On Tue, May 5, 2020 at 07:28 AM, Kurt Poulsen wrote:

Hi Erik

I downloaded the ? and when starting it reports MSVCP100D missing. As far I have figure out it is a file implemented in the code for debugging code created with Visual Studio 2010.

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Internal flash allow minimum 10k write cycles (as in datasheet)

Possibly use external SD card for this, and use simple SPI transfer mode (easy connect to display SPI bus)

Then I tried to reproduce the measurement of Tom by setting my SI5351 to the same frequencies.
That failed as my SW for setting the SI5351 probably works in a different way.
Here I have two measurements that show the huge impact of changing another output

First the outputs are set at 45, 80 and 160MHz, all multiples of 5MHz.



Then I moved the 160MHz output to 161MHz



This seems to suggest you can not compare any SI5351 measurements unless you replicate the exact settings of the 2 VCO's and the 3 factional output dividers.

Reading this I got worried about the tinySA seeing ghosts so I took a SI5351 and set all outputs to 5MHz



A nice clean scan, except for the signal just above 8MHz which is probably a spur coming from the MCU in the tinySA

Then one of the unconnected outputs was set to 6MHz



Now various 1MHz spaced spurs appear

and with all outputs set to 6MHz



so the 1MHz spaced spikes seem to originate from the SI5351, or am I missing something and is there a big problem in the tinySA?

Would something as shown in this post help?
/g/tinysa/message/37
The scan speed in zero span can be set but the upper bandwidth of AM demodulation is about 1kHz (maybe 2kHz)?
After measuring the scan can be paused and later the tinySA can be connected to a computer to grab the screen
I do not yet foresee saving scans to flash as I'm not sure how many flash writes can be endured

Greetings Erik,?

? ? ? ? ? ? ? ?Further to my first message in this thread I have become aware that there are small, inexpensive pocket size battery powered oscilloscopes available with trace storage capabilities. Possibly a small portable scope could work well in conjunction with the tinySA to provide a time domain display with signature storage capabilities.

? ? ? ? ? ? ? ?I wonder if during zero span mode if it would be possible to connect an external scope for time domain viewing the linear amplitude characteristics of the signal being monitored? IMHO it would be a useful feature.

Best Regards,
Tom, VA7TA

Greetings Allison,

? ? ? ?Very interesting info - thanks!

? ? ? ?I also did some tests with all three outputs of the Si5351 active and terminated. It is a couple of years ago thus the details are now a bit foggy. Attached is a screen capture obtained from the CLK0 output with the three terminated outputs set to 45, 145 and 160 MHz. The span was set to 400 MHz and of course the higher amplitude spurs are the harmonics of the 45 MHz fundamental.? As you mentioned there is quite a large number of intermodulation spurs around 55 to 65 dB down which appear to be generated by the mixing of the three output signals. The crosstalk from the 145 MHz output is about 42dB down and somewhat surprisingly the 160 MHz coupling is down around -60 dB. There was a rather strong intermod spur at about 22 MHz at only 42 dB down.?

? ? ? But what I notice different in this case regarding the tinySA spectral purity screen capture is that unlike the triple output spectrum I captured the spurs look evenly spaced at similar levels across the spectrum which gives me the impression they might be from low level modulation. It makes me wonder if there was an external influence such as digital noise riding on the Si5351 power/ground rails that resulted in low level modulation sidebands.

? ? ? For interest sake back then while I had the analyzer setup I apparently also measured the signal from a single output Si570 generator set to 100 MHz. It sure looks like a nice LO signal in comparison, (:/).

Best Regards,
Tom, VA7TA

Yes, that is an issue with 5351 if more than one output is used.

That is the circulating current on the ground and substrate of the chip
where in both cases there is finite resistance however small and with a?
50 ohm load on a pair of outputs its easy to see the other oscillator at
its discrete frequency at 56-60db down from the other and sometimes
even the sum and difference.? IF the load resistance is higher say 1K
then the amount of current at each output goes down and so do the
undesired products.

Its one of the things that will define the maximum dynamic range
over some span.

The other area is the mixer its IP3 is better defined but never the less real.

Also any LC filters used depending on their construction and specific
components can also contribute IP3 elements.

Allison
-----------------------------------------
Please post here, direct emails go to a dead letter box.

Erik,
? ?Thanks for considering the feature request.? If you are running out of menu slots and can squeeze in dBuV and dBmV then between those units and dBm you will be covering the majority of testing limits that I have encountered in my test and measurement career.??

- Herb

Making the scale change and the display of the values of the markers was the easy part, now the behavior has to change as Watt and Vrms can not go negative and I'm running out of scale menu slots

Also a potential tester..

Comparison gear HP8568B, tough to move but a great instrument
the other is Rigol DSA815T? portable without back pain.

Experience with the larger HP line like 8590 and? R&S FSH6 portable.
?Plus building my own in the analog era.

Allison/Kb1GMX

Erik,
? ?I know it late in the game and all firmware features are probably already set in stone.? I was just wondering if you would consider, in a future firmware release, adding? dBmV, dBuV, Volts and Watts as menu options to dBm for Y-axis unit display.

? Where? dBm, dBmV, and dBuV are for Log scale; Volts and Watts are for Linear scale with the default Y-axis display unit as dBm.? This is a fairly common menu option on most of the spectrum analyzers I have used in the past.? If you don't support linear scaling then would you consider dBmV and dBuV menu options?

? The unit conversions can be performed manually by the user but being able to select them as a tinySA menu option would be a useful feature.

- Herb

On Sun, May 3, 2020 at 12:21 PM, Jim Allyn - N7JA wrote:

I see Kurt beat me to it.? Note to self: check to see if there are other replies before responding.

Jim,
? ?Thanks for chiming in.? Yes, both Kurt and Erik responded.? Don't let it stop you from adding any other useful insights you have regarding the tinySA.? Its really shaping up to be another useful instrument in the same vein as the NanoVNA that hams and hobbyist didn't have in their toolbox just a couple of years ago.

? ?Attached to a computer and with additional EMC related accessories, it will be interesting to see how it shapes up as a pre-compliance measurement system below 300 MHz.

- Herb

I see Kurt beat me to it.? Note to self: check to see if there are other replies before responding.

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On 5/3/20 6:36 AM, hwalker wrote:

the 50 and 75 MHz harmonic marker amplitude values are off by 15 dB

It looks like the 50 and 75 MHz level might be relative to the 25 MHz level.

Well...
Untill 4 days ago I did not know about dBc. Will change unit when switching to relative marker

On Sun, May 3, 2020 at 07:16 AM, Kurt Poulsen wrote:

Hi Herb

It is relative to the carrier level ?

Kind regards

Kurt

?

Thanks Kurt. I didn't consider that.? I'm used to seeing dBc units for measurements relative to the carrier level.?

Herb

?

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