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Thread: MURS Antenna Upgrade

  1. #1

    Default MURS Antenna Upgrade

    I have a base station transceiver Model M538-BS Multiple Use Radio Service (MURS) by Dakota Alert.

    I have the transmitter for the sensor about 15 feet up in a tree about 1500 feet away.

    That transmitter and underground sensor are known as the "Murs Alert Probe System" (MAPS).

    That is also made by Dakota Alert.

    The transceiver is in my living room.
    The reception is somewhat marginal.
    How can I improve my antenna situation to get better reception?
    I have seen things like this.

    https://www.amazon.com/d/Antennas/Fi...s=murs+antenna

    and this

    https://www.amazon.com/Centerfire-Me...s=murs+antenna

    Is this a direction I want to go? and how would I connect the antenna to the Model M538-BS?
    I know the connector on the 538 is a standard BNC.
    and what cable?

    Thank you

  2. #2

    Default

    I would try repositioning the receiver first. That product should handle 1500 feet easily if the path is unobstructed. There are various reasons the signal could be weak. Is there a metal building in the path? Large hills?

    One reason VHF could behave that way is multipath fading. It is quite possible repositioning the receiver by a foot or so could clear it up. If the house has metal siding, try a window. Knife edge diffraction is useful at VHF, so there is a good chance at finding a "sweet spot".

    An external antenna is a viable option, but keep in mind that most coax is very lossy at VHF, keep the coax run as short as possible if you attempt that. There is little benefit to adding 3dB gain with a better antenna if the coax will eat 4dB. After looking at those antenna prices, I would just build one. If you know what MURS channel the device uses, making a ground plane antenna is very easy. There are calculators all over the internet.

    MURS 1 = 151.820 MHz
    MURS 2 = 151.880 MHz
    MURS 3 = 151.940 MHz
    MURS 4 = 154.570 MHz
    MURS 5 = 154.600 MHz

    https://m0ukd.com/calculators/quarte...na-calculator/

  3. #3

    Default

    Quote Originally Posted by brandon lind View Post
    I would try repositioning the receiver first. That product should handle 1500 feet easily if the path is unobstructed. There are various reasons the signal could be weak. Is there a metal building in the path? Large hills?

    One reason VHF could behave that way is multipath fading. It is quite possible repositioning the receiver by a foot or so could clear it up. If the house has metal siding, try a window. Knife edge diffraction is useful at VHF, so there is a good chance at finding a "sweet spot".

    An external antenna is a viable option, but keep in mind that most coax is very lossy at VHF, keep the coax run as short as possible if you attempt that. There is little benefit to adding 3dB gain with a better antenna if the coax will eat 4dB. After looking at those antenna prices, I would just build one. If you know what MURS channel the device uses, making a ground plane antenna is very easy. There are calculators all over the internet.

    MURS 1 = 151.820 MHz
    MURS 2 = 151.880 MHz
    MURS 3 = 151.940 MHz
    MURS 4 = 154.570 MHz
    MURS 5 = 154.600 MHz

    https://m0ukd.com/calculators/quarte...na-calculator/
    Thank you for the reply.

    Can you think of any reason for this? or maybe it's just the units degrading (caps?).>>>

    I had one unit working good in the tree for about 10 years.

    Then all of a sudden it became very marginal (not acceptable).

    I had another unit that worked well for a couple years in another location...then I had it on the shelf for a couple years....I replaced the unit that worked good for 10 years (than now is marginal) with the shelf unit. That unit also worked very marginal in the tree.

    Then I had a new unit. That's in the tree now and seems to work but has a little more static than the unit that worked for ten years. Any thoughts on this? Could the two units have become weak? Or could it be an issue with my receiver?

  4. #4

    Default

    The DBJ-2 has a MURS version https://edsantennas.weebly.com/

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