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Thread: Antenna Isolation

  1. #1
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    Default Antenna Isolation

    I often use the antenna isolation calculators for horizontal separation, but these work with a single frequency.
    We install gear in the aviation area, around 130 MHz normally, and get interference between channels that are close.

    is anyone aware of a calculator that accepts 2 frequencies to determine minimum antenna spacing and takes into account the frequency spacing also ?


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    Quote Originally Posted by radiotechs View Post
    I often use the antenna isolation calculators for horizontal separation, but these work with a single frequency.
    We install gear in the aviation area, around 130 MHz normally, and get interference between channels that are close.

    is anyone aware of a calculator that accepts 2 frequencies to determine minimum antenna spacing and takes into account the frequency spacing also ?
    1) Power is additive. If you have two 100 watt (+50 dBM) stations there is +53 dBm.

    2) You need to consider inter modulation products.

    There are open source and proprietary IM calculators. The open source ones are on the web. The proprietary ones you must pay for and the better ones consider the bandwidth of the transmitter and the receiver.

    You or I could whip up a simple IM calculator on Excel, but it would miss many potential in channel receiver hits and totally miss the transmitter bandwidth at the harmonics.

    3) Better interference calculators examine the adjacent channel energy and transmitter noise and receiver defense.


    Transmit and receiver filters can be modeled in some calculator programs.



    Sent from my SM-T350 using Tapatalk

  3. #3
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    Quote Originally Posted by radiotechs View Post
    I often use the antenna isolation calculators for horizontal separation, but these work with a single frequency.
    We install gear in the aviation area, around 130 MHz normally, and get interference between channels that are close.

    is anyone aware of a calculator that accepts 2 frequencies to determine minimum antenna spacing and takes into account the frequency spacing also ?
    1) Power is additive. If you have two 100 watt (+50 dBM) stations there is +53 dBm.

    2) You need to consider inter modulation products.

    There are open source and proprietary IM calculators. The open source ones are on the web. The proprietary ones you must pay for and the better ones consider the bandwidth of the transmitter and the receiver.

    You or I could whip up a simple IM calculator on Excel, but it would miss many potential in channel receiver hits and totally miss the transmitter bandwidth at the harmonics.

    3) Better interference calculators examine the adjacent channel energy and transmitter noise and receiver defense.


    Transmit and receiver filters can be modeled in some calculator programs.



    Sent from my SM-T350 using Tapatalk

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    In some cases you simply cannot get around needing notch or pass filters to keep two signals from interfering with each other. Untimatly this may be the cheapest and most effective solution.

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    There was a nice chart at the back of the ACU-1000 manuals from JPS. Always had a laminated version with every Cache / Mobile Command Post.. There may also be one in the NIFOG, but I may be miss remembering that and don't have a guide here on my desk.

    https://www.dhs.gov/publication/fog-documents
    Last edited by code352; Sep 13, 2018 at 12:40 PM. Reason: Removed incorrect attachment