Vertical separation in antennas

Archived from groups: alt.internet.wireless (More info?)

I have 2 SA24-120-16 antenna's on a tower. Still learning alot about
wireless broadband as I go. currently they are at the same height on the
tower and near each other. Can this cause interference and if so, how far
apart should they be vertically and horizonatlly. They are set for a
vertical polarity.

Thanks!
4 answers Last reply
More about vertical separation antennas
  1. Archived from groups: alt.internet.wireless (More info?)

    On Fri, 26 Nov 2004 23:19:58 -0800, "me" <here@i.am> wrote:

    >I have 2 SA24-120-16 antenna's on a tower. Still learning alot about
    >wireless broadband as I go. currently they are at the same height on the
    >tower and near each other. Can this cause interference and if so, how far
    >apart should they be vertically and horizonatlly. They are set for a
    >vertical polarity.

    Antennas do not cause interference. Radios cause interference.

    So far, all I know is that there are two antennas on a tower at some
    unspecified seperation and orientation. No clue as to how much coax
    is between the antennas and their respective radios, what type of
    radios, length of coax cables, and whether this is part of some power
    splitter or amplifier arrangement.

    The RF-Linx SA24-120-16 is a 120 degree sector antenna, with 16 dB of
    gain. If you mount these next to each other, but rotate them so that
    the 120 degree sector pattern does NOT overlap, you will probably have
    enough isolation between antennas. If you look at the typical
    cellular monopole, that's the way they do it. 3ea 120 degree sector
    antennas wrapped around the pole.

    The point at which your unspecified receiver overloads is in the data
    sheet. -30dBm is typical. If you do have overlap, you can use the
    antenna patterns:

    http://www.rflinx.com/Antenna%20Datasheets-html/2.4GHZ/RFLSA24%20VERTICAL%2090-120%20SECTOR.htm
    to estimate the amount of signal coupling between antennas.
    http://my.athenet.net/~multiplx/cgi-bin/isolation.cgi
    Subtract out any coax losses, and estimate how much signal is
    appearing at the receiver from the other transmitter. If over perhaps
    -30dBm, you will have a desensitization problem. Note that the
    interfering transmitter does NOT need to be on the same channel.

    A more serious and incidious problem is intermodulation products
    caused by two transmitters mixing together. This can easily happen
    when two or transmit antennas are too close. In commercial VHF/UHF
    systems, isolators, circulators, and cavities are used to provide
    additional isolation. These are not very economical at 2.4Ghz, so
    physical isolation is necessary.

    Rant: Numbers and specifics, not prose.


    --
    Jeff Liebermann jeffl@comix.santa-cruz.ca.us
    150 Felker St #D http://www.LearnByDestroying.com
    Santa Cruz CA 95060 AE6KS 831-336-2558
  2. Archived from groups: alt.internet.wireless (More info?)

    "me"
    | I have 2 SA24-120-16 antenna's on a tower. Still learning allot about
    | wireless broadband as I go. currently they are at the same height on the
    | tower and near each other. Can this cause interference and if so, how far
    | apart should they be vertically and horizontally. They are set for a
    | vertical polarity.

    I'd need a bit more info to make an educated response but with what you have
    posted:

    Horizontally spaced antenna typicallky experience more mutual interference
    than vertically spaced antenna. The idea configuration would be vertical
    spacing coaxially in line.

    That said there are two type of potential interference. The first has to do
    with RF reception and is frequency/channel dependant. The second has to do
    with parasitic reradiation. In some cases this is the desired effect and
    produces directivity. In other case it can cause multi-plathing which is
    typically (but not always) undesired.
  3. Archived from groups: alt.internet.wireless (More info?)

    Sector antennas dont have near the problems as other antenna types. I see
    sectors on antennas all the time
    mounted 6 at a time. Are you experiencing interference or just curious. Are
    they on the same channel?


    "Not Me" <me@privacy.net> wrote in message
    news:30s9c7F34mlkaU1@uni-berlin.de...
    >
    > "me"
    > | I have 2 SA24-120-16 antenna's on a tower. Still learning allot about
    > | wireless broadband as I go. currently they are at the same height on
    the
    > | tower and near each other. Can this cause interference and if so, how
    far
    > | apart should they be vertically and horizontally. They are set for a
    > | vertical polarity.
    >
    > I'd need a bit more info to make an educated response but with what you
    have
    > posted:
    >
    > Horizontally spaced antenna typicallky experience more mutual interference
    > than vertically spaced antenna. The idea configuration would be vertical
    > spacing coaxially in line.
    >
    > That said there are two type of potential interference. The first has to
    do
    > with RF reception and is frequency/channel dependant. The second has to
    do
    > with parasitic reradiation. In some cases this is the desired effect and
    > produces directivity. In other case it can cause multi-plathing which is
    > typically (but not always) undesired.
    >
    >
  4. Archived from groups: alt.internet.wireless (More info?)

    Simply, in theory you should place your antennas about 120-300cm horizontally
    from each other, and at least half of their length in vertical.

    This is, of course, only theory. Everything depends on your radio's output
    power.
    When talking about wifi I think that a couple of centimeters is enough.
    (tested)
    But it also depends on antenna's F/B ratio...

    m.


    --
    Marcin Lukasik
    Milea Wireless Communications, http://milea.pl
    phone/fax/mobile: (++48) 13 4480070 / 13 4481148 / 509 390 490

    ,,the only difference between men and boys is the price of their toys''
Ask a new question

Read More

Wireless Broadband Internet Wireless Networking