Learning to use a Spec An - Page 1
Forum section: electronics / beginners

author: jgalak
author_rank: Regular Contributor
timestamp: April 06, 2018, 07:16:48 pm
content: I just pulled the trigger on a Spec An (Siglent), but have only a vague idea of how to use one, having never had access to one before. The closest I've come is the fft mode on a scope and an SDR's panadapter display. I understand the general principles - showing signals in the frequency domain - but I'm sure there much more to getting the most out of it.Other than the manual, can folks recommend resources for learning how to use this instrument? Online or available as e-books, pteferably.I've seen several of w2aew's videos where he uses SpecAns, but most of those (except #51) are application-specific. I'm looking for a broad introduction to the instrument.

author: 0xfede
author_rank: Regular Contributor
timestamp: April 06, 2018, 08:06:37 pm
content: Hi jgalak,here are a few documents concerning the basis behind a spectrum analyzer:http://www.hit.ac.il/.upload/engineering/experiment_1_spectrum_analyzer.pdfhttp://www.ee.iitm.ac.in/vlsi/_media/courses/ec330_2009/5965-7920e.pdfhttps://indico.cern.ch/event/115334/sessions/5217/attachments/50210/72213/C1_Piotr_Ex_all.pdfhttps://www.keysight.com/upload/cmc_upload/All/02-18-03-B2B-RF-SpectrumAnalysis-Thomas-Holmes-Hightower-839.pdfhttps://www.naic.edu/~phil/hardware/Misc/anritsu/SpectrumAnalyzer_basis_of.pdfhttps://cdn.rohde-schwarz.com/pws/dl_downloads/dl_application/application_notes/1ma201_1/1MA201_9e_spectrum_analyzers_meas.pdfJust out of curiosity, which is the main purpose of your new device? Are you interested in a particular band/application?Best,0xfede

author: jgalak
author_rank: Regular Contributor
timestamp: April 06, 2018, 09:10:48 pm
content: Quote from: 0xfede on April 06, 2018, 08:06:37 pmMostly applications related to ham radio. My current project is designing and building an APRS tracker. Which means I need to do things like look at the quality of the output of the transmitter, verify that the filter I designed is performing appropriately, examine the quality of the PA, etc.

author: rob.manderson
author_rank: Regular Contributor
timestamp: April 06, 2018, 10:01:08 pm
content: I'd hope it goes without saying but I'll say it anyway!Be careful of the input - if you're hooking it up to a transmitter be sure you know the approximate power output and make sure you're using an attenuator to bring the power at the input well below the maximum the SA can take. Forget just once and it'll ruin your day AND the input mixer.

author: jgalak
author_rank: Regular Contributor
timestamp: April 06, 2018, 10:33:35 pm
content: I do know that, but thanks for the reminder!I have some attenuating couplers I can use (10dB and 20dB) and I'm aware of the issue.My current transmitter, which doesn't yet have a PA stage, puts out a theoretical maximum of 15 dBm before any filters, which is well below the SpecAn's max rating of 30 dBm (as long as preamp is off and attenuator is set to max). In practice, trying to use an RTL-SDR dongle as a poor-man's SpecAn, I get a peak far, far lower than that (but it's also a very dirty signal - a square wave - so the energy is splattering all over the place).Still, the first time I hook it up, I'll probably use the 20dB coupler, just to be safe.

author: tautech
author_rank: Super Contributor
timestamp: April 06, 2018, 10:52:29 pm
content: Quote from: jgalak on April 06, 2018, 10:33:35 pmExactly what I did with mine before becoming more confident in its use.Study the SSA3kX thread:https://www.eevblog.com/forum/testgear/siglent-ssa3000x-spectrum-analyzers/In particular the posts and screenshots by rf-loop.All the little indicators on the display are strong clues for the settings used. He also links a few worthy documents to help the SA user to better understand principles.When you come across this vid by Shahriar using a SSA3kX take note and watch too !

author: jgalak
author_rank: Regular Contributor
timestamp: April 06, 2018, 11:04:50 pm
content: Thanks!That thread was a big part of why I decided to go with Siglent, but I'll be sure to go through it with a more immediate interest

author: tautech
author_rank: Super Contributor
timestamp: April 06, 2018, 11:32:36 pm
content: Quote from: jgalak on April 06, 2018, 11:04:50 pmFamiliarity with your instrument is my greatest recommendation along with an understanding of what you're trying to measure. Always be conscious of RF input levels and know the ways to manage them. Know how to use the input attenuation, -20dB is the default value and up to -51dB is available but IIRC there's a time limit on how long you can use max attenuation for. RTFM.When you get bushed (lost) in the UI (and you will) the Preset button is an escape that returns settings to default where you can start again with more purpose. The Preset can be user defined but for the novice I don't recommend it until you really know what you're doing. Until then use it as an escape from being tied in knots.Have a dig into the UI and find how to Invert the saved screenshots so you get the nicer black background version instead of the kucky white one.Little steps build confidence and understanding so apply the KISS principle for a bit. Trying to cram it all in is hard work for the SA novice so just get the simple stuff sorted until that becomes second nature......that's only about where I am as I only pull mine out every couple of months.Sort out the documents and vids that are of note and make sure you can easily find them when you need to take further steps into this fascinating world of spectrum analyzers and RF stuff.Enjoy.