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what technical parameters decide the performance of a GSM/GPRS antenna? (excluding power consumption and size)

I have found out several antennas that have 3dBi gain. And I want to chose between them. Some are PCB antennas, some are external antennas and some are ceramic.

What other technical factors (polarisation pattern, VSWR etc) should I consider? And can someone please explain the combinational effect of such parameters?

P.S : Some technical terms given in antenna data sheets are very difficult to understand. But I am sort of certain that antenna performance may be not fully judged by dBi figure. Am I right to think a 2.5dBi antenna may be able to perform better than a 5 dBi antenna in a forest or harsh environments when such technical factors come into play?

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  • \$\begingroup\$ You should edit your original question to add a few details rather than write a whole new question. \$\endgroup\$
    – placeholder
    Commented Sep 28, 2014 at 10:24
  • \$\begingroup\$ @placeholder, then people like you complain saying there is more than one question. Kindly understand the question you referred, asks a completely different question. Do you have any answers to this question? \$\endgroup\$
    – Denis
    Commented Sep 28, 2014 at 10:57

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Here are a couple of things to consider.

An antenna with gain means it has some directionality. For instance, take the example of the satellite dish - it has a gain of many dB but needs to be pointing at the transmit antenna fairly precisely to receive the best signal. A few degrees out can mean barely receiving a signal at all. It works both ways - transmitting and receiving are governed by the directionality of the antenna. More directionality means more gain compared to the theoretical isotropic antenna (that has a gain of 0dBi and transmits equally in all directions.

An antenna with lower gain may perform better in some environments than an antenna with higher gain because the higher directional antenna may be difficult to align.

VSWR ulitmately informs you what the impedance mismatch betweeen antenna and coax might be - a high VSWR usually means either wrong impedance feeder cable or the antenna presents a complex to the feeder and some form of matching circuit is needed.

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