AnsweredAssumed Answered

E4436B Strange Problem

Question asked by swperk on Jun 25, 2010
Latest reply on Feb 27, 2017 by jlubecky
I just acquired an E4436B with options UND, 100, and H99. The seller described it as "gets bad signals" but could not provide any further details. When it arrived, it looked to have been well taken care of, with a cal tag from 2006. I powered it up and noticed that the display had a series of dark vertical segments like a picket fence, but otherwise the unit seemed to operate normally. When I removed the front panel to investigate the display, I found a partially inserted ribbon cable from the display to the motherboard. Reinserting it fixed the display problem, but that, and other findings  like a loose SMA connector on the output connector, a missing screw, and a loose cable clamp indicated that someone had been inside it before.

At first, all I noticed that seemed wrong with the output was that it was down about 0.5 dB, and didn't consider that a serious problem. However, when  I started looking at various frequencies on my E4402B, I found that at exactly 2 GHz the phase noise was so severe that the peak couldn't be seen very well at all, and the phase noise spread for several MHz on either side of the carrier. Here's the part I think is weird: When I adjusted the output from 2.000 000 000 00 GHz to 2.000 000 000 01 GHz (up by 0.01 Hz) the phase noise went away completely and the signal looked perfect. Also, when I tuned to less than 1.990 GHz, the signal looked fine. I haven't investigated all of the other ranges yet. In the range between 2.000 GHz and 1.990 GHz, the phase noise decreased with decreasing frequency, and what I saw on my SA was randomly occurring brief, discrete spikes for several MHz on either side of the carrier, becoming less frequent and less apparent as the frequency was decreased.

I have essentially no troubleshooting experience with the ESG series, so I'd appreciate any suggestions.