Good low-cost spectrum analyzer - Page 1
Forum section: electronics / testgear

author: Asgards
author_rank: Newbie
timestamp: July 07, 2013, 04:47:53 am
content: I have been looking for a spectrum analyzer for exploring 433Mhz and 915Mhz frequencies. All analyzers I can find online cost like $8000 or more! Isn't there really no small simple low-cost analyzers available??

author: Kappes Buur
author_rank: Regular Contributor
timestamp: July 07, 2013, 04:52:59 am
content: http://www.rigolna.com/products/spectrum-analyzers/dsa800/dsa815/Would that suffice?

author: warp_foo
author_rank: Unknown
timestamp: July 07, 2013, 05:23:59 am
content: I'd be happier if it covered audio frequencies.m

author: peter.mitchell
author_rank: Super Contributor
timestamp: July 07, 2013, 07:03:49 am
content: 9khz is pretty low, a lot of them only go down to 50k! you have to look for a specific audio freq one i'd guess if you want an audio freq one.

author: AndyC_772
author_rank: Super Contributor
timestamp: July 07, 2013, 07:14:02 am
content: http://www.ebay.co.uk/itm/Agilent-HP-8594E-Spectrum-Analyzer-9kHz-2-9GHz-Calibrated-Option-041-/181148455645?pt=LH_DefaultDomain_3&hash=item2a2d4a12dd

author: WarSim
author_rank: Frequent Contributor
timestamp: July 07, 2013, 07:28:10 am
content: Spectrum Analyzes are not intended to be used at audio frequencies.And if I did find one that did I would be concerned about it.I would have too many questions about their implementation.If you want an audio frequency spectrum analyzer you could use what i believe is the intended equipment, an audio distortion analyzer. I have used a few with graphical display akin to a spectrum analyzer.Another much cheeper and less capable option is a pseudo spectrum analyzer aka the FFT function on a oscilloscope. Given enough memory depth could go very low. To keep in the affordable realm you may need to use computer based FFT to go down to 4Hz. But there is a lot more memory in oscilloscopes theses day and may be capable of what you need now.Andy good find, for an E version. (If I remember my model to frequency span translations correctly)These do have noise floor issues if you are looking for -88dbm or less if you are not good at using one.Alas this one is not very useful in the audio band. I think you are still looking for a two instrument solution.

author: EEVblog
author_rank: Unknown
timestamp: July 07, 2013, 07:47:32 am
content: Quote from: warp_foo on July 07, 2013, 05:23:59 amThey are called Dynamic Signal Analysers.Spectrum analysers do not do audio frequencies.

author: kripton2035
author_rank: Super Contributor
timestamp: July 07, 2013, 07:59:39 am
content: there is also the RF Explorer, very nice for the priceof course it's not as featured as a real spectrum analyzer but may be it's enought for you ?http://www.seeedstudio.com/depot/rf-explorer-m-22.html?ref=side

author: WarSim
author_rank: Frequent Contributor
timestamp: July 07, 2013, 08:25:01 am
content: Hmmm I think I got the equipment name wrong.The dynamic signal analyzer i just googled looks exactly like what I have used and though was called something else.

author: rf-loop
author_rank: Super Contributor
timestamp: July 07, 2013, 09:01:47 am
content: Quote from: EEVblog on July 07, 2013, 07:47:32 amYes but not always.Hewlett-Packard. (what was destroyed by Agilent)Historical state of art modular spectrum analyzer. 141T and plug ins. From 20Hz to 18GHzAnd they also call these Spectrum Analyzers.Typically we talk audio freq start 20Hz.LF plug in:HP8556A is for 20Hz to 300kHz (Ranges 0-30kHz and 0-300kHz)Average Noise Level with 10Hz RBW without any "tricks"... -150dBm 600ohm and -142dBm using 50ohm )Also this plug in include tracking generator.Of course it is history, but fun, these machines do not die.. what is more amazing is that even today, with these old gears can do lot of nice work.Specially this plugin I have used (long long time ago) for some special tiny experimental work related to Under Water Acoustic (data) communication

author: PA4WD
author_rank: Newbie
timestamp: July 07, 2013, 10:11:03 am
content: rtl2832u chip based DVB-T USB Stick.Good for viewing signals, not so good for measering.But very cheap on ebay 15$ or less.

author: nctnico
author_rank: Super Contributor
timestamp: July 07, 2013, 10:43:36 am
content: Quote from: WarSim on July 07, 2013, 07:28:10 amActually there are spectrum analyser specially for audio applications.On topic: Atten has several low cost analog spectrum analysers. Then there is Rigol which has a low cost line. Another option is buying a second hand spectrum analyser but those are still expensive unless you buy a crappy boat anchor. A cheaper option might be an 1GHz oscilloscope with FFT.

author: Rerouter
author_rank: Super Contributor
timestamp: July 07, 2013, 11:32:18 am
content: not to de-rail it to much, but if fft is the half capable method, what are the other better and more capable ones?

author: G0HZU
author_rank: Super Contributor
timestamp: July 07, 2013, 11:52:03 am
content: QuoteQuoteAll of my RF spectrum analysers can be used at audio frequencies. eg one covers 100Hz to 22GHz another does 50Hz to 1800MHz and another one is similar.It depends partly on how much the analyser cost though. To be useful at audio frequencies the analyser needs to have a very clean and stable synthesiser and also needs to support a very low resolution bandwidth (ideally <=10Hz RBW). Eg the close to carrier phase noise on the first local oscillator (up at several GHz) ideally needs to have phase noise of -100 to -110dBc/Hz at, say, 500Hz offset from the carrier. This used to mean big money 20 to 30 years ago.However, these days I would favour using a decent PC soundcard +DSP for audio analysis because the refresh rate is so much faster than my old analysers.The little Rigol 815 looks to be a reasonable RF analyser as long as you don't expect to use it for spurious free measurements over a wide dynamic range and you can live with the high phase noise and 100Hz minimum RBW. i.e. it's not going to be that great on very narrow spans in terms of dynamic range because of the high phase noise and it only goes down to 100Hz RBW. It doesn't cover the audio range but you can use a PC soundcard for audio work anyway.

author: edpalmer42
author_rank: Super Contributor
timestamp: July 07, 2013, 02:01:08 pm
content: Quote from: EEVblog on July 07, 2013, 07:47:32 amWhat? I know of two HP spectrum analyzers that do audio. The 3585A (20 Hz to 40 MHz) and the 3580A (20 Hz to 50 KHz). I don't know anything about the 3585A except the specs. I used the 3580A many years ago.Ed

author: JackOfVA
author_rank: Unknown
timestamp: July 07, 2013, 02:38:39 pm
content: The HP8568A and B have a lower frequency limit of 100 Hz if I remember correctly, max frequency 1.5 GHz. I use mine down to 10 or 20 KHz every now and then, but mostly use an HP 3562A Dynamic Signal Analyzer for 0-100 KHz, as general purpose RF swept frequency spectrum analyzers have some drawbacks in the audio range, such as usually not having a log frequency sweep and also have 50 ohm input impedance which is a bit confining in dealing with audio hardware. The 3562A's 1 Mohm input impedance is much more useful.If all you need to do is look at the spectrum with a relatively narrow bandwidth, say 200 KHz maximum, then an inexpensive SDR receiver, such as the FunCubeDongle Pro is worth looking at. It's not a calibrated instrument but it certainly meets the minimum price point. Details athttp://www.funcubedongle.com/... I use mine with SDR-Radio softwarehttp://www.funcubedongle.com/

author: gregariz
author_rank: Frequent Contributor
timestamp: July 07, 2013, 02:44:05 pm
content: Quote from: rf-loop on July 07, 2013, 09:01:47 amCarly Fiorina's bum destroyed HP.

author: profmason
author_rank: Contributor
timestamp: July 07, 2013, 02:57:10 pm
content: Rigol dsa815 mentioned earlier is a great piece of kit. Game changing almost in that you have a real tool for $1300. Got one a year ago for evaluation and communications faculty loved it.

author: Asgards
author_rank: Newbie
timestamp: July 07, 2013, 06:31:22 pm
content: Thanks for the suggestions. The Rigol looks really good and the price is very reasonable, however it is actually more than what I need, so as somebody suggested earlier, I decided to go with the small handheld unit from Seed Studio, .. its only about $100!

author: kripton2035
author_rank: Super Contributor
timestamp: July 07, 2013, 07:42:27 pm
content: please be aware that if you want both 433 and 915MHz you need the ISM rf explorer model that is $175for $99 you have 433MHz OR 915MHz OR 868MHz but only one of them.

author: fpliuzzi
author_rank: Regular Contributor
timestamp: July 07, 2013, 09:59:00 pm
content: Asgards,If you decided to get the $129.00 RF Explorer model WSUB1G (240 - 960MHz BW), it certainly is a handy little device. Ariel has been doing a good job of adding new features to the firmware since I've owned mine.If needed in the future, the optional RFEM WSUB3G daughter board can be plugged into your RF Explorer to extend its bandwidth (15MHz - 2.7GHz). I found this upgrade very easy to do to my unit.Regards,Frank

author: WarSim
author_rank: Frequent Contributor
timestamp: July 07, 2013, 10:35:45 pm
content: Frankly I am kinda shocked they call something that doesn't go upto at lest 1GHz a Spectrum Analyser.

author: gardner
author_rank: Regular Contributor
timestamp: July 12, 2013, 03:49:26 am
content: I anticipate taking delivery of my 3G Combo RF Explorer within the next few days. I am still uncertain how good a tool it is, but it's the closest I can justify coming to a proper spectrum analyzer. The 3G combo model goes from 15MHz to 2,700MHz, which covers everything I (currently) care about. The projects I have in mind are messing with:433Mhz antenna designs for little SAW OOK radio projectsmessing with and debugging 2,400Mhz ISM Nordic radio modulesGSM 1,900 antennas and dish feeds500-700MHz terrestrial broadcast TV antennasAll non-critical, and, I hope, within the abilities of this little toy.

author: kripton2035
author_rank: Super Contributor
timestamp: July 12, 2013, 10:46:26 am
content: this little toy is very nice to measure rf levelsthen if you want to analyze the transmitted datas, you can "play" with this other toy:http://altelectronics.co.uk/shop/arduino/arduino-rf-433-92-mhz-shield/prod_78.htmland an arduino of course !

author: w2aew
author_rank: Super Contributor
timestamp: July 12, 2013, 02:28:43 pm
content: Quote from: EEVblog on July 07, 2013, 07:47:32 amMany of them do. I have one sitting next to me that covers from 1Hz to 26.5GHz...

author: kumar
author_rank: Contributor
timestamp: August 07, 2013, 06:07:16 am
content: Hi,I am new to EMI pre-compliance analysis and wish to purchase RF Explorer 3G COMBO. Can any of you please sort out a few queries?1) Why the dB scale starts at 0dB and goes down to negative value? The results from the compliance labs is a positive figure in dB ( for ex: 30dB radiation at 50 Mhz. It is never -30 dB ).2) Let us assume that the lowest dB level (in a spectrum analyzer ) is set at -100 dB ( Do you call this noise floor?)If the peak at 50 MHz is -60dB then how much the radiation is in positive value; is it 100-60=40 dB? Or something else? Does any one have a formula to calculate it?3) How good is RF Explorer 3G Combo? We just want to use it for solving the EMI problems.

author: rf-loop
author_rank: Super Contributor
timestamp: August 07, 2013, 06:43:10 am
content: Quote from: kumar on August 07, 2013, 06:07:16 amIt is not dB. it is dBm typically in spectrum analyzers. (or something other example dBu (dBuV)).Edit: Add note: dBu is NOT dBuV but dBm is dBmW.And more confusing I have seen (in history) even study text book where is used dBu for dBuV just using this logic.It need be careful with this (and always care need if talk with audio peoples). Also I have mis used these for dBuV specially in my paper notebooks becouse I'm lazy to draw V.Voltage V0 = 0.775 V ? 0 dBuAudio engineering,no impedance reference!No impedance reference, oh well but they live in "audio world" where is so many also other mysteries - in practice.I have never meet audiopeoples and becouse audio can listen directly but rf can not, im not so interest about these DC - audio things... so I have forget also this dBuAE (dB related touunloaded voltageAudioEngineers level)."for ex: 30dB radiation at 50 Mhz. It is never -30 dB"what is 30dB radiation at 50MHz. Related to what?dB itself is "nothing".You can tell there is 1:1000 radiation at 50MHz. (-30dB) Now I ask, how much it is?Or I can ask what is 1000:1 radiation at 50MHz. (30dB)But, example 0dBm, it is 1mW power, exatly.0dBm reads as level is 0dB relatefd to 1mWhow about -30dBm. It is 1uWIt (dBm) means, level related to 1mW.if there is level +6dBm power is 2mWif there is level -6dBm power is 0.5mWBut if we know reference level and not always tell it, we can of course tell level is +30dB (related to level what we know and what we are talking)Or just in lab talking my friend who knows what we are doing and he tell to me... take 30dB up... and I turn signal generator from -127dBm to -97dBmIf spectrum analyzer noise floor level is -100dBm and you have -60dBm signal, you see 40dB high peak up from noise floor.

author: Mr Simpleton
author_rank: Unknown
timestamp: August 07, 2013, 10:17:39 am
content: Do not rule out the Signal Houndwww.signalhound.comThe SA44B covers 1Hz to 4.4 GHzYes it do have its share of oddities and can be annoyingly slow but still a very powerful spectrum analyzer in a very small package. Amazing really that it can be powered from the USB port. Perfect when out in the field, and have the lap top along.I have it and it finds good usage in my lab! Bought it just prior the release of the Rigol 815. Had some buyers remorse, but after using it I like it more and more. The automatic phase noise measurment is nice, so is the built in demodulator.

author: kumar
author_rank: Contributor
timestamp: August 07, 2013, 10:31:04 am
content: Thanks a lot for your reply.I forgot to mention that it is dBm.So I conclude from your answer that;1) -100dB is the noise floor in the example I mentioned.2) The total amount of radiation is the difference bet. the noise floor and the peak ( in the example it is -60 dB.) So the total radiation is 100dBm -60dBm=40dBm. In dBuV it will be 40+107=147dBuvIs that correct?

author: Mr Simpleton
author_rank: Unknown
timestamp: August 07, 2013, 02:37:08 pm
content: Quote from: kumar on August 07, 2013, 10:31:04 amNo, you must be careful about the minus sign!0 dBuV equals -107 dBm, or -100dBm equals +7dBuV and if you increase the the level by 40 dB you have -60 dBm or +47 dBuVSo your statement 2 should read:-60dBm - -100dBm = 40 dB In dBuV it will be 7dBuV + 40dB= 47 dBuVCheers

author: jerry507
author_rank: Regular Contributor
timestamp: August 07, 2013, 04:33:02 pm
content: Could someone clue me in to what the difference is between a spectrum analyzer and a dynamic signal analyzer is? I tried to do some googling, found nothing explicit. All the documentation including app notes from Agilent just focus on basic sampling and fft theory.So are they just a spectrum analyzer minus the down-conversion? I'd probably be slightly less confused had I ever actually seen and used one.

author: olsenn
author_rank: Frequent Contributor
timestamp: August 07, 2013, 05:09:31 pm
content: QuoteThe words "Dynamic Signal Analyzer" (DSA) and "Spectrum Analyzer" are effectively synonyms. Some use DSA when referring to spectrum analyzers that are DC-Coupled and operate to (very) low frequencies; while others use them interchangably. These devices show the frequency content of an input signal. Network analyzers on the other hand, show both frequency and phase content, making them more useful; albeit much more expensive!

author: KJDS
author_rank: Super Contributor
timestamp: August 07, 2013, 06:13:53 pm
content: Quote from: olsenn on August 07, 2013, 05:09:31 pmA vector network analyzer is used to analyze a network not a signal. It provide a signal source and measures the vector response of the network that is connected to its test ports. A scalar network analyzer measures a network connected to the test ports, but only gives the amplitude information and not the phase. Just to confuse things, Agilents 8713 family of network analyzers are actually vector analyzers but don't display any phase information on the screen so you can only see the scalar performance.A vector signal analyzer measures the signal applied to it in the same manner as a spectrum analyzer, but also provides information about the complex modulation on the signal.I hope that's confused things a little more

author: kumar
author_rank: Contributor
timestamp: August 08, 2013, 05:30:01 am
content: Thanks a lot. It is clear to me now.A gentle request. Can you please explain me why 0dBuv is -107dBm?

author: ve7xen
author_rank: Super Contributor
timestamp: August 08, 2013, 07:11:53 am
content: Quote from: kumar on August 08, 2013, 05:30:01 amI'm not sure how much depth you need, so I'll try to briefly cover the several concepts at work for you.'dB' is a way to express a ratio between two quantities. In the case of dBuV, the reference quantity is 1uV, and any value in 'dBuV' is giving you a ratio versus that 1uV reference. For power quantities (watts), the relation is 10*log(P / Pr), where Pr is the reference quantity (in this case dBm means a reference quantity of 1mW). For amplitude quantities like voltage, we generally use the relation db = 20*log(V / Vr) where V is the measured quantity, and Vr is the reference (dBuV means a reference of 1uV). I believe this is purely so that a dB gain of 'n' on the voltage quantity also equals a dB gain of 'n' in power (you can note this in the post you quoted that a 7dB difference in power *or* voltage is the same difference in the other quantity). To go in reverse and get a quantity from the dB and reference value, for power, we can simply do 10^(db/10)*Pr, by basic algebra.So, to derive 0dBuV = -107dBm, one way to approach it might be to figure out how much voltage 0dBuV is, then use our system impedance (in this case assumed to be 50 ohms) to figure out how much power we've got (in watts), then go back to dBm using the relations above.0dBuV = 0dB vs 1uV10^(0/10)*1uV = 1 * 1uVSo we can see that 0dB is always a 1:1 ratio, and 0dBuV means we have 1uV signal amplitude. Assuming the system impedance is 50 ohms, we can use the power formula P=V^2/R to get the power this 1uV signal will dissipate in a 50 ohm load:P = V^2/R, V=1e-6V, R=50ohmP = 1e-6^2/50P = 1e-12/50P = 20e-15WNow we can convert this to dBm:db = 10*log(P / Pr), P=20e-15W, Pr = 1e-3Wdb = 10*log(20e-15 / 1e-3)db = 10*log(20e-12)db = -106.99 dBmBe careful not to confuse dBu (used in audio and does not have anything to do with 1uV) and dBuV.

author: kumar
author_rank: Contributor
timestamp: August 10, 2013, 06:58:34 am
content: Thank you for helping me.Have you come accross any free dB calculator ( for EMI applicaion ) which can be downloaded? The one by R&S is not of much help.

author: Psi
author_rank: Super Contributor
timestamp: August 10, 2013, 07:53:53 am
content: I'm sure someone will write some spectrum analyzer software for the hackRF(kickstarter) when it ships.With a 30 MHz to 6Ghz range it will probably be the cheapest thing out there.I have no idea what sort of performance you'd get though.

author: claude3386
author_rank: Contributor
timestamp: August 10, 2013, 12:10:59 pm
content: I'm not sure about the performance and availability outside China but for less than US$750 you have the Atten AT5010D.It cover up to 1GHz, no TG of course.http://atten.com.cn/yibiaoyiqi/pinlvceliangyiqi/pinpufenxiyi/bianxiesh/2013/0321/505.htmlEdit:Apparently there is a version with TG, the documentation is very poor, except the buttons description, no explanation how to use the DSA.http://www.atten.eu/atten-at5010d-1ghz-spectrum-analyser.html

author: Asgards
author_rank: Newbie
timestamp: September 05, 2013, 05:25:14 pm
content: Just to follow up on my own question, I can say that I bought the RF-Explorer as mentioned earlier in this thread and I am very happy with it. Its simple and easy to use even for a total beginner such as myself. It probably not especially precise but its sufficient for what I need.

author: tinhead
author_rank: Super Contributor
timestamp: September 05, 2013, 06:20:12 pm
content: Quote from: claude3386 on August 10, 2013, 12:10:59 pma year ago ATTEN sales manager told me "i don't want to sell that gear unless you accept this: the firmware does have serious issues and is really basic".That was of couse year ago, but i would recommend to ask ATTEN before any purchase. And yeah, i would for sure watch who is providing the unit, ATTEN told me that (year ago) there was no way for user to update firmware, so there is risk to get old stock when buying from any small shop (except ATTEN directly of course).Honestly, i really appreciate that they told me this, that was more than fair enough.