Hi Yves,
(and the rest of the group ;) )
?
Yesterday I soldered new resistors in the attenuator, it needed some tweaking to get the response flat but I finished it today.
I checked all the settings with a LiteVNA. The 10dB isn't perfect but close enough for now.?
| Att Setting |
300MHz |
600MHz |
900MHz |
1,2GHz |
1,5GHz |
1,8GHz |
| 10dB |
-10,5 |
-10,8 |
-11 |
-11 |
-10,7 |
-10 |
| 20dB |
-21 |
-21,2 |
-21,2 |
-21,3 |
-21,5 |
-21,6 |
| 30dB |
-30,8 |
-30,7 |
-30,4 |
-30,2 |
-30 |
-30 |
| 10+20 |
-30,6 |
-30,9 |
-31 |
-31 |
-30,6 |
-29,6 |
| 10+30 |
-40,5 |
-40,4 |
-40,2 |
-40 |
-39,2 |
-38 |
| 20+30 |
-50,9 |
-50,6 |
-50,4 |
-50 |
-49,8 |
-49,7 |
| 10+20+30 |
-60,7 |
-61,2 |
-61,5 |
-62 |
-62,1 |
-61,2 |
?
I build the attenuator back into the analyzer and checked the function.
The resulting levels are looking better, not perfect though. I'm expecting this will be fixed with new mixer diodes which should be in soon.
| Before Fix |
? |
? |
Now |
? |
|
?300MHz:
|
? |
?
|
?300MHz:
|
? |
|
Att
|
Level |
?
|
Att
|
Level |
|
10
|
-22 |
?
|
10
|
-15,7 |
|
20
|
-12 |
?
|
20
|
-16,3 |
|
30
|
-21 |
?
|
30
|
-17,3 |
|
40
|
-26 |
?
|
40
|
-18,7 |
|
50
|
-19 |
?
|
50
|
-20,9 |
|
60
|
-21 |
?
|
60
|
-21,8 |
?
I did a full self call which successfully passed and a confidence test which also passed.
The resulting Cal signal on screen though is still up at -5dBm instead of the expected -20dBm (I double checked the Cal output of the SA with another SA and it is around -20dBm. )
I'm starting to think there must be a problem with the calibration attenuator in A12, causing this level mismatch. Any experience with that? Or thoughts on how to verify it? Otherwise I guess i'm just going to take the A12 module out to have a look.
?
Marco
