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Tech Support

    Antenna Evaluation: VSWR and Front-to-Back Ratio

    Voltage Standing Wave Ratio (VSWR)

    For a radio receiver or transmitter to deliver power to an antenna, the impedance of the radio and transmission line should match well with the impedance of an antenna. Voltage Standing Wave Ratio (VSWR) and return loss are two parameters used to determine whether an antenna is effectively impedance-matched to the line of transmission it is connected to. Often, there is a bandwidth range that antennas must satisfy and is defined in terms of VSWR.

    The lower the VSWR is, the better the antenna is matched to the transmission line and the higher the power delivered to the antenna. Furthermore, a small VSWR reduces reflections from the antenna. 1.0 is the minimum VSWR where there is no power reflected, and it’s the ideal condition for an antenna.

    Return loss, measured in dBi, which is an indicator of how much incident power is reflected to the source of the signal works in the opposite of VSWR. The higher the return loss, the more power to an antenna meaning you are losing less power and signal strength. Low return loss affects the antenna’s capability to radiate which in turn affects transmission efficiency. Overall, for an antenna to have good signal strength and efficient performance, VSWR should be low while dBi should be high


    Front to Back Ratio applies to Directional Antennas Only

    Front to Back Ratio is the measure of directivity of a directional antenna:  A ratio of the magnitude of directional radiation in an antenna, directed in a single direction, divided by the radiation pattern to the energy wasted in or by the antenna. 

    Increasing the gain of a directional antenna, is the same as increasing the front to back ratio. The best front to back ratio of a directional antenna is a large dish antenna such as 34dBi.

    Front to Back Ratio, which is expressed in dB, is important in situations where reverse coverage or interference needs to be minimized.  A low Front to Back Ratio means the less directional an antenna is hence poor reception from the front. A low Front to Rear Ratio can only be good when one is trying to pick up the signal from behind or the side of an antenna.

    When evaluating an antenna, Front to Back Ratio doesn’t necessarily fit with antenna gain (dBi). This is because an antenna can have poor front-to-rear ratio but have great gain. The overall performance will depend on the antenna you are using. In case of a directional antenna, both Front to Rear Ratio and antenna gain should be high for it to work efficiently and have a strong signal.

    The higher the ratio, the more directionally efficient the antenna is because a directional antenna always radiates some signal out of the back of the antenna. For an antenna to be said to be good, the Front to Back Ratio should be a minimum of around 15dBi. Then again, the antenna gain should be high raise the signal above the unavoidable amplifier noise hence increasing signal strength. 

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    50-Microns Gold Plating on RJ45 Connectors & Jacks: Up to 4X Throughput Increase

    The speed/throughput of an Ethernet Cable connection is increased by a multiple of as much as 4X, if the RG45 connections have 50 Micron Gold Plating, as compared to standard metal contacts.Gold is a much better conductor than any other common metal, and so the amount of signal loss is far less using gold, compared to cheaper [...]

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    dB, dBi, dBm dB(mW): Defined, Explained and Differentiated

    dB refers to the decibel, which is the unit of measurement of sound though it is also a relative measure of the power between two levels. Therefore dB is not an absolute measurement but rather a ratio.dB as a standalone unit represents loss or gain and does not have any dimension. It has to be [...]

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    Operate 2 Antennas from One Radio: Use a "Power Divider" or "Antenna Combiner" - NOT a T-adapter

    Do not use a "T connection" to get one AP to service two antennas: This causes many problems, further described below.  By "T connection," we mean T-adapter (see photo below) to combine two antennas onto the same antenna cable. A "T" is the incorrect way to split to antennas or transmitters. It results in a 2:1 [...]

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    LoRa: Long Range Wireless for Internet of Things (IOT): Frequency Bands Etc.

    LoRa is a wireless technology with incredibly low power usage, long range and secure data transmission for IoT and M2M applications. It is made on the chirp spread spectrum modulation technology which makes it efficient for long-range communication.   LoRa is short for long-range. LoRa Frequency BandsLoRa uses unlicensed frequency bands that are to be found worldwide. [...]

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    If Antenna frequency band exceeds needed range: Use Filter on system board to reduce excess band

    Example: You need only 860-960 MHz GSM band but the antenna covers 800-960MHz: One customer told us that using an antenna that includes 824-960 band allows too much interference, that comes from the low end of that band 824-860MHz.Our recommended solution is to add a filter in your system board (or AP [...]

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    4G & 3G Standards: LTE, GSM CDMA, ISM, WCDMA, HSPA

    LTE (4G), GSM (3G & 2G), CDMA (3G & 2G), and ISM. The fundamental differences between these four modern technologies is the way they transmit and receive information.LTE (Long Term Evolution) is a 4G communication standard designed to be 10x faster than standard 3G. the technology provides IP-Based communication of voice and multimedia and streaming [...]

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    ZigBee & XBee Radio for Internet of Things (IOT)

    Zigbee is a low-cost wireless technology used for short-range, low-power radio communication. ZigBee devices are almost exclusively limited to low bandwidth (1MHz) personal area networks. Most commercial ZigBee devices operate at 2.4GHz, although some devices run on other ISM bands such as 900MHz and 868 MHz frequency bands. ZigBee has a data transmission rate of 250 [...]

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    dBm to Watt Conversion Table

    Upgrading your antenna, even just a small increment in dBm, makes a HUGE impact on the range of your device: dBm 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Watts 1.0 mW 1.3 mW 1.6 mW 2.0 mW 2.5 mW 3.2 mW 4.0 mW 5.0 mW 6.0 mW 8.0 mW 10.0 mW 13.0 mW 16.0 mW 20.0 mW 25.0 mW 32.0 mW dBm 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Watts 40.0 mW 50.0 mW 63.0 mW 79.0 mW 100.0 mW 126.0 mW 158.0 mW 200.0 mW 250.0 mW 316.0 mW 398.0 mW 500.0 mW 630.0 mW 800.0 mW 1.0 W 1.3 W dBm 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 Watts 1.6 W 2.0 W 2.5 W 3.2 [...]

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    ISM Band of Frequencies and Allocation

    ISM means Industrial, Scientific and Medical frequency band. This is a band of radio and microwave frequencies clustered around 2.4GHz, reserved and designated for industrial, scientific and medical equipment that use RF. Industrial equipment like MRI machines, testing equipment, and some radio telescopes use this ISM band of frequencies. Smaller consumer devices such as microwave [...]

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    Signal Loss in Antenna Cables.  LMR-100, LMR-200, LMR-400 Gender of Antenna Cable Connectors is Counter-Intuitive


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