Cody Taylor

I didn’t know enough about antenna gain to define it if someone asked me to so I did some research. Gain itself seems to be a tricky term to define, so I’m going to have to explain a few other things along with it.

Antenna gain is basically measure of the effectiveness of a directional antenna as compared to a standard nondirectional antenna.

One of the major parameters used in analyzing the performance of radio frequency (RF) communications links is the amount of transmitter power directed toward an RF receiver.

This power is derived from a combination of:
1 – Transmitter power
2 – The ability of the antenna(s) to direct that power toward an RF receiver(s).

Directivity
The directivity of the antenna is determined by the antenna design. Directivity is the ability of an antenna to focus energy in a particular direction when transmitting or to receive energy better from a particular direction when receiving. To determine the directivity of an antenna, we need a reference antenna with which to compare our antenna’s performance.

Over the years there have been several different reference antennas used. Today an isotropic radiator is preferred as the standard antenna for comparison. The isotropic antenna transmits equal amounts of power in all directions (like a light bulb).

To increase the directivity of a bulb’s light (the antenna’s energy), similar to a flash light or automobile head lamp in this example, a reflector (antenna) is added behind the bulb. At a distance, in the light beam, the light bulb now appears to be much brighter. The amount that the bulb appears brighter compared to the bulb without a reflector is the directivity of the reflector (antenna).

When the directivity is converted to decibels we call it the antenna gain relative to an isotropic source (dBi). Typically the higher the gain, the more efficient the antenna’s performance, and the farther the range of the antenna will operate. Roughly for every 6 dBi in gain, you double the range of the antenna.

It should be noted that many issues need to be considered when selecting the “best” antenna for the application, and you should discuss any antenna selection with someone knowledgeable in RF radiation and antenna performance.

So a better definition of antenna gain is:
A relative measure of an antenna’s ability to direct or concentrate radio frequency energy in a particular direction or pattern. The measurement is typically measured in dBi (Decibels relative to an isotropic radiator) or in dBd (Decibels relative to a dipole radiator).

The companies are pairing Cisco’s mobile WiMax infrastructure with Clearwire’s ecosystem of partners to deploy mobile broadband.

Barence writes “Baby monitors and wireless TV transmitters are responsible for slowing down Wi-Fi connections in built-up areas, according to a report commissioned by British telecoms regulator Ofcom. The research smashes the myth that overlapping Wi-Fi networks in heavily congested towns and cities are to blame for faltering connection speeds. Instead it claims that unlicensed devices operating in the 2.4GHz band are dragging down signals. “It only requires a single device, such as an analogue video sender, to severely affect Wi-Fi services within a short range, such that a single large building or cluster of houses can experience difficulties with using a single Wi-Fi channel,” the report claims.”

Read more of this story at Slashdot.

bsharma writes to let us know about a little goodie that we will be able to buy starting May 17: a battery-powered, rechargeable, cellular, Wi-Fi hot spot that you can put in your pocket. “What if you had a personal Wi-Fi bubble, a private hot spot, that followed you everywhere you go? Incredibly, there is such a thing. It’s the Novatel MiFi 2200, available from Verizon starting in mid-May (0 with two-year contract, after rebate). It’s a little wisp of a thing, like a triple-thick credit card. It has one power button, one status light and a swappable battery that looks like the one in a cellphone. When you turn on your MiFi and wait 30 seconds, it provides a personal, portable, powerful, password-protected wireless hot spot. … If you just want to do e-mail and the Web, you pay a month for the service (250 megabytes of data transfer, 10 cents a megabyte above that). If you watch videos and shuttle a lot of big files, opt for the plan (5 gigabytes). And if you don’t travel incessantly, the best deal may be the one-day pass: for 24 hours, only when you need it. In that case, the MiFi itself costs 0.” The device has its Wi-Fi password printed on the bottom, so you can invite someone to join your network simply by showing it to them.

Read more of this story at Slashdot.

Not-A-Microsoft-Fan writes with this excerpt from The Coffee Desk: “Netbooks are making huge waves within the hardware and software industries today, but not many would believe that the whole Netbook craze actually started back around 1996 with the Toshiba Libretto 70CT. Termed technically as a subnotebook because of its small dimensions, the computer is the first that fits all of the qualifications of being what we would term a netbook today, due in part to its built-in Infrared and PCMCIA hardware, and its (albeit early) web browsing software. The hardware includes the two (potentially) wireless PCMCIA and infrared network connections, Windows 95 OSR 2 with Internet Explorer 2.0, a whole 16MB of RAM and a 120Mhz Intel Pentium processor (we’re flying now!).”

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narramissic writes “In a recent blog post, Josh Fruhlinger muses on the possibility of 3G radio receivers turning up in future Mac notebooks (as foretold by Apple job postings and the mention of WWAN hardware in Snow Leopard beta releases). ‘At first glance,’ says Fruhlinger, ‘this seems like a reasonably awesome idea.’ But will the target market be willing to take on the additional telecom charge? ‘And, more to the point,’ he says, ‘most of us have gotten accustomed to the idea of one Internet connection per household, shared with a wireless router. The latter idea could be covered by a router that connects to the Internet over a 3G connection — something like the MiFi hotspot. It wouldn’t surprise me if Apple had such a thing in the pipeline, an Airport station (Airport Mobility?) that didn’t need to be plugged into the wall. That would explain the search for 3G experts, anyway.'”

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Hugh Pickens writes “Google, the wireless industry, and consumer advocates have come together to support a bill that would require the federal government to take a complete inventory of the national airwaves to determine what spectrum is being used, how it is being used and who is using it. The government needs to clean up its sloppy record keeping, they say, or the US risks running out of wireless capacity with the increasing use of the mobile Internet. ‘Radio spectrum is a natural resource, something that here in the US is owned by all of us American citizens,’ wrote Richard Whitt, Google’s counsel for telecom and media. ‘Most of us don’t give it much thought — and yet use of these airwaves is precisely what makes many of our modern communication systems possible.’ The new law, if passed, would require the Federal Communications Commission and the National Telecommunications & Information Administration to report on the use of all spectrum bands between 300 megahertz and 3.5 gigahertz, including information on the licenses or government user operating in each band and whether the spectrum is actually in use. The unusual alliance between Google, public interest groups, and big telecommunications companies may be temporary. The telecom companies want to have the opportunity to buy any extra spectrum at an auction while Google advocates the use of new technologies that would allow the spectrum to be shared by whoever needs it.”

Read more of this story at Slashdot.

judgecorp writes “A new vendor group has promised a Gigabit wireless specification by the end of this year. The Wireless Gigabit (WiGig) spec is apparently 80 percent done and, since it is aimed at high-definition TV, it has to go at more than 3Gbps. There’s around 7GHz of spectrum freely available in the 60GHz band, so it’s technically feasible, and with all the major Wi-Fi silicon vendors on board (as well as Microsoft, Dell, Nokia and others) WiGig looks to have the political muscle too. They should be aware of the Sibeam-led WirelessHD group, though, already in the 60GHz space, and Ultrawideband (UWB) is not dead, as there are actual, real UWB products.”

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coondoggie writes in with a Network World piece that begins “A range of companies with wireless LANs are discovering that 50% to 90% or more of Ethernet ports now go unused, because Wi-Fi has become so prevalent. They look at racks of unused switches, ports, Ethernet wall jacks, the cabling that connects them all, the yearly maintenance charges for unused switches, electrical charges, and cooling costs. So why not formally drop what many end users have already discarded — the Ethernet cable? ‘There’s definitely a right-sizing going on,’ says Michael King, research director, mobile and wireless, for Gartner. ‘By 2011, 70% of all net new ports will be wireless. People are saying, “we don’t need to be spending so much on a wired infrastructure if no one is using it.”‘ … There is debate over whether WLANs, including the high-throughput 802.11n networks, will be able to deliver enough bandwidth.” Cisco, which makes both wireless and wired gear, has a spokesman quoted calling this idea of right-sizing a “shortsighted message from a wireless-only provider. It’s penny-wise and pound-foolish.”

Read more of this story at Slashdot.

In the latest changes to AT&T’s service terms, it looks like the company is trying to exempt its own video services while prohibiting competing services like the Slingbox. It’s not very “Internet” when the ISP is picking and choosing what legal activities you may and may not do with your connection.