Software Spectrum Analyser?

halfwave · Post by **halfwave** » Tue Nov 15, 2016 1:44 pm

Hi,

Does anyone know of a good free Software Spectrum Analyser
that runs on Windows 7?

As I would like to see how clean my transmitters signal is.

Also, along with the software is there a USB dongle device that I would
require to allow the software to pick up my signal?

Albert H · Post by **Albert H** » Tue Nov 15, 2016 3:09 pm

There is NOTHING good (free or otherwise) that runs on Windows anything!

That said, there are some of these SDR (software Defined Radio) dongles that you can get for about £20 from Ebay, and if you look around some of the amateur radio sites, there are various links to software for basic analysers. However, you'll find that most of the software is written for use under Linux since more recent versions of Windows don't allow the use of "uncertified" hardware. You need to get the right dongle for the software, of course!

thewisepranker · Post by **thewisepranker** » Tue Nov 15, 2016 4:38 pm

You won't get one for free as you need some kind of hardware to interface between your (heavily attenuated) transmitter output and the computer.

Albert H · Post by **Albert H** » Tue Nov 15, 2016 4:55 pm

http://www.rtl-sdr.com/rtl-sdr-wide-spectrum-analyzer/ uses the cheap "RTL" USB dongles> I have no need of this, as I have a couple of real analysers, but I found that one of the TV receiver dongles I bought was an "RTL" type, so I tried out the software.

It's actually a capable analyser up to about 1GHz - not bad for a £12 TV receiver USB stick!

Maximus · Post by **Maximus** » Tue Nov 15, 2016 10:02 pm

I've used SDR Sharp as a scanner to decrypt the local DMR town radios. It works quite well.

I've never used it as an analyser as it probably won't be accurate enough. The software is definitely capable and works on win 7.

There's plenty of videos on YouTube:
https://youtu.be/IaKEYEyrRgk

Software download:
http://airspy.com/download/

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halfwave · Post by **halfwave** » Wed Nov 16, 2016 1:38 pm

Hi All,

Thanks for the info and link etc.

I colleague at work suggested HDSR http://www.hdsdr.de/screenshots.html
which I guess would be similar to what has been previously suggested.

Maximus:
If all I want to do is see if my transmitter is producing harmonics / spurs on other frequencies, would these software Analyzers be able to show this? Considering I will be using them within
the same vicinity as by transmitter.

Maximus · Post by **Maximus** » Wed Nov 16, 2016 11:03 pm

halfwave wrote:Maximus:
If all I want to do is see if my transmitter is producing harmonics / spurs on other frequencies, would these software Analyzers be able to show this? Considering I will be using them within
the same vicinity as by transmitter.

Yes the chances are it'll pick up harmonics. Due to the way they're built, harmonics may show up that aren't actually there as well.

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Albert H · Post by **Albert H** » Wed Nov 16, 2016 11:57 pm

halfwave wrote: If all I want to do is see if my transmitter is producing harmonics

Build an absorption wavemeter. It'll cost you about £15 in parts (if you have to buy them all in) and will show you the existence of any harmonic energy. I used one for many years before I could afford a spectrum analyser.

Maximus · Post by **Maximus** » Wed Nov 23, 2016 2:41 am

I've just had a quick play with the ole dongle. Can anyone please tell me why there's a spike at the end of the carrier?
There's also a smaller one the other end

Please let me know if the picture doesn't upload

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Maximus · Post by **Maximus** » Wed Nov 23, 2016 2:53 am

Here's another picture of the left hand side of the carrier

halfwave · Post by **halfwave** » Mon Nov 28, 2016 11:49 pm

I have now been playing around with HDSDR and have a question, don't know
if anyone knows the answer?

If I go to my broadcast frequency and have it displayed in the "centre" of the frequency scale
(as shown in Image 1), it shows the main peak on top of a raised area (sorry for
the non technical description).

If I then slide the frequency scale a long a bit to the left the main peak is still there but
now I have two raised areas either side of the main peak. (as shown in Image 2)

If I then slide the frequency scale a bit more to the left, I then get the main peak
with a flatter terrain either side. (as shown in Image 3).

Obviously the main peak stays on the transmitted frequency, but I don't understand
why the spectrum pattern changes when I move the scale along, surely it should show
the same pattern with the whole display just moved over to the left, not actually change
the shape of the pattern!

Image 1

Image 2

Image 3

Maximus · Post by **Maximus** » Thu Dec 15, 2016 11:16 am

If you've got an extra £10-£15 spare, these dongles are supposed to be far superior.

http://www.nooelec.com/store/nesdr-smart.html

Discussion about them in good detail:
https://www.satellites.co.uk/forums/thr ... es.169600/

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