Category Archives: Tech - Page 15

Radio over VoIP

Posted by on March 5, 2006 Comments Off on Radio over VoIP

In a followup to an earlier article about the Cisco IPICS system I have received some additional information that seems to indicate my preliminary analysis was correct. If you remember when Cisco launched their IPICS ’emergency communications system’ I suggested it was really more of a way to tie existing communications systems together than a new system itself.

It seems that Cisco has been looking into this for a while and ostensibly created this product to fill an internal company need for connecting disparate communications systems. This case study explains how Cisco created a Land Mobile Radio (LMR) over IP product to fill a need to communicate with their own security personnel. The end product is described in this Cisco whitepaper entitled “Cisco Land Mobile Radio over IP Solution Reference Network Design”.

The LMR over IP product is a card which can be installed in any of the voice capable Cisco routers and provides an interface that connects full-duplex VoIP datastreams to speaker, mic, push-to-talk (PTT) half-duplex devices. Signaling is via standard H.323 and the card uses RTP audio with a variety of codecs. The card used is called a VIC Ear and Mic (E&M) interface and was originally used to connect VoIP to some legacy PBX hardware. Technical information about the E&M interface can be found in this technical publication. If your LMR equipment supports a half-duplex T1 that can be used as a trunk interface instead.

As a friend pointed out the existence of support for this type of configuration presents some interesting ideas for amateur radio VoIP projects. Without going into too much detail the current preferred methods of connecting amateur radio stations with VoIP is to use either the Echolink or IRLP project. Both of these have a significant number of problems, one of which is that they require a computer to be attached to the radio. It would be much nicer to attach a (more stable) router to the radio instead. This merits some more research. Once you got a radio attached to a VoIP phone system such as Asterisk there’s all kinds of interesting possibilities.

Rocket Man

Posted by on February 28, 2006 Comments Off on Rocket Man

If you haven’t heard about Juan Manuel Lozano perhaps you should. Lozano has devoted most of his life to building a personal jetpack at his home 50 miles south of Mexico City. Along the way he has invented and sold a distiller for 90% pure Hydrogen Peroxide (which he uses to fuel his jetpack) and a super efficient “Penta M” catalyst pack which converts the fuel into steam. He has no formal education beyond high school and only standard aerobatic pilot training. Popularized in the 1960s by Wendell Moore of the Bell Aerospace company the devices have been featured in everything from James Bond films to the 1984 Summer Olympics. Lozano has successfully completed a series of tethered test flights with his rocket pack and hopes to perfect and begin selling his design for $350,000 each. Considering that only 12 people have ever flown untethered rocket packs that’s no small feat. It’s also one that has earned Lozano and his company, Technologia Aerospacial Mexicana, a prime article by Larry Smith in the March 2006 Popular Mechanics magazine entitled “Ready for Takeoff?“. It’s a great article and I encourage you to read up on this amazing tinkerer and backyard rocket scientist.

A Real Scanner

Posted by on February 27, 2006 Comments Off on A Real Scanner

While it’s prohibtively expensive to build the Equinox radio scanner probably represents the pinnacle of radio scanning equipment today. A fully remote controllable PC based radio (RF) scanner this is truly the Cadillac monitor.

From its home in the Seattle, Washington area, the Equinox receiver provides continuous, remotely-accessible coverage of the DC-1 GHz spectrum on a 24-hour basis.

While it would be a bit much for individual hobbiests to build one of these it would be cool to see scanning clubs such as Minnesota based ScanFan get together and buid one for community use. The internet provides a great way of participating in this increasingly expensive hobby (as more systems go digital) if we could allow for some remote control and data from the reciever(s).

Open Source City

Posted by on February 26, 2006 Comments Off on Open Source City

LinCity looks like a great Linux clone of the traditional Maxis game, SimCity. Now in an updated form LinCity-NG now has an isometric 3D view similar to that found in SimCity 2000, arguably the best version of the classic game.

GPS Maps

Posted by on February 26, 2006 Comments Off on GPS Maps

I’ve had a bluetooth GPS for a few months now and have really enjoyed it. One of the more fun things I like to do is create virtual tracks of where I’ve been. One website that can help you do just that is GPS Visualizer.

GPS Visualizer allows you to upload NMEA GPS logs to their site and export maps in a variety of formats. One of the most compatible formats uses a Google Maps overlay. They also support the Google Earth overlay and KML formats and several static formats such as SVG and JPEG/PNG using a variety of map sources.

A Slimmer Real Player

Posted by on February 24, 2006 Comments Off on A Slimmer Real Player

Those of us who have been on the ‘net for a while can remember the heyday of Real Player. One of the first ways to squeeze passable audio and video down narrow dialup connections Real Player was a boon to the then emerging streaming media market. Somewhere along the way Real Media lost this focus and tried to enter the media library/management/player category with the RealOne product. Ever since then it seems the amount of advertising and junk that comes with the player has discouraged many from installing it. There have been some alternatives available (RealAlternative comes to mind) but these enjoy limited success as they don’t support the latest features and are rejected by some sites. For several years I ran an old copy of Real Player G2 which was about the last unbloated version of the software but that no longer works at many sites. It has even become hard to find the free version of the standard Real Player and it still comes with bloatware and advertising.

One alternaitve that I’ve been using for a while and seems to work well is the “Real Player Enterprise” edition of the software. Designed for companies who revolted against installing Real Player becasue of all these problems, this client is ad-free and you can turn off all of the annoying features. It also is based on the current version of Real Player so it should be accepted anywhere with Real Media files. Good luck trying to find a link to this from the homepage though!

You can learn more about this program on the Real Player Enterprise website and download a free copy from the download page. Stream on.

Speedy Reader

Posted by on February 22, 2006 Comments Off on Speedy Reader

By now most netizens are familiar with the ubiquitous Portable Document Format (PDF) file. Commonly used to distribute printed material online PDF files have been traditionally opened with Adobe’s Acrobat Reader (now just Adobe Reader) but that has become quite a slow and bloated program over the years. I don’t know about you but I would rather it not take two minutes just for a program to load so I can read a simple one page document. While it may not have all the bells and whistles associated with the Adobe Reader I’ve found that the free Foxit Reader is a great Microsoft Windows compatible alternative viewer for PDF files. Taking just a second to load and coming in at less than 1 MB this is a splendid example of putting bloatware on a diet. You may want to keep a copy of Adobe Reader handy for filling out PDF forms or in case you have a particularly complex file to open but for the average PDF Foxit Reader certainly is a speedy alternative.

Snowflake Preservation

Posted by on February 21, 2006 Comments Off on Snowflake Preservation

Have you ever wanted to save a snowflake for photography or just to look at it later. In 1931 Wilson A. Bentley published “Snow Crystals” which contains over 2,400 photographs of snowflakes taken over 47 winters. When Bentley took his photographs he had to work quickly before heat from his body melted the subject. Since that time we have developed a number of ways to preserve snow crystals.

In 1951 Vincent J. Schaeffer pioneered a method using a coating of polyvinyl formal in ethylene dichloride, but ethylene dichloride is now classed as toxic and a suspected carcinogen making it much more difficult for the average hobbyist to obtain. Other chemists have suggesting using chloroform instead but it is also quite difficult to obtain. Still others have tried plastic, hair or workable fixative spray with only limited success. I have also learned of a method that uses clear nail polish to preserve the snowflake.

In 1979 chemist Tryggvi Emilsson developed a process using cyanoacrylate, commonly referred to as “super glue”. Cynoacrylate works best on objects that have some moisture in them, because snowflakes are made from water they are fanstastic candidates for superglue preservation. Start by placing microscope slides, coverslips and superglue (the runny type, not the gel type) outside on a day when it is 20 degrees Farenheit or colder out. The materials will need time to cool down to the ambient temperature. Catch snowflakes on the slides or carefully pick them up and place them on a slide with a cold tweezers. Place a drop of superglue over a snowflake on the slide and carefully drop a coverslip over the top. Be carful not to press down hard and keep the heat from your hands away from the flake. Keep the slide in a freezer for a week or two until the glue completely hardens before allowing the slide to warm up.

This information is based on an article by Theodore Gray in the March 2006 volume of Popular Mechanics. Check out his “Gray Matter” article there for more information on the Emilsson method.

Subnetting

Posted by on February 20, 2006 Comments Off on Subnetting

Subnetting is the art of dividing one network into many by use of a subnet mask. In my experience one of the most difficult things for networking students to master is subnetting. When they need some kind of new viewpoint on the subject I usually send them to LearnToSubnet.com. This site has been around for several years now and offers free mini-lectures on this important topic. All told there are several hours of video there and you may need to refer to some of the sections multiple times to gain a full understanding of subnetting but it is one of the better sites out there for this.

Deploying Windows XP

Posted by on February 20, 2006 Comments Off on Deploying Windows XP

Backin August, 2004 I mentioned the XPCREATE utility which can be used to slipstream service packs and hotfixes into Windows XP installation CDs. With Windows XP continuing to age and hotfixes still accumulating there are even better tools availible to ease the installation process. The most widely recognized tool today is nLite. This program has a clean and easy to use interface that allows you to create deployment CDs for Windows XP that include all of the latest hostfixes plus craft an unattended installation disc or one with custom default settings. Previously creating discs such as these was only possible with a deep understanding of how Microsoft install CDs worked and writing a lot of INF files by hand. Even for simply getting patches onto your install CD nLite is a great option.