Siglent SSA3021X Plus - TG missing 10 dB - Page 1
Forum section: electronics / testgear

author: arno
author_rank: Contributor
timestamp: March 01, 2020, 07:56:13 pm
content: Hello,I think I have a issue with my SA: When using the TG the display always shows 10 dB offset, so for example, the default value for the TG is -20 dBm, it reads -30 dBm.When using a very short cable to connect TG and RF Input the line is perfect flat. I received the unit in November and did a firmware update to the current version (2.2.1.2.5) on the day of arrival, means I can not tell if this issue was there before the update or not.I did not yet have the chance to measure TG out level or use a calibrated source to RF in.Thanks in advance!Update: I just connected the TG out to my scope. It shows a slightly distorted top on the sine.

author: tautech
author_rank: Super Contributor
timestamp: March 02, 2020, 08:10:14 am
content: Use Preset to set back to defaults and the TG level is corrected.This is a SVA1032X however the UI is very similar and shows default -20dB TG but not normalised.Normalisation is a little different for Plus and SVA models in that the sweep is stored first as a Reference trace and then normalised where corrections are applied to give a perfectly flat sweep. Further info on P39 of the users manual.TG levels can be set from -20 to 0dB.

author: hendorog
author_rank: Super Contributor
timestamp: March 02, 2020, 08:59:47 am
content: This might be something you have already tried, but suggest you do a factory reset - System | Power on/Preset | Factory Reset.Just to rule out any settings which you may have changed without realising, and also the possibility of the firmware upgrade doing something weird with the 'state' of the device.

author: arno
author_rank: Contributor
timestamp: March 02, 2020, 06:09:38 pm
content: Hi,thank you very much. I did a factory reset - did not help at all. The error remains. I think, I will have to send it back.Any other suggestions?Thank you so much!

author: tautech
author_rank: Super Contributor
timestamp: March 02, 2020, 07:21:58 pm
content: Quote from: arno on March 02, 2020, 06:09:38 pmOK, so if you look at my screenshot, is your TG Offset set to 0dB ?Could you post a screenshot please.

author: arno
author_rank: Contributor
timestamp: March 02, 2020, 08:10:26 pm
content: Here you are!

author: tautech
author_rank: Super Contributor
timestamp: March 02, 2020, 08:23:41 pm
content: Quote from: arno on March 02, 2020, 08:10:26 pmOK good thank you.Please check 2 more things.Check your cable is 0 ohms.Reinstall the firmware.

author: arno
author_rank: Contributor
timestamp: March 02, 2020, 08:34:24 pm
content: Hi,checked with different cables, including a short patch with Highflexx 7. Reinstalled the firmware already yesterday. Makes no difference.Thank you for your help!

author: tautech
author_rank: Super Contributor
timestamp: March 02, 2020, 08:42:21 pm
content: Quote from: arno on March 02, 2020, 08:34:24 pmOK, good.Check System menu and Preset settings to ensure Preset returns to full factory defaults.

author: arno
author_rank: Contributor
timestamp: March 02, 2020, 08:49:04 pm
content: Checked, all 'good'. Still 10 dB below.

author: tautech
author_rank: Super Contributor
timestamp: March 02, 2020, 08:57:26 pm
content: Quote from: arno on March 02, 2020, 08:49:04 pmI'll link factory tech support to this problem but I won't have a reply for some hours until later today.I don't have the exact same model in stock again for another couple of weeks so I can't attempt to replicate this issue except with SVA's, sorry.The factory will check for us.

author: arno
author_rank: Contributor
timestamp: March 02, 2020, 09:04:22 pm
content: That's allright, I will be out of office/home until Friday

author: tautech
author_rank: Super Contributor
timestamp: March 03, 2020, 01:58:44 am
content: Quote from: arno on March 02, 2020, 09:04:22 pmSiglent tech support request you to use another signal source to confirm where the 10dB level error is.This way we can tell if the TG level is the problem or if it is the RF input.Do you have another instrument that can provide a reasonably accurate sine wave level ?It does not need to be very high frequency, a few 10's of MHz is OK.

author: arno
author_rank: Contributor
timestamp: March 03, 2020, 09:38:43 am
content: Hi,I set the frequency span to 1 - 2 MHz, small bandwidth. Attached the plot on my scope with TG levels set to -20 dBm and 0dBm. Input coupling set to 50 Ohms.Thanks!

author: tubularnut
author_rank: Regular Contributor
timestamp: March 03, 2020, 07:54:24 pm
content: This may not help at all, but only to show the response on my Plus is just about on -20dBm (with a cheap 50ohm co-ax)Also my TG shows the slight flat top for 1MHz at 0dBm as in the OP image. (50ohm terminator on scope)

author: arno
author_rank: Contributor
timestamp: March 03, 2020, 09:18:12 pm
content: Interesting! Both signals look the same to me (except for the amber glow on my screen) So I expect the TG Out of my SSA to be fine.

author: tautech
author_rank: Super Contributor
timestamp: March 04, 2020, 09:10:27 am
content: Quote from: arno on March 03, 2020, 09:18:12 pmYes, that's my interpretation too. Thanks tubularnut.I won't have SSA Plus stock for a few weeks so can't do any checking my end however with tubularnut's info that leaves us with a possible -10dB error on the RF input so we wait for advice from Siglent for your next course of action.@arno, my sources tell me you are in contact with Siglent, great and they will fix you up.Report back on the outcome when resolved.

author: arno
author_rank: Contributor
timestamp: April 23, 2020, 10:14:18 am
content: Hello again,the analyzer finally arrived back here from Siglent with the issue fixed. Unfortunately I haven't got any description, yet.Thanks again to all!73 de Arno, DL2SSB