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How to choose a mobile 3G/4G cellular multi-band antenna for in-vehicle applications (taxi, utility, etc)

Posted by Michael Crudele on

Arcadian Inc. is the single largest suppier of vehicular multi-band antenns for taxi cabs in North America.  We have spent countless hours with our clients researching the best antennas for their in-taxi systems used for GPS tracking, infotainment & mobile credit card processing.  If you have an application where you are using in-vehicle 3G/4G cellular modems (like Sierra Wireless GX440 or Cradlepoint, contact me for antenna suggestions.)  

 

Recently, I was working with a potential client who was utilizing the Wilson 301106 antenna, which is now obsolete.  Of course, I was working to move them over to one of our antennas, and the client's argument was that the Wilson antenna was significantly cheaper thatn anything we could offer.  So I probed further, and asked "how is that antenna actually working out for you?"  The response was NOT so postive.  Apparently, this company was having ALOT of issues in the field with taxi cab drivers struggling to get a cellular connection, and thus being unable to process credit cards in a timely fashion.  

 

So, I sat down and spent some time digging into their situation, and theorized that the main problem was that they were operating their taxi cab fleet in a part of the city that was particularly densly packedwith tall buildings, thus creating so-called "urban canyons."  

 

In the end the antennas that I ended up recommending are LOWER gain than the Wilson antenna, (but much higher “efficiency”) and here is why that is a GOOD THING for people facing a similar technical dilemma, and suffering with issue of lack of 3G/4G cellular connectivity to their vehicular modems.  The issues may very well be the choice of antenna.  You see, most people that are not antenna "experts"  do a bit of research, and find that antenna "Gain" is the measurement of an antennas strength, or at least that is how most people understand it.  That leads them to belive that more gain is better, and is the cure all for any cellular connectivity problems.  Gain is typically measured in dBi or "decibals beyond the isotrope."  To over-simplify it, the highter the dBi, the farther the antenna's wireless signal will travel.  0 dBi gain is also known as "unity gain"  More on this below...

 

Unity gain or zero gain has a perfectly spherical shape, it transmits up, down, and sideways with equal power.  The antennas that I ultimately recommended for this applications are LOW GAIN for urban environments – why?  Because most of the Verizon, AT&T, and Sprint/T-Mobile 3G/4G cellular signals are coming from antennas mounted on towers or from the top of buildings, and you want an antenna that can not only reach “outward” but more importantly, reach “upward.”  The trade-off of designing the antenna in this way is that it has less “reach” from side to side.  However, in these metropolitan cities or "urban canyons" where there are huge buildings on every side, that gain basically goes to waste, as it simply bounces off the buildings and never makes a connection to the Verizon, AT&T or Sprint/T-Mobile antennas that are up on top of the buildings.

 

The previously mentioned Wilson antenna was designed for rural environments, where the cellular signal is typically far away, (but there are no large buildings providing interference) so what they do is they “compress” the middle of the signal of the antenna so that more energy reaches “outward” vs. “upward” 

 

So, in actuality, in an urban environment, you want to minimize the gain (sideways power) and by keeping the gain low, you maximize the upward reach of the antenna, which is what you want.  Take a look at the graph below. 

 

Description: antenna.gif - 8.11 K

 

Would you consider fulfilling your next antenna requirement with me, and seeing for yourself?

 

Feel free to contact me or a member of our staff for ANTENNA HELP on your next project.  At Arcadian, we are THE ANTENNA EXPERTS and we are here to help.  

 

All the best, 

Mike Crudele: mikec@arcadianinc.com 1-888-925-5967

 

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