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Comment: Re:It was never not prohibited (Score 2) 113

by Muad'Dave (#48926053) Attached to: FCC Prohibits Blocking of Personal Wi-Fi Hotspots

I understand Part 15 (as well as Part 97, since I'm licensed under those rules). The mechanisms mentioned in the GP _do_ exist in law for 5GHz U-NII (read WiFi) systems. Please refer to Title 47 Part 15, Subpart E, particularly 15.407(h)(1) and (2) and also 15.37(e).

Also, (if I read it correctly) 15.37(h) forbids the marketing or sale of devices that use any digital modulation technique other than Spread Spectrum operating in the 5725-5850 MHz bands starting on June 2, 2016.

The definition of "digital modulation" is distinct from SS - from 15.403(f):

(f) Digital modulation. The process by which the characteristics of a carrier wave are varied among a set of predetermined discrete values in accordance with a digital modulating function as specified in document ANSI C63.17-1998.

Comment: Re:It was never not prohibited (Score 2) 113

by Muad'Dave (#48922879) Attached to: FCC Prohibits Blocking of Personal Wi-Fi Hotspots

You're incorrect. Part 15 devices are absolutely required to not cause interference. From the link, emphasis mine:

(a) Persons operating intentional or unintentional radiators shall not be deemed to have any vested or recognizable right to continued use of any given frequency by virtue of prior registration or certification of equipment, or, for power line carrier systems, on the basis of prior notification of use pursuant to 90.35(g) of this chapter.
(b) Operation of an intentional, unintentional, or incidental radiator is subject to the conditions that no harmful interference is caused and that interference must be accepted that may be caused by the operation of an authorized radio station, by another intentional or unintentional radiator, by industrial, scientific and medical (ISM) equipment, or by an incidental radiator.
(c) The operator of a radio frequency device shall be required to cease operating the device upon notification by a Commission representative that the device is causing harmful interference. Operation shall not resume until the condition causing the harmful interference has been corrected.

Comment: Nice atmospheric window, but rainfade KILLS (Score 1) 54

I always post to the wrong duplicate article! ~sarcasm

From my other post:

According to line 'A' on this graph, the atmospheric absorption at 95-100 GHz is fairly low, but this graph shows that rainfade is an absolute killer. Light rain contributes 1 dB/km, which amounts to losing 20.6% of your signal per km. After 10km, you're under 1% of your original signal.

Somewhere between medium and heavy rain you cross the 10 dB/km line - you lose 90% of your signal per km. That ventures into 'unusable' territory very quickly.

Comment: Nice atmospheric window, but rainfade KILLS (Score 1) 1

by Muad'Dave (#48875183) Attached to: TWEETHER Project Promises 10Gbps mmW 92-95GHz Based Wireless Broadband

According to line 'A' on this graph, the atmospheric absorption at 95-100 GHz is fairly low, but this graph shows that rainfade is an absolute killer. Light rain contributes 1 dB/km, which amounts to losing 20.6% of your signal per km. After 10km, you're under 1% of your original signal.

Somewhere between medium and heavy rain you cross the 10 dB/km line - you lose 90% of your signal per km. That ventures into 'unusable' territory very quickly.

Comment: Re:Design failure (Score 1) 130

by Muad'Dave (#48866839) Attached to: Lost Beagle2 Probe Found 'Intact' On Mars

Why you link an article about hypothetical nano technology is bejond me :)

Because it's fascinating, and it mentions the extreme energy density of other 'safe' radionuclides besides Plutonium 238. That was the question that was asked in the parent post, after all. :-)

As for efficiency, I bet a closed-cycle Stirling Engine system could work on Mars with Gd148 as the heat source and a radiative heat sink to space or the (almost non-existent) Mars atmosphere as the sink. Naturally you could parallel the Gd148 sources so that no one source exceeded the max temp for the engine. If you're not willing to do that, there are other non-moving solutions that beat the paltry 3-7% of an RTG.

Comment: Re:Design failure (Score 1) 130

by Muad'Dave (#48848999) Attached to: Lost Beagle2 Probe Found 'Intact' On Mars

You assume RTG technology - I don't and I don't think the linked article does, either.

They discuss Energy Organs here, stating that (emphasis mine):

a sphere of Gd148 emitting ~100 watts with a 75-year half-life and measuring 3.41 cm in diameter with a 5-micron Pt shield glows at 1326 K (e-sub-r for Pt at 1326 K is 0.156; Gd melting point ~1585 K, Pt melting point ~2042 K); this is approximately the decomposition temperature of diamond (into graphite) and well above the combustion point for diamond in air (Section 6.5.3), so Pt-coated sapphire (sapphire melting point ~2310 K) may provide a more stable first wall for the radionuclide energy organ. Carnot thermal efficiency for a heat engine using this source could reach, at most, ~76%.

I'd say that's pretty good efficiency, and given the power levels and temperatures, I think non-RTG technologies should be used. If the system never drops below 0C, why not use a more conventional system?

Plus, you could just use the Gd148 to keep the craft warm and use other means to generate electrical power.

"The pyramid is opening!" "Which one?" "The one with the ever-widening hole in it!" -- The Firesign Theatre

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