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Wireless Antenna Strength

  1. Aug 14, 2006 #1
    Ok. I'm currently trying to understand antenna strength in the wireless cards you find for your computer. Let's say that I have a wireless card with a certain "receiver sensitivity". How exactly do I read this?
    I'm trying to find an explanation or perhaps a reference to something that can explain this to me. So if I wanted to find another card, perhaps with a stronger antenna...or one that was better equipped to receive signals better what exactly would I be looking for?
  2. jcsd
  3. Aug 15, 2006 #2


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    "OFDM" refers to a specific kind of digital modulation, orthogonal frequency-division multiplexing. The available spectrum is broken up into a large number of small, adjacent channels. Each channel is then used to carry a single BPSK, PAM, or QAM signal.

    PER refers to packed encoding rules, which is essentially a "data compression strategy" used to reduce the number of symbols needed to transmit a given piece of information.

    The sensitivity itself is given in dBm, or decibels with respect to one milliwatt.

    1 dBm is equivalent to one milliwatt.
    -10 dBm is equivalent to 0.1 milliwatt.
    -20 dBm is equivalent to 0.01 milliwatt.
    -70 dBm is equivalent to 0.0000001 milliwatt, or about one tenth of one billionth of a watt.

    The more negative the receiver's sensitity spec, in dBm, the more sensitive is the receiver.

    - Warren
  4. Aug 16, 2006 #3
    So I wanted let's say a PCI card or USB. I could just look at the receiver sensitivity and find one in which the dBm is more negative and that card would essentially pick up my wireless network...let's on the other end of my house better than the PCMCIA card I gave a link to above?
  5. Aug 16, 2006 #4


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    There are many other factors. I believe the specified value is actually the receiver sensitivity, and does not include issues like antenna directionality, upstream analog processing losses, etc. The digital receiver itself is an integrated circuit at the end of a long analog signal path.

    I personally would not make a determination of which card to get solely by its receiver sensitivity spec, unless one card's sensitivity is more than, say, 3-6 dB better than an another's.

    Keep in mind that WiFi standards include a wide range of speeds. As the signal degrades in quality, smaller signal constellations are used -- you'll still receive network service, but it'll be lower speed.

    I'd suspect that most consumer wireless products are relatively similar in range performance. If you're having trouble with one brand of card, you're more likely to solve the problem by moving the access point than you are by buying a different wireless card.

    - Warren
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