open source spectrum analyzer

[diyaudio]

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 expensive


I'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.   

[ataradov]

they seem deceptively easy to build once the fundamentals are grasped,

That must be a very high level block diagram. There is nothing easy about 2.5 GHz bandwidth.

but funny enough it looks like you need own a spectrum analyzer to build and test a diy spectrum analyser.

That'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.

[Neganur]

http://www.scottyspectrumanalyzer.com/msaslim.html

There'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.

[diyaudio]

they seem deceptively easy to build once the fundamentals are grasped,

That must be a very high level block diagram. There is nothing easy about 2.5 GHz bandwidth.

I 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.
 

[diyaudio]

A toy SA with a crappy RF frontend and a SDR chip, such as these triarchy ones might work, as low as <$400.
A better but more expensive one can be the Signal Hound USB-SA44B, a 4.4GHz real time I/Q demodulating SA, list price is $1000.

thanks, I have been in touch with them I might be getting one of those.

[diyaudio]

http://www.scottyspectrumanalyzer.com/msaslim.html

There'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.

There is this project as well. but the project is still incomplete , good for learning.

[ataradov]

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?

[Kalvin]

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.

[Marco]

You may want to look at the HackRF.

That has a square wave mixer doesn't it?

[diyaudio]

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.

thanks, 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. 


 

[Kalvin]

You may want to look at the HackRF.

That has a square wave mixer doesn't it?

You 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

[Marco]

You mean Tayloe mixer a.k.a commutating mixer? No, according to documentation it uses  RFFC5072 mixer/synthesizer:

Which has a 2^n divider before the mixer, so yeah.

[Kalvin]

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.pdf
By adding a suitable downconverter, you can cover higher frequencies too.

[awallin]

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.pdf
By adding a suitable downconverter, you can cover higher frequencies too.

sure 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. AD9914
http://www.analog.com/en/products/rf-microwave/direct-digital-synthesis-modulators/ad9914.html#product-overview
with 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.

[Neganur]

[...]

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. AD9914
http://www.analog.com/en/products/rf-microwave/direct-digital-synthesis-modulators/ad9914.html#product-overview
with 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.

The design is finished, you can build it and it will work as 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.

http://www.scottyspectrumanalyzer.com/msaslim.html

There'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.

There is this project as well. but the project is still incomplete , good for learning.

This 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.

[Neganur]

There is currently a group buy in the making on the yahoo mailing list for scotty's spectrum analyser: 

OK, I think we need to find out what the demand is.  Depending on the number, each panel cost will be from 35-75 dollars.  If you could respond by answering the following:

1. MSA board with all PCBs to complete to VNA level.

2. Accessory board.  Details are in the spring 2012 group buy postings.

3. Mini circuits kit

4. There is also the option to use a SAW filter in place of the cavity filter(on accessory panel),  group buy from http://www.golledge.com/

[...]

Stew
KF5KOG

If 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").