quite inexpensive test gear

[Opcom]

This seems kind of new: http://www.rigolna.com/

My boss found it and niether of us saw it last time we were looking for a spectrum analyzer.

I was comparing the DSA815-TG
http://www.rigolna.com/products/spectrum-analyzers/dsa815-TG/

to:

http://www.signalhound.com/SA44B.htm
(plus the tracking generator)


Each setup has different qualities.

[W4NEQ]

Probably pretty good for general purpose ham work, but don't expect it to produce the results of a 20-40K specan.  It will lie to you.  I recently paid about 20K for an Anritsu with tracking generator, and that was the cheapest I could find that had the noise and dynamic range performance required for broadcast measurements.  And I tested two others in the 8K-12K range that were entirely inadequate.   The Anritsu has very good RF performance, but software and ergonomics leave a bit to be desired.

Still, the Rigol is better than no specan at all.

Chris

[Opcom]

I require only 150KHz maximum in the work either one of these would be intended for. I think from the noise standpoint they will do. Maybe I can get a demo, there is a distribution/sales office 20 miles from work.

[Tom WA3KLR]

I just learned of this new equipment.  It looks very attractive for the hobbyist - $1495 for a 9 kHZ to 1.5 GHz spectrum anayzer with a tracking generator, other models in the family.

Here is the link to an electrical engineer geek forum thread on the Rigol DSA815.
Page 6 has some screen captures.  
A Rigol U.S. employee chimes in on page 7 :

http://www.eevblog.com/forum/product-reviews-photos-and-discussion/spectrum-analyzer-rigol-dsa815/

[N4LTA]

That looks like a very nice piece of ham equipment. Not lab quality, but most advanced hams don't need lab quality.

I am seriously considering it. Hmm - What can I sell?

Pat
N4LTA

[WA1GFZ]

The software guys are talking about doing VNA software for the Hermes module and there is hardware in the works to do a wideband spectrum analyzer/tracking generator for the Atlas project.
Look at HP8566B. Tucker will install a new LCD display and calibrate the whole thing for about $2K. You can sometimes pick them up for around $2K. This is by far the best spectrum analyzer made but kind of heavy so lab use only.

[W3RSW]

Best one of the bunch.
Really disses false or hidden noise floor/ bandwidth specs.
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Re: Spectrum Analyzer - Rigol DSA815

« Reply #13 on: April 10, 2012, 09:13:02 AM »

Quote from: echu on April 09, 2012, 11:28:52 PM

I am close to ordering signalhound for work. There are several reports on this (mostly by ham radio operators) that are impressive. Consider this is a USB instrument that is achieving -150 dBm sensitivity, which means roughly it is able to resolve ~picovolt level signals. If I get one, I will report back.

Quote from: echu on April 09, 2012, 11:28:52 PM

I am close to ordering signalhound for work. There are several reports on this (mostly by ham radio operators) that are impressive. Consider this is a USB instrument that is achieving -150 dBm sensitivity, which means roughly it is able to resolve ~picovolt level signals. If I get one, I will report back.

-150dBm in 50ohm system means that voltage rms  is around 7.071nV (7071pV)
dBm is power related to 1mW  (this m is for mW)

With 100Hz RBW it is (if -150dBm/Hz)  around -130dBm (dependent also littlebit RBW filter shape specs)

It need really understand what mean  this noise level. (DANL)
dBm/Hz !!!  And  even more, what really this average mean in practice working.
(DPNL is raw and hard... they (manufacturers) do not want use it)

(yes manufacturers do not always clearly tell this dBm/Hz... it is very fun example if minimum RBW is 1kHz or even more and manufacturer use dBmHz but talk dBm. Sometimes it is noted in one place with small letters and then they use without any worry just dBm. It is not clear lie becouse it really can find there if read all carefully. Some manufactures show it more clear some maybe forget whole thing.

What it means?

If it is -150dBm/Hz   what if band  width (RBW) is 100Hz. It is -130dBm
What is displayed noise level in practice if RBW is 1kHz or 100kHz.
It is good to know and realize so disappointment is then not so big.

What span it is practical to use 100Hz RBW. How long time it take if set span example 100MHz and use 100Hz or 1kHz or example 10kHz RBW. (with 100kHz filter it takes around one second!  So it is really amazing slow! Old (very old) and slow R&S take same 40ms. With 100MHz span and RBW 100kHz and input attenuator 0dB. With this setting noise peak level is around -100dBm compared to this dogbox -65dBm. (oh well 35dB difference, not so big... more than 1000:1 in power )

And this: "Frequency Sweeps up to 140 MHz per second"

There was one example picture in rewiew, 100MHz span, 100kHz RBW  sweep time nearly 1 second
and noise peak floor seems be around -65dBm  and maybe under -70dBm level can not detect anything.  It is realistic. (with these used settings)

Then this people who make rewiev and he look dislpayed average noise level... he use 100Hz RBW and then he adjust (normalize) numbers to dBm/Hz (dBm/1Hz) this is natural becouse also manufaturer use this, but it need remember what is dBm/Hz. Minimum RBW in this box is 100Hz.

Residual spurious in input connector! Level is -- more bad than terrible. After reading this, if I see any serious lab work made with this box... I classify it as "garbage".

But then, price! In this price: not bad for many kind of use where is not so critical for perfomance and accuracy.

In manufacturer AD they tell it is high perfomance spectrum analyzer. (    )

If this is High Perfomance spectrum analyzer I'm caesar of China.
It is low perfomance or entry level/hobby level spectrum analyzer but maybe not toy level.

« Last Edit: April 10, 2012, 09:41:00 AM by rf-loop » "

[Opcom]

The above quoted thread title was about the Rigol, but the talk in that post was about considering the signal hound. Which instrument is the quoted poster complaining about the marketing of?

[Tom WA3KLR]

The guy "rf loop" you are quoting Rick said in a later post that the DSA815 is reasonable unit in that $1000 class price range.  In another post also after his -150 dbm rant, another engineer talks about the law of physics in regards to low BW and low video bandwidth filtering.  You can't get away from long sweep times when both the IF BW and Video BW are cranked down.  

Displayed Noise Level - People need to go back and review the theory on Noise Figure, noise, bandwidth, etc.  The unit talked about here is the DSA815, the lowest member of the Rigol SA group.  The best member is the DSA1000A class.  The DSA800 family lowest spec on DANL is -135 dBm.  The DSA1000A class has a spec of -148 dBm in one set of conditions.  These specs are at 100 Hz i.f. BW, 10 HZ Video BW, AND greater than or equal to 50 TRACE AVERAGING, a very heavy filtering tool.

Trace averaging is a powerful filter.  Anyone who has ACTUALLY USED a digital scope and has cranked in the trace averaging knows what I mean.  This will really pull a bump out of the noise.  What the EFFECTIVE net BW of all this is, I don't know.  But let’s consider it brings the effective bandwidth to 1 Hertz.  In a 50 Ohm system, 0 dB noise figure, 1 Hertz bandwidth, the noise floor is -174 dBm.  If the analyzer can display a -148 dBm noise floor, this means the analyzer has a 26 dB noise figure.  The noise figure is probably better than this.  The numbers may not correlate well, but my point is that the DANL numbers quoted are not nonsense, they are quite reasonable.  They only appear unreasonable to people who are not used to very low bandwidth applications.  

It would be interesting for the first guy here to get his hands on a Rigol spectrum analyzer to put it on an r.f. signal generator with the i.f. and video BW cranked down and the trace averaging cranked in and see how low of a carrier he can resolve.

[W3RSW]

I know Tom, but I thought it was funny for several reasons, not just model or manufacturer specific. The whole point is that you can't get something for nothing.  Even with analog sampling, integration takes time.  Well we're not drilling down to the quantum domain here to explain it, but if one unknown is pinned down then another is "suddenly" more vague. It takes time and more samples, or more rapid sampling rate, etc. to nail down with a degree of precision.  Time is not separate but an intimate part of the process.

I thought the guy made some good points about manufacturers' hype.

[WD5JKO]

I recently purchased a spectrum analyzer for work. My requirements were not too stringent; just needed to look at the AM modulation, and harmonic output of a 3KW 13.56 Mhz commercial brick.

The budget was tight, and whatever we chose needed to undergo annual ISO calibration with cal sticker, and a test sheet that would satisfy an ISO auditor. My company likes Newark, so we ordered the Tenma 72-6696. What a nightmare, since Newark could not deliver, and after two months they got a unit and sent it to their cal lab. The Tenma would not meet spec's, so they tried another, same. Newark would not cancel or change the order until we got VERY nasty with them. We finally got them to switch to the B&K 2630, and here too there was calibration issues causing delays. Finally after nearly three months we got a delivered unit.

So whatever you choose, if you need a calibration sticker, the bottom end spectrum analyzers are closer to toys, and therefore may not pass calibration, and if they do, may not hold those specifications for very long.

I wonder how those USB analyzers would fare in a cal shop?

Jim
WD5JKO

[W7TFO]

I'm working in San Diego for a summer respite from the Phoenix heat, and have used that Rigol analyzer.

Beats the pants off my Agilent portable, the only shortfall in no battery power.

A real bargain.

73DG

[Opcom]

Tom, The 815 Rigol model has been ordered for me to use at work. I have a 50MHz function generator, that's about it for carrier-makers. When it shows up, I could give that a spin.

[N4LTA]

Let us know as it looks real interesting to me. I am still using a 75 pound HP beast.

Pat
N4LTA

[WD5JKO]

No-one commented concerning calibration of "inexpensive test gear". Case in point, at the shop we use a AEA "VIA" antenna analyzer similar to this:

http://www.k1cra.com/catalog/product.aspx?productID=780

This item can be had for about $600, and is adequate to our needs. Problem however being an ISO 9001 company, we must have calibration stickers on all the test equipment. The cal lab we use charged $850 last year to get a 12 month sticker.  

Similar story on the DVM's...Now we have a pile of them that we cannot use since they are not getting stickers, and instead are hidden in a cabinet somewhere.

Buying brand new stuff DOES NOT come with calibration...that is extra.

What is going on with the cal labs?

Jim
WD5JKO
 

[WA1GFZ]

There has been first release of VNA software for Hermes.
I don't know about phase accuracy but amplitude is in line with eveything I own.

[W3RSW]

Like everything else, technology will make an end run around all the guilds including cal labs in cahoots with the FCC and other city/state/nations' regulating bodies.

-Necessary at one time, rapidly becoming superfluous.  Lawyers, Dr's., elect. techs, engineers with all their specialized equipment and knowledge bases,....  you name it.  High quality people, gear and procedures will always in demand, just far fewer, certainly not in the quantities needed in the past.

In my field and similar, there's always been an industrial expemption for registered engineers.  Only when 'serving' the public has registration/testing/certification been required.  So at least one function had some sense over the years.

[WA1GFZ]

registration/testing/certification provides high paying jobs for otherwise unemployable idiots.
In the real world if you do a job then you keep the job

[W3RSW]

Sounds like you've run across a few.   

[WA1GFZ]

yes about once a week

[Opcom]

There is no telling what the Rigol will cost to calibrate. It's a $1600 equipment so it should not be much.

To calibrate it, it goes to the importer's lab and a tech or engineer connects it to some ATE that is traceable and runs some software. 5 minutes later it is either calibrated or I get an e-mail saying it needs repair. There is probably nothing physical to adjust inside it.

[WA1GFZ]

Check into calibration costs before you purchase. I would avoid anything that has to go back to the factory. Shipping costs, potential shipping damages and no competition will suck money out of your wallet more than the cost of the instrument.