Checking the attenuator

First connect the HIGH and LOW connectors using one of the supplied SMA cables.

Switch on the tinySA and enable the CAL output at 30 MHz using the commands MODE/Cal Output/30MHz.

Return to LOW input.

Activate the linearity test with MEASURE/MORE/LINEAR and this will step (0.5 dB) the built-in attenuator through all attenuation values and draw a green line on the screen at the measured signal level. If all goes well the line should be flat within +/- 1 dB with an occasional measurement deviating due to interference/noise.

attachment:linear.jpg

If you observe deviations in the green line of more than +/- 1 dB (excluding some noise/interference) post a readable picture or screen capture of the screen of the completed linearity test on the tinySA support group.

The test also helps in getting confidence about the 1 dB compression point of the tinySA. This can be measured by applying a signal of 0 dBm and activating the MEASURE/MORE/LINEAR test The compression starts when attenuation is below 2 dB and is just visible in the green line being curved down a bit at the right side because of the compression.

attachment:compression.jpg1

I used a Spectrum Analyzer LTDZ tracking generator to connect a +0.7 dBm 34 MHz signal to input LOW, see the screenshot below.

attachment:tinySA_Compression1.jpg1

At an attenuator level of 20.0 dB the input level shows +0.2 dBm. attachment:tinySA_Compression.jpg2

At an attenuator level of 10.0 dB the headline turns from color green to red.

The Red color shows, that at this input level, after attenuation, is starting to overload the tinySA and is creating internal harmonics.

The green line stops at an attenuator level of -500mdB (cosmetic, in reality 0 dB), the input level shows then -0.8 dBm. attachment:tinySA_Compression.jpg3


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TinySA-CheckTheAttenuator (last edited 2021-01-21 21:35:43 by RudolfReuter)