When trying to measure the spurs of a SI5351 the first measurement caused some doubt on the performance of the tinySA.
Is the output of the SI5351 really that bad?
The output of the SI5351 is connected to the input of the tinySA using a 20dB attenuator
Output frequency of the SI535 is set to 135MHz.
A signal 346.6 MHz appeared and this should not be there because the LO low pass filter is still present and it has no direct harmonic relation to 135MHz



Then I remembered my own advice. Always use a 10dB attenuator to test if the harmonics you see are really part of the input.
This led to a much improved measurement, all harmonics above 150MHz are now suppressed.



The spurs around 135MHz are caused by the fractional divider in the SI5351 but what is causing the 76.6MHz and 211.6MHz signals?
Time to switch on the spur reduction. And that made a big difference.



The?76.6MHz and 211.6MHz signals are (almost) gone and this measurement is very much like when using a much better SA.
So keep in mind when you build and use the tinySA: it is easy to get wrong measurement results!
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HBTE Files section:?/g/HBTE/files
Erik, PD0EK

And here is an example where the tinySA fails miserably
Sweeping the signal from a small antenna between 0 and 200MHz?



The DAB transmission at 190MHz is recognizable but the FM band around 84MHz is very bad. As the tinySA still has no input low pass filter we are actually seeing an alias of the 950MHz signal from a nearby mobile phone base station. The same is true for the hump around 30MHz
Time to build a low-pass filter
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HBTE Files section:?/g/HBTE/files
Erik, PD0EK

Adding a 110MHz low pass filter at the input (almost) solved the problem
Here is the FM band using a small antenna


Still a bit of a hump below 90MHz
--
HBTE Files section:?/g/HBTE/files
Erik, PD0EK

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YES, same here.
If anyone figures out how, please post.
I don't want to buy the $300 software to run a $35 device...
Have tried downloading two .dll files it needed, installing free VisualStudio, Windows7,
nothing..? Current problem is complaint about entry point to the crt in the downloaded dll...
73,
Gary
WB6OGD

I found a bug causing the tinySA SW to crash on certain PC configurations during startup
The bug is solved in the updated SA.zip file in the files areas
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HBTE Files section:?/g/HBTE/files
Erik, PD0EK

Have you given any thought to a version with 868MHz IF?
As thats also a common ISM band and filters for that are available.

For a 868MHz IF you would need? a LO module with 1736MHz maximum frequency in order to be able to exploit the whole range.
You could use the SI4432 with a 868MHz IF but as its maximum output frequency is about 960MHz you would only be able to scan from 0MHz till below 100MHz. Or you would have to switch to below IF scanning creating all kind of mirror problems.?I could not find a cost advantage either.
The special thing about the SI4432 is its continuous sweep range from 260MHz till 960MHz and the SSI with 120dB range. most other designs are banded creating gaps in the range they can cover or have less range in the SSI

Of course, if you are willing to pay more you can use very different components with very different performance, but that is not the subject now.
--
HBTE Files section:?/g/HBTE/files
Erik, PD0EK

开云体育

Will investigate how to do an installer
--
HBTE Files section:?/g/HBTE/files
Erik, PD0EK

I uploaded a new SA.zip file containing additional error checking and reporting.
Can you try?
--
HBTE Files section:?/g/HBTE/files
Erik, PD0EK

开云体育

开云体育