Products > Test Equipment
DSA875, damaged?
grg183:
HI,
I have a DSA875 which got accidentally fed a +26dBm signal at 2.5GHz. The DSA was setup with 30dB internal attenuation but unfortunately no external attenuator and by the time I realized it had already been running on this signal for a while. I don't recall seeing any overload warnings from the DSA but the max hold plot was saturated on the +20dBm mark so I thought it was on the limit but still safe (I should have added an external attenuator, I know). After a while of this, I started reading a lower signal. The frequency and shape of the signal were correct but the amplitude went down to 0dBm (for the same signal as before).
I don't have a way to test with a separate signal generator or second analyzer at the moment so to test it out I connected the TG from the same DSA directly to its input expecting to see a flat plot. The attached screenshot is what I got with the TG set on -10dBm full span. Below around 3.2GHz, there is roughly a -25dB attenuation but above 3.2GHz it seems to be measuring correctly. I loaded the system preset before doing this measurement.
It is interesting that below 3.2GHz it seems to still be measuring but with an attenuated reading.
Am I missing something or is it damaged? Anyone had this happen?
tv84:
Have you tried a settings reset?
tautech:
--- Quote from: tv84 on June 20, 2023, 09:38:45 am ---Have you tried a settings reset?
--- End quote ---
--- Quote from: grg183 on June 20, 2023, 02:52:02 am ---I loaded the system preset before doing this measurement.
--- End quote ---
It seems so.
FWIW I've seen the same stepped sweep at 600 MHz in a Siglent unit that has also been damaged.
If the TG wasn't in use at the time it's likely okay and just the RF input damaged.
RFDx:
--- Quote from: grg183 on June 20, 2023, 02:52:02 am ---It is interesting that below 3.2GHz it seems to still be measuring but with an attenuated reading.
Am I missing something or is it damaged? Anyone had this happen?
--- End quote ---
It looks like the SA is using two receiver frontends to cover the full 7.5GHz span. Something happened to the frontend responsible for the 3.2GHz range. The strange thing is that the TG plot is flat up to 3.2GHz. It doesn't seem like something got damaged just permanently attenuated by about 26dB.
grg183:
--- Quote from: RFDx on June 20, 2023, 11:42:57 am ---It looks like the SA is using two receiver frontends to cover the full 7.5GHz span. Something happened to the frontend responsible for the 3.2GHz range. The strange thing is that the TG plot is flat up to 3.2GHz. It doesn't seem like something got damaged just permanently attenuated by about 26dB.
--- End quote ---
Yes that's what I thought too, they must have 2 receivers, one for <3.2GHz, and another for >3.2Ghz, which probably makes sense considering there is another model in the DSA800 series limited to 3.2GHz.
--- Quote from: tautech on June 20, 2023, 09:45:15 am ---FWIW I've seen the same stepped sweep at 600 MHz in a Siglent unit that has also been damaged.
If the TG wasn't in use at the time it's likely okay and just the RF input damaged.
--- End quote ---
The TG itself should be fine, I've barely ever used it and it was not in use at the time. At the time of the damage I had it set on 2.508GHz with 10MHz span, 30dB internal attenuator, 20dBm reference level and the signal was displayed top flattened on the 20dBm mark, later I found the connected device was outputting around 26dBm.
It seem like something in the measurement path got degraded resulting in an attenuation but the receiver itself seem to still be good. I've tried a few known signals and they are displayed perfectly just attenuated.
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