open source spectrum analyzer - Page 1
Forum section: electronics / projects

author: diyaudio
author_rank: Frequent Contributor
timestamp: December 21, 2015, 06:51:24 am
content: Anyone got good sources for a open source spectrum analyser with >= 2.5GHz bandwidth,I've been doing budget for saving, it looks like if I had to save up for one I would probably get it in 2018, these instruments are just to expensiveI've been studying lots of spectrum analyzer block diagrams, they seem deceptively easy to build once the fundamentals are grasped, but funny enough, it looks like you need own a spectrum analyzer to build and test a diy spectrum analyser.

author: ataradov
author_rank: Super Contributor
timestamp: December 21, 2015, 08:18:55 am
content: Quote from: diyaudio on December 21, 2015, 06:51:24 amThat must be a very high level block diagram. There is nothing easy about 2.5 GHz bandwidth.Quote from: diyaudio on December 21, 2015, 06:51:24 amThat's always the case. And that is something DIY oscilloscope makers often don't understand. Thankfully real scopes are now super cheap, so the flow of never-ending DIY project slowed down quite a bit.

author: Neganur
author_rank: Unknown
timestamp: December 21, 2015, 08:51:26 am
content: http://www.scottyspectrumanalyzer.com/msaslim.htmlThere's a yahoo group connected to this with gerbers etc. well worth the learning experience.But perhaps something like a CTRU from R&S is affordable too.

author: diyaudio
author_rank: Frequent Contributor
timestamp: December 21, 2015, 09:00:34 am
content: Quote from: ataradov on December 21, 2015, 08:18:55 amI have removed all fear and anxiety with spectrum up to 2.4GHz its nowadays "considered as DC"so vie taken a leap of faith to and started studying it.

author: diyaudio
author_rank: Frequent Contributor
timestamp: December 21, 2015, 09:02:01 am
content: Quote from: blueskull on December 21, 2015, 08:44:24 amthanks, I have been in touch with them I might be getting one of those.

author: diyaudio
author_rank: Frequent Contributor
timestamp: December 21, 2015, 09:04:32 am
content: Quote from: Neganur on December 21, 2015, 08:51:26 amThere is this project as well. but the project is still incomplete , good for learning.

author: ataradov
author_rank: Super Contributor
timestamp: December 21, 2015, 09:06:35 am
content: If having fun designing the thing is not a goal, then it is probably better to save money and take on some freelance jobs and get the real thing. I mean, it will take you at least a year to build one, if you can live without SA for a year, do you really need one?

author: Kalvin
author_rank: Super Contributor
timestamp: December 21, 2015, 09:46:57 am
content: You may want to look at the HackRF. It will go from 1MHz up to 6GHz with 8-bit dynamic range and max. 20MHz bandwidth. With a upconverter, you can cover lower frequencies too. You need external tracking generator as the HackRF is half-duplex only. Price is USD $300+ .Analog Devices has AD9364, a transceiver from 70MHz to 6GHz with 12-bit ADC/DAC and bandwith from 200kHz up to 56MHz. With a proper upconverter, you can cover the lower frequencies too. Interesting chip, and requires some signal processing logic to make it run. The chip itself costs USD $135.There may be some other devices that can be converted and tweaked to usable spectrum analyzer. Using modules from Mini Circuits and others may help a lot.Edit: Texas Instruments and Maxim has usable chips that can be used as a basis for a simple spectrum analyzer with proper up/down converters.

author: Marco
author_rank: Super Contributor
timestamp: December 21, 2015, 11:08:31 am
content: Quote from: Kalvin on December 21, 2015, 09:46:57 amThat has a square wave mixer doesn't it?

author: diyaudio
author_rank: Frequent Contributor
timestamp: December 21, 2015, 12:28:26 pm
content: Quote from: Kalvin on December 21, 2015, 09:46:57 amthanks, however for 300 I would prefer to save up for a signal hound.The AD9364 looks very interesting, inevitably no samples strange no sampling of the DDS chips, must be all the people making ebay kits.

author: Kalvin
author_rank: Super Contributor
timestamp: December 21, 2015, 01:43:00 pm
content: Quote from: Marco on December 21, 2015, 11:08:31 amYou mean Tayloe mixer a.k.a commutating mixer? No, according to documentation it uses RFFC5072 mixer/synthesizer:https://github.com/mossmann/hackrf/wiki/Hardware-Components

author: Marco
author_rank: Super Contributor
timestamp: December 21, 2015, 05:04:11 pm
content: Quote from: Kalvin on December 21, 2015, 01:43:00 pmWhich has a 2^n divider before the mixer, so yeah.

author: Kalvin
author_rank: Super Contributor
timestamp: December 25, 2015, 09:57:52 pm
content: This may be helpful to get started. See page 24: SDR-based 0 - 1.7GHz spectrum analyzer for less than $65.http://www.gnarc.net/wp-content/uploads/2015/02/Software-Defined-Radio-SDR-for-Amateur-Radio-2015-02-11.pdfBy adding a suitable downconverter, you can cover higher frequencies too.

author: awallin
author_rank: Frequent Contributor
timestamp: December 26, 2015, 09:52:29 am
content: Quote from: Kalvin on December 25, 2015, 09:57:52 pmsure it's cheap, but 8-bit or 48 dB dynamic range isn't that great...For Scotty's design, has anyone built it with a pure DDS for the agile LO?I've worked with the AD9912 with a 1 GHz clock and output up to 400MHz. But there are faster chips e.g. AD9914http://www.analog.com/en/products/rf-microwave/direct-digital-synthesis-modulators/ad9914.html#product-overviewwith a 3.5 GHz clock it could generate up to maybe 1.6 GHz.Anyway it would be interesting to hear what modules/components in the Scotty design are under development and which ones are limiting performance currently.

author: Neganur
author_rank: Unknown
timestamp: December 26, 2015, 02:55:30 pm
content: Quote from: awallin on December 26, 2015, 09:52:29 amThe design is finished, you can build it and it will workas specified.I'm not sure I understand your question. The 1st LO is agile (i.e. 1-2GHz) DDS based. The 2nd LO is fixed.The 3rd LO again is a DDS based agile 1-2GHz LO used for the tracking generator (or as signal generator etc.)By changing the filter path, changing high/low side mixing you can achieve the frequency ranges 0...1 GHz , 1...2 GHz, 2...3 GHz.What performance is it that you want to extend? From what I understand, it was originally a 0...1GHz swept SA.Trying to increase the bandwidth with the AD9912 is I think not going to work. Instead, you probably want a higher frequency LO and the used AD9851 DDS modules will still be sufficient.If it's phase noise you want to improve, most of it comes from the PLL in the first LO I think.Quote from: diyaudio on December 21, 2015, 09:04:32 amThis is essentially scotty's design, the person in the video does a great job at documenting his learning experience and own additions. (there are more episodes in his channel)Just don't forget that a used HP SA or something like a CTRU can be had for around 400€ if lucky. So it's really also a question of if you want to afford all the effort invested to get a DIY up and running. Signal hound isn't exactly cheap either.

author: Neganur
author_rank: Unknown
timestamp: January 13, 2016, 01:34:16 pm
content: There is currently a group buy in the making on the yahoo mailing list for scotty's spectrum analyser:QuoteIf you're interested, I'd suggest you join the mailing list and reply to the current thread regarding the purchase (it's called "Group buy of PCBs Winter 2016").