Any luck on finding out the reason for the band errors?
http://www.bymm.de/documents/35/FSEM_V1_16.pdf
Most easy way would be to alter the tables if you pull out the HDD and directly edit the files
I did not have much time to play with it this week. Prepping up the basement to install a new furnace and hot water heater before the cold season arrives. And, boy, do I have lots of junk and stuff to move around to get the furnace in...
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Read the FSEM_V1_16.pdf.
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This is very nicely done and you are right the calibration strategy will likely be similar. Thanks for the link. It also helped to spruce up my high school German too
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I guess learning a language young is like riding a bike: it comes back even if you have not used it in a long while.
I did have time to do a few things before removing my workbench however.
First:
I removed the Tx cable and put the RxTx module Tx output in the HP8561 SA and calibrated the SA levels in dBm.
Then I requested the CMU200 to use the RFout2 out on the RF frontend (even though it is disconnected from the TxRx module).
I asked the CMU200 to go to 1430MHz (frequency with worst self-test error) and systematically changed the levels from 0 dBm to -90 dBm in -10 dBm increments.
The TxRx module output did not follow the requested step sizes. It went down in steps of -10 then -20, another -20 and finally -10 db.
![Confused :-//](https://www.eevblog.com/forum/Smileys/default/confused0024.gif.pagespeed.ce.5xOqKkq0Co.gif)
I then requested the CMU200 to use RF1 out. Same setup, RF front end not connected to the TxRx module.
I got steps of 20db, 10dB, 10 dB, 20dB between the levels.
I then requested the RF3out and got steps of 10, 10, 15, 10, 10, 20 between the -10dBm levels requested.
Again, a different pattern.
Since these are different patterns for the same level requests it means the TxRx module is told to compensate differently according to the various losses/gain expected in the RF frontend module path to the front panel outputs.... Also, since the RF frontend is not getting any RF, if there is a feedback loop or AGC implemented it will go nuts and that might be the cause of this behaviour.
Next I did the same using RF4in, RF2in and RF1in using the RFfront end connected to the TxRx module normally with a HP8648 signal generator at 1430MHz. The CMU200 power and SA readings were all OK on the CMU200 display. So now I assume the receive chain portion of the CMU200 is most likely OK and that all my issues are indeed on the RF generation side. (I could be wrong still
![Broken! :-BROKE](https://www.eevblog.com/forum/Smileys/default/smiliey_scope_broke.gif)
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I now have to redo this feeding RF to the RF front end and see if the output is varied in a complementary fashion to the TxRx module output.
Really looks like there is an interplay between the DSP, TxRx module and RF frontend module depending on levels and paths requested. Not a surprise, considering the matrix of RF switches and amplifiers on each. Also since a do not get precise 10, 20 etc dB variations at each step there might also be correction values applied in each module that are specific to each freq/dBm combo
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Final run before gutting my workshop bench.
Since these measurement would take a long time to do by hand I downloaded FreRes from R&S and set it up to scan from 50 to 2500MHz.
I reconnected the TxRx module to the RF frontend module correctly and did scans at "requested" 0dBm, -20dBm, -40dBm, -60dBm and -80dBm for both RF3out into RF2in and also for RF2out into RF2in.
Just to see a better picture than the selftest was providing.
Interesting:
for RF3out/RF2in the response is fairly flat for 0, -20 and -60dBm. There is a switching step around 2.2GHz visible in all traces in addition to the deviation around 1.5GHz for -40 and -80 dBm.....
for RFout2/RFin2... well yikes
![Scared :scared:](https://www.eevblog.com/forum/Smileys/default/scared.gif.pagespeed.ce.oZptHNcbsD.gif)
Did not do other runs yet but it looks like there are possibly many players here between all three modules and how they are implementing the RF chain ....
My next step will be to input RF from my freq gen in the RF frontend in place of the TxRx output and see how the three RFout behave and if it is related to the gain variation seen at the TxRx module output..
I also need to understand better the architecture before trying to modify files in the OS. FSEM_V1_16.pdf is great to help here
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