The Invisible Hand is connected to the brain of the Pointy Haired Boss.
The whole Milton Friedman free market theory rests on the notion that people running corporations are competent, loyal, and are rewarded by getting money.
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com
The invisible hand moves in mysterious ways and slowly.
Next week there will be a glut of the things stuck on the shelves.
-- Regards, Martin Brown
I saw "screen rooms" like this when I worked at a moderately well-known consumer electronics manufacturer. I think the screen might have been copper but I'm not sure. The gaps between the wires were a little finer than your average household screen door, but not much. When there was a joint between two pieces of screen, IIRC they folded the edges over each other a couple of times and then used a staple or a screw. I don't remember how they got power and signal in, but Jeff's idea sounds right. I do remember that they would have braided ground straps to building ground. Light came from the normal fluorescents installed in the standard office drop ceiling. These weren't really meant to be disassembled - if they were empty, a couple of guys could probably move the complete structure to the other side of the room.
The screen room at ARRL HQ in Connecticut is in the basement. Also, you don't necessarily know what the staff does on the weekends...
Matt Roberds
The Invisible Hand is stealing them!
I'd put it down to either poorly-designed ordering software, or PHBs misusing said software. A relative of mine used to work for a large and well-known retailer. When she needed to reorder things for her department, the software would suggest quantities based on previous sales and projected demand. Over time, she found that the suggested amount was usually pretty close to right. It had trouble with very slow-moving items; if they sold none for a few weeks and then sold one, it would want to order two or three, and she learned to cut that down to zero or one, depending on the current stock.
Her boss had to sign off on the order after she got done. One of the bosses might occasionally say something like "This is a big quantity, did we really sell that many of those last week?", but would pretty much always approve it. A different boss would always go through and reduce the quantities on the order. This caused shelves to be empty for popular items.
Matt Roberds
Damn am I old.
The invisible hand only works for an efficient market. It can't handle incompetence, stupidity, nor laziness.
Sylvia.
Yes, that's right. Don't forget to include power and kleptocracy. The fed keeps throwing money into the stock market. (Chinese money, to be exact.)
They don't dare stop the inflation process, since they know that the house of cards will crash. We've been here before.
Donuts, anyone? :)
Ol Milt wasn't that dumb, not even close. He had no illusions about the results of crony capitalists. Have you driven a Russian car recently? :)
We drove through it two weeks ago, on the way to a gathering in Inverness. I supplied five pounds of Shrimp Remoulade; ever peel 5 pounds of medium shrimp?
It's beautiful up there, around Point Reyes.
====
I stay at a 10,000 acre reserve near there - unknown to the public. I'll send you an email, detailing how to get in, your option. This sounds like elitism, but it's actually not. jb
people running corporations are competent, loyal, and are rewarded by getting money.
In the book "The Price of Inequality" Joseph Stiglitiz recalls trying to persuade Milton Friedman that real human beings didn't conform to free market theory.
As far as Stiglitz could tell, Milton Friedman really was that dumb.
had been doing his thing for quite a while when Stiglitz tried to spell out Kahneman's data to Milton Friedman, and Friedman just didn't take it in.
-- Bill Sloman, Sydney
[snip]
Probably average around 10 pounds every New year's Eve... it's a family tradition :-) ...Jim Thompson
-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at
Jim I'm with you! I nice piece of yellow tail (tuna)
That sounds seriously cool. Thanks.
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation
Reality tends to be otherwise. There was a time when I found intermodulation at mountaintop radio sites on an almost daily basis.
Perhaps a simple demonstration would be useful. Take two RF signal generators. 2.4 GHz would be a good working area with each generator a few MHz different. Attach antennas to the generators and set them to belch as much RF as possible. Attach an antenna to a spectrum analyzer input and you should see two signals an no intermod products.
Now, throw a handfull of leaded RF diodes around the antennas and see what happens. Depending the length of leads (1/4 wavelength is idea), you should see quite a bit of IMD. You can also do it with a rusty bolt, although the effect is much less. That's what you'll have inside your screen room if it were made of galvanized chicken wire.
Incidentally, that's roughly the way PID (passive intermod distortion) is measured. Two 20 watt transmitters combined and a spectrum analyzer. Any non-linearity in the system, including dissimilar metals in connectors, will produce PID. A somewhat standard PID reference level is -115dBm.
At VHF/UHF/uwave, you can do about 20dB with absorbers than with sheet metal or mesh shields. Just build a box with the urethane foam boards around the lab. The catch is that it doesn't work well at low frequencies, where all the broadcast junk is probably hiding.
That begs the question of how well the circuit will work in the "real world" environment that might be RF polluted. You can't assume that the end user will have a pristine RF free environment. Drag your equipment to a crowded mountaintop site and see what it does. About half of my assorted DVM's don't work at all in an RF polluted environment.
The junk in the middle is TV, probably from Mt Sutro. The stuff to the left is probably FM broadcast and some commercial 2way stuff.
Ok... 3.6mv of rectified junk, probably from a mix of power line pickup and RF. My guess is that whatever it's seeing has some even harmonic content. If you feed your voltmeter a low distortion sine wave, there's no DC component so the meter doesn't show any DC. However, if it's full of even harmonics, it's asymmetrical about the
0v DC axis, and the voltmeter will show a DC offset.I presume you're measuring a +10.0v voltage source, which should be quite low impedance output. There must be a large amount of line junk or RF to produce even 3.6mv of DC across a low impedance load. I suggest you look for radiation from CCFL lamps, switching power supplies, wall warts, and fluorescent overhead lights. Also, try moving the two meters away from each other and other equipment. the switcher in my desk lamp wrecked a few measurements before I discovered that it was radiating RF junk. Although I presume your test leads are new, a crack in the insulation, with some leakage to your hand, might also produce an offset.
By CE, I assume you mean EMC (electro-magnetic compatibility). Yeah, looks like there might be a problem. However, the difference in readings between the two meters might be due to a difference in frequency response of the meters, making one less susceptible to power line junk. Is there an amplified output on the back of either meter that will let you see what it's measuring?
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Try Zatarains seafood boil and Arnaud's Remoulade sauce. Put a shrimp or two on a piece of crunchy lettuce, dab with sauce, roll up and eat.
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation
Brass turned out to be cheaper and more available than copper. Properties are similar to copper.
Yep, that's the stuff.
Yep, same method except just one fold per sheet edge forming a "hook". I wanted to use brass tacks to avoid dissimilar metals. I couldn't find brass staples. Do, I ran a strip of cardboard and stapled through the cardboard. There was still a dissimilar metal contact where the staple went through the cardboard and mesh, but at least it reduced the area involved. The strip of cardboard also served to hide the sloppy overlap at the seams.
Incidentally, be careful how you build the door. I forgot to account for thermal expansion. When the screen room was populated with test equipment, it became quite warm, causing the brass to expand slightly. That jammed the door shut. We got it open by brute force and later had to increase the gap (remove finger stock, Sawzall between joints, and beat on the frame with a small sledge hammer) to make the door work correctly.
Our shield room was sitting on carpet. We had a ground, but it wasn't for electrical purposes. It was because the carpet somehow built up a static charge and everyone was getting zapped when they touched the the insulated screen room. Conductive floor mats and some grounding eliminated that problem.
Yep. The lights were outside the screen room. There was a small desk lamp inside and a flashlight inside. The screening was dense enough to block much of the lighting, but it was adequate.
The company policy was to reorganize quarterly. The standard bad joke was "If my boss calls, get his name". I moved within the campus buildings twice in one year, and then to a facility in a nearby city (adding 30 mins to my commute each way). Moving is why the screen room had to be portable. The facilities people had become quite adept at moving offices and labs. I left my usual pile of papers and junk on my desk. After a weekend, I returned to find my desk and lab in a different building, but with everything on my desk and in the lab in exactly the same place as before. They photographed everything and put everything back as if nothing had happened.
However, the screen room didn't want to move. It was too big for the elevator. It also had a large plywood raised floor. It took a few days more, but they sectioned it with a saw, and screwed it back together much like the original. If I had to do it again, I would design and build it to be broken down and moved.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Years ago my dad helped with an outbreak of a mysterious disease in a group of German immigrants in San Antonio, TX.
The local guys had never seen it, but my dad spotted it right off-- trichinosis. The vicitms were making home-made pork sausage just like they'd always done back home--raw. They didn't know you can't do that here--we've got trichinosis, Europe doesn't.
Cheers, James Arthur
No, not really. It's more basic--whoever does "it" best does better, weeding out the less competent. It has worked amazingly well at optimizing all sorts of things.
The alternative theory, though, is that The People are incompetent and untrustworthy, so politicians(*) should run everything. (Preferably through a giant website--"it'll be like Travelocity"--and some snappy false-advertising.)
(*) Who are mostly lawyers, and famously trustworthy, selfless, competent, and reliable.
Cheers, James Arthur
I would guess that monel metal staples would have worked.
There are commercially available EMI filters for this.
Was the metal fabric grounded? Were those braided ground straps doing any good?
What I've done when fluorescent hash (SCR dimmer, magnetic ballast) is to use incandescent lamps and a variac, all outside the shielded space. A handle can come through the shield, so long as the shaft is grounded to the shield.
Especially at Halloween.
Joe Gwinn
That should work, assuming I can find some. (Nickel copper alloy). However, brass and brass plated staples are available today. For example:
Initially, no... which was the problem. The carpet made both a fine insulator and static electricity generator. Floating the screen room off of ground also didn't seem very electrically safe. I asked the company facilities people for permission to ground the screen room. After a few days of no answer, I just grabbed a few lengths of #14 awg solid wire, and did it myself.
What braided ground straps? If you mean the abominations used to ground motors that require vibration isolation, no way am I going to allow that junk anywhere near RF. The problem is that the individual strands of tin plated copper wire cross over each other in the braiding. A little vibration, and the individual strands will abrade off the tin plating. After the copper is exposed, electrolysis finishes the job by creating a mess of diodes. While it's nice having all that surface area to lower the ESR, braid is still an IMD generator. I use ordinary stranded copper wire for grounding. If I need more surface area, Litz wire, or do it myself Litz wire made from whatever insulated wire that I can find.
I was thinking of suggesting candles and kerosene lanterns for reducing EMI/RFI, but I was also sure that management did not want to deal with the fire insurance representatives.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
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