find a reference to any TG in the datasheet of this unit

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: January 12, 2015, 06:39:24 am
content: Quote from: Howardlong on January 11, 2015, 09:04:58 pmI only played with a MT8802A once, and that was probably 16 years ago but I remember that it was slow, i.e. after pressing a key there was a noticeable delay before the unit reacted. It may well be that the particular unit had an earlier firmware (or some other issue).QuoteThese specs are pretty good. I was essentially in the same boat as the OP, I want some kind of simple SA for my small home lab, and possible and RF generator. I also looked at Anritsu MT8802A and MT8820A, but the first one was a bit too old for me and the second one is still pretty expensive. And both have a (in my opinion) a pretty ugly UI, and I couldn't easily find much documentation for both of them. Most of the other GSM testers (i.e. Will'Tek) were pretty basic (no SA, RF gen not freely useable). In the end I decided for a Rohde & Schwarz CMU200, and I also bought an Agilent E7495B Base Station Tester (which is a portable unit).The CMU200 is great bench-top unit. The RF gen covers 100kHz - 2.7GHz (0.1Hz steps, -130dBm to -27dBm up to 2.2GHz, -130dBm to -33dBm between 2.2Ghz and 2.7GHz), the power meter covers the same range in wideband mode and 10Mhz to 2.7GHz in selective mode, and measures depending on the input and type of signal from -80dBm to +53dBm (calibrated, not unleveled). The SA goes from 10Mhz to 2.7GHz, the span from zero to full (which many vector SAs in such testers can't do), RBW is from 10hz to 1MHz in 1/2/3/5 steps. My unit is the newer model with USB instead of PS2 ports for a keyboard and has the optional 2nd RF generator (same range as the first one) and the optional audio generator/analyzer (20Hz to 20KHz) which is nice. It's fast and has a clear and intuitive UI.Some of the units also come with the optional OXCO (3.5 x 10 to -8/yr) or the Reference OXCO (2 x 10 to -7/yr).If I find time I'll probably do some review of the CMU200.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: January 12, 2015, 09:44:02 am
content: Beware of old second user test equipment, especially service monitors (mobile radio test sets) and spectrum analysers. Many of these are 20+ years old, long since out of calibration and would cost a huge sum to repair and re-cal if they fail.A spectrum analyser is really handy if you are building and aligning scratch built radio kit. However, realistically how many people do that to the level that requires a spectrum analyser? Not many...For a bench analyser, the Rigol DSA-815TG is hard to beat for value and comes with a 3 year warranty. I have one and it's pretty good value and works well.For HF use an RF Space SDR receiver can double as a decent spectrum analyser, indeed there are a few SDR receivers of the "USB Dongle" variety that can be used up to 1 GHz or higher, I don't know how good their software is for spectrum analysis though, or how accurate they are at level measurement.Another option could be a hand held analyser such as the PSA series by Thurlby Thandar (http://www.tti-test.com). These are handy if you need to trace interference or check out noisy "wall wart" switch mode phone chargers. Their PSA 2 series has a quite wide min resolution bandwidth, but they work well and are slightly cheaper than a Rigol but of course lack a tracking generator.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: January 12, 2015, 12:17:54 pm
content: Quote from: Solder_Junkie on January 12, 2015, 09:44:02 amNot sure what's wrong with used test equipment. Not everything on the market is 20+ year old fragile kit that comes with 200 or so trimmers that need regular re-alignment. There is a lot of still very useful and even not that old kit out there, and a lot of that kit is pretty stable and reliable and stays within specs even after many years. So I'm not sure what you're on about.For example, my R&S CMU200 is from around 2004, and has last been calibrated (which for these devices is more a check if all parameters are within specs) in 2011. I don't have the Agilent E7495B I bought yet (still on its way to me), but this one is from around 2010. Both are devices using highly integrated components so there's little that needs re-calibration (and the few areas that do can be recalibrated by the user by a press of a button).For the CMU200 parts can often be found on ebay, as can be defective units which can be canibalized and used for upgrading (i.e. OXCO, 2nd RF gen), as this device is pretty widespread (R&S CMU200 and Agilent 8960 Series 10 are probably the most widespread wireless test sets, but the 8960 is still very expensive and less flexible than the CMU). Service Manuals are available, too.Especially Wireless Communication Test Sets can be great bargains. There are many younger units sold off cheap because they lack the W-CDMA/HSDPA or LTE options. Relative little money can buy you a very powerful test set that as individual components would cost much more, even used.And it certainly beats fiddling with USB analyzers and PC software.

author: HighVoltage
author_rank: Super Contributor
timestamp: January 12, 2015, 12:53:55 pm
content: I have seen several of the older Hewlett Packard Spectrum analyzers go for less than Euro 1000 on eBay lately.Something that was 7000 Euros a few years back with an upper limit of 12 GHz, is now around 1000 Euros and that is not a bad deal either. I started with such an older HP SA and then added the Rigol DSA 815T at a later time.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: January 12, 2015, 01:10:46 pm
content: Quote from: HighVoltage on January 12, 2015, 12:53:55 pmThese older SAs are usually the 85xx Series which are now approaching 30 years,. If they work they are great but these old analyzers need regular adjustment to stay within spec, and if something fails then this can easily be the end of it as there's a lot of unobtainium in these machines. The other thing is that they are very loud, huge, and use a lot of power.They can be a great bargain if you need 10, 15 or 20 GHz bandwidth and know how to fix them but for general use there are much better options these days.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: January 12, 2015, 01:12:32 pm
content: Quote from: Wuerstchenhund on January 12, 2015, 12:17:54 pmMuch of the surplus test gear is old and expensive to repair. I am trying to point out the significant risk of spending hard earned money on something that could end up being scrapped in a matter of weeks if it fails. Not many folks have the facilities to repair and re-cal something as complex as a HP analyser.

author: radiogeek97
author_rank: Regular Contributor
timestamp: January 12, 2015, 01:55:16 pm
content: I think one of the issues for me was that looking for a used SA on fleabay you MUST MUST do all your homework and know the minute differences in model numbers/options codes so you know what you are buying. I looked for 5 months on ebay and had some near purchases (outbid) but for the most part atleast lateley ANYTHING on ebay with a tracking gen (one of my must haves) was well over 1,500 usd and obviously that was with NO warranty. I ultimately chose the Rigol because of the price Warranty and features. The warranty being the kicker.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: January 12, 2015, 02:23:57 pm
content: Quote from: Solder_Junkie on January 12, 2015, 01:12:32 pmThat's all true and well, but as I am trying to point out this does not apply to newer gear like the discussed Anritsu MT8802A, or the R&S CMU200, or in fact the majority of wireless communication testers which can be used as SA (a functionality that due to the FFT calculations requires a certain set of processing backend which wasn't available in older testers).So far no-one has suggested that the OP buys some antique like a HP 8566B (in which case I'd agree with you, it's old and expensive to repair and difficult to maintain in working order so best to stay away from it unless you know what you're getting into). However, the mistake you make is to extrapolate the problems associated with such antique kit to newer devices as discussed in this thread.But of course, if you need full warranty just buy new.

author: Howardlong
author_rank: Super Contributor
timestamp: January 12, 2015, 03:21:07 pm
content: I have an 8565A, I bought it a few years ago for a K band project, and I couldn't justify a new 22GHz SA, and indeed I still can't! It still works, although it drifts a fair bit, as would be expected, and the storage display needs a bit of random button pushing to make it work. Can't say I'd recommend it unless you're prepared to be forgiving, and are fairly fit, it weights a LOT!Not an SA, but the Marconi 2955 comms test set still seems to command a reasonable price, useful as a signal generator and for transmitter and receiver testing up to a gig (the one I have takes up to 75W). It even has an integrated baseband oscilloscope. I've had one for about ten years, but I've had to fix it once, the line output driver transistor went south. A $1 fix, it took about ten minutes to find the fault from the symptomsThat probably about sums it up, if you buy old gear, you need to be prepeared to roll up your sleeves on occasion.

author: dan.soethe
author_rank: Contributor
timestamp: January 12, 2015, 07:38:28 pm
content: You can turn an ordinary oscilloscope into a spectrum analizer. Buy using a varacter diode based rf tuner and a sawtooth or triangle oscillator. Set the 'scope to xy mode then the output of tuner to y axis and the oscillator output to x axis and drive the varactor diode for tuning.... (this is just a technic, I don't have an exact circuit.)