Keeping my signals clear

kw: technical information, digital infrastructure

Are you ready for February's Digital Diversion? These days, it seems everyone has cable TV, to the tune of $50 monthly or so. Not me, I'm too cheap. I have an antenna in the attic, the largest one that would fit in the end room, with good cable between it and the set. The set has all the tuners needed to receive both digital and analog broadcasts and converts everything to a 1080i image. So I've been watching as much digital TV as the broadcasters have been making available.

In the suburbs some twenty miles southwest of Philadelphia, that's a lot, actually. I get five reasonably good analog signals and a handful of snowy messes. Digital? I get eight pretty solid signals and two spotty ones. Several of those channels have two or more feeds, so I can receive a total of sixteen to eighteen digital feeds, on a clear day (rain absorbs signal, and several drop out in bad weather).

I recently learned how to estimate the situation that is coming in February next year. Go to tvfool.com and enter your address. If you can, put the height of your antenna (If it is set-top 'rabbit ears', put zero). You'll get a nice graphic like the one below. Click on the image for a full-size GIF.


What does this show you? The radar circle on the left shows where to point an antenna for the strongest groups of signals in your area. Each circle is about a factor of ten weaker in strength. The colors give a good hint about what kind of antenna can receive a signal:

• Green = rabbit ears ought to be OK.
• Yellow = An attic antenna (like mine) can get these.
• Pink/Red = You need a roof-mounted antenna, the higher the better.
• Gray = Forget it, unless you can afford a really tall antenna tower plus a preamp.

I didn't show the gray ones on the screen clip here. It is for illustration anyway. I made this image for an antenna at 20 feet, about eight feet higher than the one I have now, to see how things would improve if I move the antenna I have to the top of the roof. It gained me a factor of five to ten in signal strength for the "fringier" signals, which ought to bring in several stations I don't get now. This is a great planning aid!

The list on the right is more detailed. The most important figure is NM(dB) under Signal. This is the Noise Margin, and needs to be greater than zero for your set to show you a picture. This needs to be adjusted; for example, typical preamps give you 10 or 20 dB more signal, while the wall of a house or the roof of an attic can absorb 5 to 10 (or more) dB. On the list I made with my real antenna height of 12 feet, I can estimate other losses. For example, I get channel 17.1, which has NM around 38, but not 12.1, at 26. I know I am losing about 10 dB in my roof, so there is at least another 16 dB loss in the system, probably from (1) the cable from antenna to set and (2) lots of trees in my yard. If I add a 20 dB preamp, it might pull in 12.1.

Going to roof mount, I find that these two channels have 57 dB and 47 dB, respectively, which is good news: about 20 more dB from height alone, plus I won't have the losses through the roof. Sounds like it is worth doing!

One other column worth noting is the Path under Signal:

• LOS = Line of Sight
• 1Edge = Diffracted once (adds 10 dB loss or more)
• 2Edge = Diffracted twice (adds 20-30 dB loss)
• Tropo = Scattered off the air in the troposphere. Basically well below the horizon!

Only the strongest broadcast signals can overcome the losses of the latter two categories. You'll note that in this image, all the Green signals are in the first two categories. Since I'm not yet pulling in all these, they're my target goal. If I manage to scrounge up any Pink ones in the bargain, that's gravy.

Virtual life with real consequences

kw: book reviews, science fiction, near-future, wearable computers, digital infrastructure

The title Rainbows End at first made me wonder if it simply embodied the recent trend toward eliminating apostropes. Then I figured it is a declarative sentence, to which I reply, "Yes, I suppose they do." Later in the book, the author makes the same pair of points, leaving his own reasoning obscure.

Halfway through the fourth chapter, I began to wonder if I'd read this before. I checked prior reviews and found that Chapter 4, titled "Synthetic Serendipity", had appeared in The Year's Best Science Fiction 2004, which I reviewed April 12, 2006.

Vernor Vinge throws ideas at you a bucket full at a time. The core plot is the struggle between a somewhat stereotypical mad medico who wishes to "save" the world—which requires enslaving it—and a global watchdog group, an extension of the Dept. of Homeland Security. This latter agency, still called DHS, wishes to prevent development of a technology called YGMB, for "you gotta believe me," a means of making your dictates simply irresistible.

The environment and setting provide the novel's allure. As near as I can figure, the central protagonist, Robert Gu, having been in high school in 1965—it is implied that was his senior year—is either my same age (60 later this year) or at most 2-3 years younger. At age 75, he places the time frame as 2022, or 2025 at the latest. There are allusions to seminal events "in the teens" that are recent memory to adults, but not to most youngsters, who'd have been too young to remember or not born yet.

Wearable computers have become clothing full of tiny processors and communications nodes linked to special contact lenses, which project images directly on the retina. The environment has become infrastructure, with every item bigger than a ladybug having its own digital tag. Thus, someone on a nature walk can call up a view of the landscape in which every bush, tree, and weed is tagged with botanical information, and taking a second look at any bug or other critter calls up appropriate zoological references.

People build their own world, so a row of suburban bungalows may appear as medieval huts to one, as "McMansions" to another, and hobbit-holes to someone else. People watching anything remotely can appear virtually, to anyone caring to see the virtual viewers. With a landscape full of cameras, you can see in any direction you want, including through the wall that happens to be in front of you (I'd find it hard to avoid walking into that wall, myself, at that point!), or from a treetop or spider burrow. Someone who is "wearing" can call up just about anything imaginable.

Call up how? Not with keystokes or mouse clicks. Your shirt and its sensors collaborate with you to build up a physical vocabulary of gestures and postures, in addition to subvocalized commands. When you've made yourself telepresent in a particular "space", things you say and do are heard and seen by others in that space. To communicate with a smaller audience one employs "sming" or silent messaging.

Highly acclaimed poet Robert Gu, aged 75, has the right genetics to respond almost miraculously to treatments that cure his Alzheimer's dementia and return most of his body to a 17-year-old's. His prostate seems to get stuck in his 50s, though, so he still has to get up a couple times nightly. He also finds that he has lost the ability to create poetry. Oh, he can spin words into rhyme well enough, rhymes that still affect others. But the sharp edge that made him a legend is gone. So is the sharp tongue with which he made himself sincerely hated by all who actually met him, family included.

The plot is complex, with several threads. A central thread is the efforts of the aforementioned medical scientist to keep his research secret. Another is the poet's desire to regain his poet's edge. His granddaughter hopes to help him leapfrog into the mid-21st Century by teaching him to "wear" (the word is never in quotes in the book. You just have to pick it up). He gets good enough to participate in what he thinks will be anti-establishment hijinks, but the plot is ever so much deeper than you can imagine, as he finds himself an unlikely savior of Civilization as We (might) Know It. A fun read.