开云体育

Hello,

I've got a tinySA Ultra in December 2022 and all was good (tests & calibration at least). I also have a tinySA non-ultra.
Yesterday while playing around, I've noticed that the signal level indicated by the Ultra is lower by about 10dB compared to the other.

I tried to do a self-test and level calibration and both failed (pictures attached).

I've cleared configuration and disabled "save config" in "presets" turned off and on (after a while as instructed by the seller) and measured the 30MHz CAL output signal which stays at ~-45dBm compared to the expected -35dBm. Measured the CAL signal with the other tinySA and it is around -35dBm so the output is good. Third picture is the CAL signal as measured by Ultra.
Is there anything else that can be done in terms of software/configuration or something is broken in hardware?
The system itself kinda works, but all signals are lower.

Do you have a scope?

If yes, can you input a 10MHz signal between -20dBm and 0dBm (such that it is well visible on your scope), you can use the tinySA to generate such a signal?
Remove carefully the cover close to the RF connector
Switch on the tinySA Ultra in default settings (0-800MHz) and measure the signal level at C58 and C24. (either side of the capacitor is OK)
The levels should be fairly close.
If not, the input switch is not working correctly
--

Hello, thank you for the response.

At 10MHz@-7dBm?output from tinySA, I get the following data:

- level indicated by Ultra: -17dBm
- input pin ~120mVpp
- C58 ~120mVpp
- C24 ~100mVpp

The input switch seems ok

Also measure either side of R44, close to the mixer
--

My mistake

It is 120mVpp at the entry point too, before anything else, so that is what the scope is measuring. I used that as a "reference".

If the input switch acts as a low impedance load the level measured at the input drops
Please measure the output level of the tinySA when set to -7dB.
This should be twice 280mVpp
--

TinySA @-7dB is ~780mVpp measured by the scope (high impedance, direct cable, 1X).
Same is 300mVpp with a 50ohm BNC terminator.
R44: ~80-90mVpp
C98: ~75-85mVpp

This confirms the input switch has too low impedance.
It is possible to replace the switch?
--

I don't even know what the switch is. I do have a hot air station and basic skills (THT).
Which part is the switch on the board?

Is it the part market A79? What kind o chip is this?

I think (I may be wrong, as a beginner) that the switch is for IN/OUT. If that is the case, I can replicate the 10dB error by doing the reverse: generate a signal with the Ultra and read it on tinySA. At [email protected],?tinySA reads -27dBm. Using the CAL output @10MHz I see -34dBm on tinySA.

You are almost correct
The switch is for the LNA but the signal path is bidirectional so if the switch is bad (e.g. creates 10dB loss) you will see this loss also when doing output
--

Yes. Its the input switch
See the FAQ??
Scroll down to "tinySA ULTRA questions"
--

OK, got this:?

I hope I'm able to replace it and this is the source of the problem.

A first test will be to remove the switch and check if the signal level at the input jumps up to the level without any load.
This will prove the ESD protection diode is not causing the problem
--

Removed it. 600mVpp vs 130mVpp before (10MHz@-7dB coming from tinySA).

Well, courier came with the parts today and replaced the RF switch (marked S79 instead of A79).
Everything is working again.

Thank you for the guidance, Erik!