Spectrum analyzer  Rohde & Schwarz FSP 1093.4495.03 - Page 1
Forum section: electronics / testgear

author: gergard
author_rank: Newbie
timestamp: November 13, 2014, 04:42:25 pm
content: Sorry for my english, an acquaintance of mine, has a spectrum analyzer Rohde & Schwarz FSP 1093.4495.03, close to 20 kHz the ssb phase noise is slightly higher, this is normal?Could be a problem in the section power supply?

author: gergard
author_rank: Newbie
timestamp: November 13, 2014, 07:10:48 pm
content: Sample image

author: MiataMuc
author_rank: Regular Contributor
timestamp: November 13, 2014, 08:01:22 pm
content: Hi,this is how the same spectrum looks here..

author: rf-loop
author_rank: Super Contributor
timestamp: November 14, 2014, 07:47:41 am
content: Quote from: MiataMuc on November 13, 2014, 08:01:22 pmThis is why Rigol is so dirty cheap. Internal LO phase noise is just "terrible" (but relaated to price - still not so bad - imho)But also need note that different SA this kind of "phase noise" (better say total noise) measurement is not comparable if think phase noise. There is too many unknown things. One thing is BW filter shape, specially quite far away center freg. It is typically specified as -3dB points. (RBW 300 Hz means that + and - 150Hz from RBW filter center it have -3dB points. But after then... example from 1k or 10k or 20k from filter center. Where it is exactly specified and certified. (it means lot if try make precision phase noise measurements with SA)Other SA model filter "stop band" shape may differ lot of from other manufacturer SA or even in same model individual equipments.

author: Andy2
author_rank: Contributor
timestamp: November 14, 2014, 10:04:32 am
content: The Rigol 815 does suffer from poor phase noise (as does my Rigol 1030), but it's in good company - the Tek603 and the Signal Hound BB60 are in the same ballpark. However, my little Signal Hound SA44b amazes me. OK, it's not up to Ye Olde HP standards, but it puts in a pretty good phase noise performance. I'm not sure quite how it achieves this, as (AFAIK) it is built around the same off-the-shelf PLL's etc that other cheap instruments use.

author: KJDS
author_rank: Super Contributor
timestamp: November 14, 2014, 11:30:08 am
content: Anritsu MT8801B radio test set, far better than the Rygol, not close to the R&S.The Signal Hound gets to where it does with a lot of signal processing. I suspect that if you were to put in a very low signal next to a large one then it could get missed. I'll try that when I've got some time to spare.

author: Bud
author_rank: Super Contributor
timestamp: November 14, 2014, 03:17:22 pm
content: This is not phase noise that is in the screenshots here, this is the device's noise floor.

author: KJDS
author_rank: Super Contributor
timestamp: November 14, 2014, 03:22:55 pm
content: Quote from: Bud on November 14, 2014, 03:17:22 pmIt's a mixture of both. For the Rygol, it's almost all phase noise. For the Signal hound, it's almost all noise floor and software. For the rest it's a mixture.

author: gergard
author_rank: Newbie
timestamp: November 14, 2014, 03:56:29 pm
content: Returning to Rodhe & Schwarz, the small increase in noise between 10 and 20 khz is normal or is likely a defect?

author: KJDS
author_rank: Super Contributor
timestamp: November 14, 2014, 04:41:33 pm
content: From page 3 of the datasheet below, it's where I'd expect it to be, -91dBm typical average in a 300Hz RBW between 10kHz and 100kHz from carrier. If you reduce the video bandwidth you'll see the average level better.http://cdn.rohde-schwarz.com/pws/dl_downloads/dl_common_library/dl_brochures_and_datasheets/pdf_1/FSP_specs_en.pdf

author: G0HZU
author_rank: Super Contributor
timestamp: November 14, 2014, 08:04:14 pm
content: The DANL of some analysers will be severely phase noise limited down here and I think a lot depends on the leakthrough level of the internal LO and how clean the LO is.It looks like the DANL of the R&S analyser is phase noise limited although the specs for its DANL down here seem verynoisy on the datasheet. So probably the best thing to do is send the image to R&S for their comments. It might be OK.The Signalhound 44 has a first LO that runs just a few MHz away from the input frequency and its internal synthesiser (ADF4350?) uses a bank of dividers to divide down its LO from a few GHz down to a few MHz in the case of this test. So it is no surprise it has low close to carrier noise at low frequencies. But test it at a 1kHz or 10kHz offset up at 500MHz or a few GHz and its performance will be quite noisy.My old HP8568B just about matches the Signalhound here for DANL down at a few kHz when set to its DC coupled input and terminated in 50 ohm. It manages -145dBm/Hz at 0dB attenuation and is a class apart from the other mainstream analysers on this thread in this respect despite it being a 35 year old design.See the image below with the reference level set down at -40dBm instead of 0dBm. Note: I very rarely use this analyser down at low frequencies like this but I guess it's good to see it maintain a decent DANL right down to these low frequencies

author: videobruce
author_rank: Frequent Contributor
timestamp: November 18, 2014, 05:03:24 pm
content: Quote from: Andy2 on November 14, 2014, 10:04:32 amWithout getting to far OT, overall, other than the frequency capability of the 1030, where do you see the improvements over the 815, what parameters?

author: Andy2
author_rank: Contributor
timestamp: November 18, 2014, 07:13:40 pm
content: Videobruce - Well, you don't get as much as you might imagine. The extra Gigs are handy, and in addition you get extra RBW's of 30 Hz and 10 Hz. However, these are limited in their useability because of the high level of close-in phase noise as discussed earlier. There's also a set of more advanced measurement tools unlocked. Apart from that it's the same as the 815. RF performance is the same in all respects AFAIK.For doing very narrow-band stuff like crystal filters etc I use my Signal Hound SA44b which has much lower phase noise and RBW's down to about 1 Hz. The software for the Hound has so far been a right royal pain in the neck (poor ergonomics, crash-prone), but the forthcoming re-write looks very promising. If it turns out to be as good as it looks and manages to steer clear of crashes I could be tempted to move the Rigol on to a good home.There's a video of the re-vamped s/w on You Tube.Sorry to OP for veering off topic.