Atomic I/O letters column #70
Originally published in Atomic: Maximum Power Computing Last modified 16-Jan-2015.Hold the antenna, stand on one leg, wave your other arm...
I live in a rather large house in which the wireless network signal has to pass through a fair few walls that create some small dead spots in the house.
I have been browsing around and noticed that there were three solutions available that may or may not solve my problem.
First was the wireless range extender offered by D-Link, which I believe simply acts as a repeater. The second solution was replacing the antenna on the wireless router with a 5dB or 7dB version offered by D-Link. Finally, I came across the Netcomm indoor wireless booster (200 or 500 mW versions) which gets attached between the router and the antenna.
I was just wondering which of these would offer the best solution to extend my wireless network, or if there are any better solutions available?
Tony
Answer:
Provided you've already got your wireless access point sitting somewhere high up and near the middle of the house,
a bigger antenna will probably do the job.
Power boosters are all very well, but they don't increase an access point's receive sensitivity. A high power transmitter may be detectable for miles around, but that's no use if it can't hear return signals. A simple antenna upgrade, in contrast, increases signal level and receive sensitivity simultaneously.
The standard antennas on access points generally only have around 3dB of gain, which combined with the miserable gain of the antennas built into many laptops and WiFi cards can, indeed, be bad news.
But you can get 9dB omnidirectional SMA-connector antennas (technically it's a reverse polarity, or "RP", SMA connector) on eBay these days for maybe $US15 delivered (see the ones mentioned in this Tech Zone piece, for instance).
Each 3dB is a doubling of power (which sounds as if it should be impossible, and kind of is), so upgrading from stock 3dB to a 9dB antenna should give you around four times the signal level at any given point. The big no-name antennas are also far cheaper than brand-name smaller ones.
If you've got an access point/router with a standard RP-SMA connector for its antenna(s), the upgrade is dead simple. Remove old antenna, plug in new one. The access point probably won't even care if you do this while it's on, but it's polite to turn it off first.
(If your access point doesn't have external SMA antenna sockets, by the way, then it may have an MC Card or other mini-connector, and that connector may be inconveniently located inside the casing.)
Make sure that you buy an omnidirectional antenna, not a directional one. Directional antennas have much better gain figures than similar-sized omnis, but that gain only applies in the one direction the antenna is pointing. Directional antennas can be used on network access points - if you've got an AP with two antennas then you can probably replace one antenna with a directional unit pointing in whatever direction's most important to you - but you probably want an omni.
Note that it's also not very difficult to make your own 6dB or better antenna. The only special part you need is a plug to suit the socket on your access point.
Perhaps there's a hidden hot tub
According to the specs of Dell's 30" LCD, it has a power consumption of up to 147 watts. That's more than my 21" CRT! There goes my idea of boosting my UPS run time by switching to an LCD.
I thought LCDs were supposed to be low power? Surely they don't stick a 140 watt backlight in them?
Adam
Answer:
Yes, large LCDs can consume a surprising amount of power. But they often don't, and there are some other factors to
consider.
First up: The power ratings on the back of appliances are usually higher than what the device actually typically draws. This is so that people don't get taken by surprise by the inrush current as their CRT degausses, or by the hefty draw of their laser printer or refrigerator when it's warming its fuser or running its compressor, respectively. It's good practice to set up your wiring as if you expected everything to draw its rated power all the time, but only things like heaters, toasters and light bulbs actually do.
Secondly: A 30 inch 16:9-aspect-ratio LCD has almost exactly twice as much screen area as a "21 inch" 4:3 CRT with a 20 inch viewable diagonal. That's a whole lot of monitor, and it all needs power to switch and light its pixels.
It's not hard to find 20 inch LCDs with maximum power ratings down around 75 watts. That's about the same rating as a modern "17 inch" CRT - viewable diagonal 16 inches, with about two thirds of the screen area of the genuine 20 inch LCD.
Thirdly: Modern LCDs generally have very high maximum brightness. Unless you're using them somewhere brightly lit, you can and should run them at nothing like their maximum brightness. That'll save some watts, as well as your eyesight. One of the most basic ergonomic mistakes is running your monitor too bright - it shouldn't actually be any brighter than a well-lit book.
Fourthly: LCDs are much better suited to power-saving blanking than CRTs. A CRT in sleep mode has to warm up when it's turned back on, but an LCD can turn on almost as fast as a light bulb. This makes it much more practical to set a short monitor-sleep delay, which saves even more power.
(I've measured the power consumption of a Dell 3007WFP-HC, now. Read all about it here!)
Rising smoke also a concern
What should a Peltier read on an ohmmeter? My little fridge has packed up and it's either the Peltier or its the switchmode PSU. The PSU is fine under mild load (i.e. the fridge fan), and off load. The Peltier on my meter reads zero ohms, both ways. I think not good for a semiconductor device?
Martin
Answer:
I don't know the impedance range for different Peltiers, but there should be some kind of reading in one direction,
as the small current the meter delivers passes through the device. If the Peltier reads zero both ways then it's shorted
out, which is indeed bad; if it reads infinity (or whatever the meter's maximum is) ohms either way then it's open-circuit,
which is approximately just as bad. There's not much you can do about either problem - in theory it's possible to
pry a Peltier device apart and bypass the dead junction(s), but in practice it's just not going to happen.
Peltiers most often die, I think, because water gets into them. This can obviously happen easily when there's condensation on or around the element - they're sealed around the edges to keep it out, but the sealing on the cheap Peltiers used in mini-fridges probably isn't very good, and the ones people use in PC water cooling rigs often aren't much better.
If it falls off, it isn't necessary
I was recently installing my brand new XFX GeForce 7950 GT and, in a move of pure brilliance, managed to break a piece off. It's one of those little cylinder things that sticks out of the card, looks a bit like a battery. It's maybe 5mm across and about the same high. On it, it says "50, 100, 25a". The card seems to work just fine, but I'm concerned I'll have problems down the road. Any idea what it might be?
Tom
Answer:
It's an electrolytic capacitor, probably for power
supply smoothing.
Your video card is, therefore, probably now a bit more susceptible to misbehaviour if it gets noisy power from your motherboard. In practice, this is unlikely to ever be a problem.
But don't do it again.
Incidentally, the smoothing caps that you usually find in a forest around CPU sockets are similarly semi-disposable. It's not good if you break one or two of them off, but as long as you don't manage to create a short circuit out of what's left, the computer will usually keep on running just fine.
This is just as well, by the way, because these large capacitors are all of the electrolytic type (a.k.a. "electros"), too. They're the only capacitor type that gives you large capacitance values in a small-ish space for a low price, but they're famous for drying out over time and changing value. If you make something that depends for its operation on an electrolytic capacitor holding its value, then that device will be certain to drop dead after a few years. But as things stand, old computers just get touchier about their power supply.
(Old power supplies are dodgier, too - they've got quite large electros in them.)
The Mystery Cable
I am planning to hook my game console up to a computer monitor and a simple set of speakers with standard input. I wanted to use the console's component video, and I was able to find a component-to-VGA adapter for the monitor.
The left and right audio have been a little trickier. Nobody seems to have what I need in that area - two RCA sockets on one end, one computer-style 1/8th inch stereo socket on the other.
I was wondering If you could point me towards a retailer that carries something along these I have tried searching "the Google" to no avail.
I also have found similar cords with both male and female connectors that I could use with a few other adapters, but I don't want to have to buy multiple parts and daisy chain them if it is not necessary to do so.
Adam
That ought to do it.
Answer:
The opposite gender adapter to the one you want - two RCA plugs to a stereo 1/8th inch
jack plug - is a standard cable that people use to hook
a PC up to a regular hi-fi system. You can get them from any electronics store;
here's an unnecessarily fancy one.
Worst case scenario, as you say, you could get one of those, one 1/8th inch stereo female-to-female adapter, and two RCA female-to-female adapters, and you'd be set. Those latter adapters (or "couplers") are small solid objects, not cables; this sort of thing. They're standard electronics-store items, too.
The extra couplers certainly aren't an optimal solution, but they'll get the job done well enough for audio.
I've never seen the female-to-female version of the cable as a separate item. I think I saw one as part of the bundle for a speaker set, or something, once.
You may have more luck if you look for one that has the female RCA sockets you want and a male 1/8th inch plug, so you'd only need one coupler, but I couldn't find anybody that had one of those in Australia, either.
(Radio Shack in the States has this one. Or had, anyway; it doesn't seem to be there any more.)
Of course, anybody remotely handy with a soldering iron could knock up the cable you want in ten minutes. Every half-decent electronics store has the parts.
