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span setting affects marker pos when measuring CW test signal on E4448A ?

Question asked by marlboroman77 on Apr 20, 2012
Latest reply on Apr 24, 2012 by tabbott
  • Comment • 1
Hi,

I am performing the following test on E4448A

Objective: measure a CW  test signal at 14GHz with various span settings and with RBW set to 3.9KHz

Test Steps:
1. set centre frequency to 14.906 GHz, span  1MHz
2. detector RMS, RBW=3.9 KHz sweep time such that uncal does not appear on screen
3. set test signal (generator) level to  -10 dBm @ 14.906 GHz, wait for complete sweep
4. press "marker"--> peak search
5. record marker position (y axis)  obtained in step 4
6. repeat steps 1-5 with spans 5MHz, 12.5MHz,  20MHz, ,25MHz, 50MHz, 100MHz, and increase sweep time such that uncal does not appear on screen (40 Sec)

Expected Result:
marker position does not depend on span

Actual Result:

I got the following table, as you can see, the marker position seemed to be related to what span I used

RBW=3.9KHz
SPAN     Marker1 Position
1MHz       -13.64 dBm
5MHz       -16.37 dBm
12.5MHz   -20.28 dBm
20MHz      -22.32 dBm
25MHz      -23.28 dBm
50MHz      -26 dBm
100MHz    -29 dBm

why did the marker peak move when I changed the span ?

thanks
Joe  
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