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SSA2021X - 20 dB attenuator sufficient?
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tautech:

--- Quote from: fnaumann on February 08, 2024, 11:54:15 pm ---I did my own testing with my SSA2021X and TinySA Ultra using a test signal from my SDG 1032X.

The signals were clearly visible on the TinySA Ultra out of the box. With the SSA2021X, the signal was also visible after various adjustments, but with significantly more noise. The signal/noise ratio seems scary to me as a layman. I tried to set the SSA2021X using various options so that I could see the test signal better on the display. As a test signal I used a simple 10 MHz sine wave signal with 1 to 5 dBm output level (SDG 50 ohm output mode).
To protect the SSA, I installed a 30 dB attenuator (10 W) plus a DC blocker. I reduced the internal attenuation to 0 dB (after the signal-to-noise ratio didn't improve much). Which doesn't make it much better. Then when I activated the internal preamp, the SSA beeped and warned of an overload situation. What crap. The SSA is specified as a maximum of 30 dBm and 50 V DC. Of course, these values are only given for special settings.

BUT - I had used a maximum of a 5dBm signal with 30dB of external attenuation, which corresponds to a -25dBm signal. How can a -25dBm signal produce an overload warning on the SSA? I only activated the PreAmp option under “Amplitude” without setting a manual value. Shouldn't the software prevent overload?

--- End quote ---
TBH this is incorrect methodology.
Instead you should let the SA manage internal attenuation and add external attenuators when/if necessary.
External attenuation can then be nulled/corrected with use of the amplitude offset feature.

Post a screenshot up and lets compare settings.
fnaumann:

--- Quote from: tautech on February 09, 2024, 12:00:26 am ---Instead you should let the SA manage internal attenuation and add external attenuators when/if necessary.
External attenuation can then be nulled/corrected with use of the amplitude offset feature.

--- End quote ---

I assumed that the spectrum analyzer internal attenuation is one of the tunable parameters of a spectrum analyzer, which should be adjusted by the User if necessary, and the external attanuators are intended to protect the spectrum analyzer from power overload (worst case destruction). Since in many cases you don't know exactly how high the signal level to be measured is (dynamic range of the signal), I assumed that you always have to attenuate a little more generously in order to protect the device.
tautech:

--- Quote from: fnaumann on February 09, 2024, 12:54:23 am ---
--- Quote from: tautech on February 09, 2024, 12:00:26 am ---Instead you should let the SA manage internal attenuation and add external attenuators when/if necessary.
External attenuation can then be nulled/corrected with use of the amplitude offset feature.

--- End quote ---

I assumed that the spectrum analyzer internal attenuation is one of the tunable parameters of a spectrum analyzer, which should be adjusted by the User if necessary, and the external attanuators are intended to protect the spectrum analyzer from power overload (worst case destruction). Since in many cases you don't know exactly how high the signal level to be measured is (dynamic range of the signal), I assumed that you always have to attenuate a little more generously in order to protect the device.

--- End quote ---
Certainly so depending on what you are doing however don't underestimate how sensitive a SA is, easily equivalent to any radio.
My first a SSA3032X, scared me regarding this sensitivity and how careless use could set the overload buzzer off so now the cellphone is never nearby when sensitivity is increased or the Preamp is on.
Later I got a SVA1015X and then upgraded to SVA1032X which remains my fav RF instrument where its SA capability is identical to SSA models.

In the early days I was terrified of front end damage yet now on my 3rd none have ever been damaged however anything that might offer a strong signal is first assessed with a simple non-contact RF loop.
Apart from those early days until I found my feet I no longer use external attenuators but have a small selection of N, SMA and BNC types should the need for them arise.
fnaumann:

--- Quote from: tautech on February 09, 2024, 01:26:10 am ---Certainly so depending on what you are doing however don't underestimate how sensitive a SA is, easily equivalent to any radio.

--- End quote ---
A measuring device that declares a max input level of 30 dBm and then issues an overload warning when the signal is -55 dB (E -5) weaker is suspect to me. And if a internal preamplifier activation in a menu can kill the device - such an option should not be able to be activated or should turn off by itself if it get critical. Surely that should be possible with such an expensive measuring device?

And let's assume that I'm too stupid to be able to display the signal sensibly on the SSA2021X , then the automatic function "Auto Tune" - offered in a separate button - should be able to display a measurement signal reasonably sensibly (signal-to-noise ratio) and not as a small bump surrounded by a sea of noise. And why is this all possible out of the box for a device that only costs a fraction?
tautech:
Some simple examples with 10dB attenuation on RF In using the default -20dB TG signal which of course will display ~-30dB sweep.



Then with an offset correction added and nothing else changed to now display a -20dB sweep....the TG level and with the 10dB attenuation corrected/nulled.



This is a simple and quick trick using the TG source to check you have set things correctly before proceeding to sniff anything of higher power.
When done this way Markers will display the correct amplitude values without any need for 'in the head' calculations.
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