Due to lightning within 60nm.
SO.......we spent the rest of the day going over our system, trying to figure out where the "missing" 20dB went from the other day when we tested it, and why the remote spectrum analyzer was acting all wacky.
We checked every connection (SMA and TNC) in the system, ruled out any network errors or timing problems, powered down/powered up, and rebooted everything, to no avail.
Finally, I decided to connect a different spectrum analyzer to the cable coming out of the switch matrix, on the off chance that the rack-mounted spec-a, just back from calibration, had a problem.
The Type-N connector soldered to the semirigid cable came off in my hand as I removed it from the input of the spec-a.
DOH!
Well, at least I found it........
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What I've Been Up To....
Started this post on Monday, then came down with a head cold, which is now progressing South. Feeling better, but still a bit woozy...... To...
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Man, I have half of a lifetime finding problems with metrology gear. Glad you found it, but there's no regaining time lost from shoddy gear maintenance.
ReplyDeleteLooking forward to the launch. Good luck!
Well, it wasn't shoddy maintenance that did us in, but rather the environment.
ReplyDeleteThis rack is located on the Launch Platform, all the way at the top by the helideck, and is built in a 20' shipping container. It's air-conditioned and dehumidified, but every time somebody open one of the doors, all that nice salt air comes in. It's also subject to a tremendous amount of shock, vibration, and acoustic noise, seeing as it's about 200 feet "slant range" from the pad.
A rocket with 2 MILLION pounds of thrust makes quite a racket as it lifts off! One of the mechanical engineers left a laptop running with a webcam on it during a launch a few years ago, and we all marveled at just how much things did the shake, rattle, and roll.
And we had a rather spectacular launch failure in 2007. Google for "NSS-8 failure" and you'll see what I mean.
All this equipment is the same that's been in the Comm Shack since about 2002 or so, and some of it is starting to show its (accelerated!) age. We had a National Instruments GPIB-to-Ethernet adapter that gave up the ghost a couple of weeks ago mounted in the rack, but other than having a couple of hard disks get scrambled, we've been remarkably fortunate.
*I* don't think they should have used UT141 semi-rigid ANYWHERE in the rack, but the guys that designed it thought it would be OK.
These are the same guys that spec'd ALUMINUM waveguide for the weather radar on the ACS, and we're still replacing bits and pieces of it as it fails from corrosion.