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8722ES high band unlock after trace hold

Question asked by BobbyG_2016 on Nov 7, 2016
Latest reply on Nov 11, 2016 by BobbyG_2016

1) is it typical after powering on an 8722ES hitting sweep setup, running a single sweep, wait 5 minutes and then run continuous again and have the high band only go unlocked. It takes a few presets and then the 8722ES will re-lock. It'll say possible lock lost, and Phase lock lost. We came across this problem during verification tests using the 85057B. During verification test the trace is held until you hit continue. I paused during verification and the trace went off the screen because it was unlocked. 

2) I figured there may be an issue with Pretune values drifting during hold or possible high band mixer issues. In comparing an 8720ES to the 8722ES service test #43 I noticed difference not with frequency but with power. -22dB lower....... 

 

what should the output from port 1 be in regards to power? I know this is an adjustment for frequency but I'm concerned about the output from the A11.  In comparing a good 8720ES to the bad 8722ES and using a PSA I see the good unit has a PORT 1 power output of 9.5dB and the bad 8722ES has an output of -12dB. This is the first step of Pretune adjust so the signal are both approx 2.345GHz. Their frequencies are very close but the power difference is large. At 19.55GHz the 8722ES shows -14.5dB. The 8720ES does not have an adjustment for that step being a 20GHz NA. 

Any information on possible reasons other than pretune values that could cause a 8722ES to become unlocked after trace hold would be appreciated. I'm thinking a drift must be occurring as eventually the unit will phase lock again after say a 1 minute. Even preset will not re-lock it right away@. Thank you for the read -BobbyG  

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