The main thing is the ease of getting huge intercepted areas with a single pair of wires (i.e. one port), and a contributing thing is the energy per photon.
The etendue (area*solid angle product) of a single electromagnetic mode is
E = lambda**2 / 2.
If you need more etendue than that, i.e. either a wider acceptance angle or more intercepted area, you have to use either multiple ports or incoherent detection. The SNR tradeoff involved in going to much shorter wavelength is fairly heartbreaking.
** Why is no-one here considering the safety issue of NO usable RF inside one's home ? For a great many, that is not just inconvenient it is positively DANGEROUS.
The use of mobiles ( ie cell phones ) has taken over from old wired phones using twisted pair and with modern broadband connections. The ability to make emergency calls from within one's home is ESSENTIAL.
Faraday shielding residential properties needs to be made illegal. ==================================================
Exactly. We're not concerned with heat "leaking out" (like you'd be in northern climates) but, rather, leaking *in*. There's a different kind of coating (process) prefered -- "soft coat" -- that deposits a couple of fine layers of silver on the glass using magnetron sputtering vapor deposition. "Hard coat" is fused with the glass during its transition from liquid to "solid".
And, windows only allow "radiation" in that is "directed" inward (hence the reason sunlight is shaded out by "wide" overhangs).
Apparently it's much more effective (and comfortable) to step outside to talk than to stand in front of the window (?)...
On Friday, 6 May 2022 at 10:28:07 UTC-7, Don Y wrote: ...
Most phones and carriers these days support WiFi Calling where phone calls and SMS messages are routed over the internet as an alternate to wireless. The phone will (fairly) seamlessly switch between using WiFi and cellular radio as the relative signal strengths change or wifi service is available.
The carriers still charge for time, even if they are using your own wifi.
I have to assume that they either don't use this feature, don't know *how* to use this feature *or* that it is unreliable, as well (?)
Speaking with a colleague two days ago and the call was dropped twice over the course of 30 minutes. I'm talking on copper wire so I doubt it's on my end!
It seems that people now EXPECT calls to be unreliable whereas that was far from the case with older technology (batteries dying, dead spots, etc.)
I'll be doing a VoIP port, soon, so I'll see what quirks *that* has.
Although it does and mine are low emissivity there seems to be very little attenuation at any of FM, DAB, Wifi or mobile phone frequencies. I guess it is thin enough that most wavelengths are unaffected.
The stuff we had on the computer room windows for radio telescope control had woven copper mesh inside grounded at every edge and an airlock of two doors with all the fittings between the computer suite and the outside world. Its attenuation was good up to 32GHz which was as high as we could go. Door seals caused trouble from time to time.
The computer sitting in the innermost really good windowless Faraday cage to protect IF stages and correlators from its interference. That was a cost no object lined with 1/16" copper sheet - it looked fabulous! (shame that the door was normally kept shut so no-one got to see it)
It is only really a problem in the US where short tons are used to defraud the buyer of 10% of what they paid for. An Imperial or British ton and a metric Ton are close enough for most practical purposes.
US short measure sharp practice gets you problems like the Gimli glider.
The three types are all a measure of mass(weight) the short ton aka US ton is 2,000/lbs. the long ton aka British ton is 2240 lbs. the third ton is the metric ton which is, equal to 1000 kilograms, or approximately 2204 pounds.
What is a short ton vs ton?
United States. In the United States, a short ton is usually known simply as a "ton", without distinguishing it from the tonne (1,000 kilograms or
2,204.62262 pounds), known there as the "metric ton", or the long ton also known as the "imperial ton" (2,240 pounds or 1,016.0469088 kilograms).
Why is it called a short ton?
In the U.S. there are 100 pounds in the hundredweight, and in Britain there are 112 pounds in the hundredweight. This causes the actual weight of the ton to differ between countries. To distinguish between the two tons, the smaller U.S. ton is called short, while the larger British ton is called long.
What is the meaning of hundredweight?
A hundredweight (abbreviated as CWT) is a standard unit of weight or mass used in certain commodities markets. It also may be used to price smaller shipments of goods. In North America, a hundredweight is equal to 100 pounds; in the United Kingdom, a hundredweight is 112 pounds.
Why is it called a hundredweight?
In England in around 1300, different "hundreds" (centum in Medieval Latin) were defined. The Weights and Measures Act 1835 formally established the present imperial hundredweight of 112 lb. The United States and Canada came to use the term "hundredweight" to refer to a unit of 100 lb.
What is the difference between a long and short ton?
ton, unit of weight in the avoirdupois system equal to 2,000 pounds (907.18 kg) in the United States (the short ton) and 2,240 pounds (1,016.05 kg) in Britain (the long ton). The metric ton used in most other countries is
1,000 kg, equivalent to 2,204.6 pounds avoirdupois.
What is the British ton?
"The ton" was Britain's high society during the late Regency and the reign of George IV, and later. The word means, in this context, "manners" or "style" and is pronounced as in French.
A ton is defined as 20 hundredweights but a British hundredweight is 112 pounds for some obscure reason going back to stones, another strange unit of measurement. Why there are 8 stones in a hundredweight also escapes me. Actually Canada uses short tons.
They did use the imperial gallon so I always thought I was getting a bargain when buying gasoline in Canada. After going to the liter and the loonie (Canadian dollar) falling to .75 USD, I gave up trying to figure out how badly I was getting screwed. The US uses the Queen Anne's gallon and wasn't about to adopt the Imperial system in 1826. We also retained the Winchester bushel. I can't find a citation but it wouldn't surprise me if a hundredweight was 100 pounds before 1826 too.
Anyway the Gimli Glider was the end result of many more problems than a simple conversion. It wasn't a high point for Air Canada. Boeing certainly didn't help. I once worked for a firm that did fuel measurement and management systems. We didn't assume the engines would be running to keep the system powered up. Admittedly the systems primarily went into military aircraft where a little wear and tear is expected, but still...
I'll drink to that... I have two US vehicles, a F150 pickup and a Harley bike. Both are mostly SAE (inch) fasteners, except when they aren't so I need wrenches in both sizes. I believe newer vehicles are all metric. With the Toyota and two Suzuki bikes I know they'll be metric. Thankfully I haven't had to deal with Whitworth in decades.
The US has been talking about metrication for decades but the legislation has only been a suggestion not a mandate. The only wholehearted adopters were the liquor bottlers. A 'fifth' (of a gallon) was a customary size and was 757ml. Seems trivial to go to 750ml but those milliliters add up.
In an era where a 5lb sack of sugar becomes 4lbs in hopes nobody notices, I really don't think a short ton was meant to defraud. Before Canada went metric everyone (except the completely clueless) knew what you were getting on either side of the border when you bought a gallon of gasoline.
Yes, briefly. That was my first and last brush with DoD projects. It didn't help that it was in the middle of the walker debacle and DISCO put everything on hold as far as clearances went. I'd been hired to work on the test kit software but when there's nothing to test...
The upside was I had plenty of spare time to go down to Middlebury and learn how to fly. The FBO was run by an ag pilot whose family had originally built the strip for their spraying operation. It was interesting to say the least. He had a couple of elderly Larks, one of which added pumping up the brakes to the usual final approach protocol.
I was moonlighting for another employee who had a side project going. He contacted me almost a year later about some tax paperwork. I asked if he'd written any code yet. The answer was no, they were still haggling over the design document. I can fully understand why projects like the F-35 have problems.
I'd taken a contract at GE Ft. Wayne to develop a copier power supply testing system and it was very refreshing to actually make progress.
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