Yesterday was...disappointing. Exhausting.
I am not as young as I once was and even the small amount of physical work I did yesterday -- climbing ladders, carrying various heavy items, outdoors on a hot and humid day -- was a sharp reminder.
Sharper still was the discovery that at some time in the past, a large piece of falling ice (or perhaps an air-dropped bear) had struck the end of the feed assembly of the six-meter (call it twenty feet) satellite dish we were working on. It's a Cassegrain-feed antenna, built with the secondary reflector supported from the end of the feedhorn assembly by a truncated cone of RF-transparent plastic, with a heavy fiberglass cloth cover clamped over the thing to protected it from sunlight, weather and insects.
Heavy, opaque fiberglass cloth: there's no knowing what's underneath until you have trouble finding any satellite at all on a dish that should bring 'em in screaming-hot and go to find out why. And then when you give the dish another look-over, you notice the feed cover is a lot more wrinkled than it used to be.
The cover came apart when we tried to remove it. There was almost nothing left of the critical plastic piece underneath it. Any nicely RF-transparent plastic structurally rigid enough to support something like the secondary reflector is also a little brittle and forty years of seasonal temperature swings only makes it more so. The manual has no detailed drawings of it and the manufacturer was swallowed up by a large aerospace/defense contractor many years ago, which was in turn bought by an even larger (and more secretive) defense contractor and.... Well, good luck finding out if they still make or provide parts supports for their steerable Earth Station dishes. Over the phone, I couldn't even get them to admit there was such a thing as geostationary satellites.
And that was what I did yesterday. That and not picking up my new eyeglasses. Perhaps I'll be able to get them today.
BUILDING A 1:1 BALUN
4 years ago
7 comments:
OMG - Someone got 40 years out of that 6-meter dish setup? I am impressed!
This was a professional dish -- a massive kingpost design, with heavy-duty jackscrews of azimuth and elevation, driven by three-phase SEW Eurodrive severe duty motors. It will last as long as you can keep it painted and rust-free, the moving parts greased and the motors rebuilt.
This is similar, though larger.
We lost an 8.8m dish of similar design because I couldn't get my (then) bosses interested in having it scaled and painted. Wirebrush and rattlecan wasn't quite enough. It had some weak welds at the top of the upper kingpost braces that trapped water and rusted through. One stormy day, it went over.
Yikes! I'm happy I wasn't there to see the 8.8m dish go over. Having never messed with dish antennae, perhaps I am a bit cowardly. Mostly, what I've messed with are of the folded dipole type for 20, 40, 80 meters.
I hung a 20-meter one cattycorner across my apartment in college (think 1956) - suspended by tying the ends to curtain rods with narrow, black velvet ribbon (it was what I had on hand). My landlady had espied me in a tree, truncating my attempt to hang an outdoor antenna. Said landlady knocked on my door just before midnight, once, announcing, "Miss H..., your radar is cutting out my TV!" I turned on my transmitter to show her what real TVI would look like. ; )
"steerable Earth Station dishes" I wonder what Arthur C. Clarke would say.
And why, oh why, won't supervision-types listen the the techs who know WTH they're doing?!
Perhaps video of The Fall of Arecibo would be instructive. Every time operation changed hands legend has it that the upkeep budget was cut. Put it to them that Zen and the Art of Upkeep is woke for the sons and daughters of Martha. Or Something.
The blame -- if any -- should be ascribed to previous ownership and previous managers, who were themselves trapped in a long, ugly endgame of dwindling budgets and changing priorities.
The lack of a useful high-definition link from the North Campus to the main Skunk Workings meant the dishes had little to no value, and as more and more of our connections moved from satellites to terrestrial, IP-based systems, spending money on the big dishes made less and less short-term sense.
The new owners are more into "Disaster Recovery" prep; they are considerably larger but run at lower staffing levels, which means when something goes wrong, you can't just throw a room full of busy little techies like me at it and get it fixed by the end of that shift, because we no longer have that many busy little techies and their plates are already full. We need to have solutions already on the shelf, with minimum assembly required. That's brought some disused resources back into attention. It does give us access to shared resources, but we still need to be able to prop things up and keep them running with what we have on hand for a day or two.
Our North Campus also has a big Cassegrain feed dish, which regularly gets holes punched into the feed window from ice. Until we put together some spikes, squirrels would take up residence in the hub, making LNB replacement a hazmat affair. We are fortunate to have two HD TSL channels to use.
We still maintain 2GHz trucks, two-way radios and even have pieced together some leftovers to let us pass SMPTE310 through the 2GHz system for an emergency STL. Even have a number of copper POTS lines. We just might stay on the air if the WWW and the cell nets collapse.
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