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Wireless VHF from 3-element Yagi

Discussion in 'Radio and Communications' started by Grisdale, May 27, 2015.

  1. Grisdale

    Grisdale New Member

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    I am interested in wirelessly transmitting a signal from a 3-element yagi in the 148-174MHz or 216-222 MHz range to a hand held receiver. The yagi has a female BNC connector to a RG58/U coaxial cable. This is specifically for mobile wildlife tracking applications. Currently I use a coaxial cable and it is a huge hassle to uncoil and recoil every time. I was wondering if anybody knew of a product (the smaller the better) or a way to cheaply make a transmitter that can replace the coaxial cable. Any ideas would be greatly appreciated, thank you.

    An example of the kind of yagi I use can be found here:
    https://wildlifematerials.com/store/product.php?s=m&id=38&cat=

    The receiver is this model:
    http://www.com-spec.com/r1000/index.html
     
  2. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    As you said, this equipment is specifically for tracking wildlife. Transmitting through the Yagi (instead of using the Yagi for receiving an animal's radio collar) is not permitted under the license-free rules that apply to the use of the frequencies reserved for wildlife tracking.

    What are you trying to do?
     
  3. Grisdale

    Grisdale New Member

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    Maybe transmit was the wrong word. The yagi would be receiving the signal from the VHF transmitter on the collared animal like normal usage, but I want the signal to travel wirelessly to the receiver instead of through the coaxial cable.
     
  4. dave

    Dave New Member

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  5. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    No such thing, use the cable.
     
  6. cowboybob

    cowboybob Well-Known Member Most Helpful Member

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    My emphasis.

    Welcome to ETO, Grisdale!

    Perhaps obvious, but a shorter cable won't suffice?
     
  7. tunedwolf

    tunedwolf Well-Known Member

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    Build a receiver that mounts directly onto the rear of the antenna :)
     
  8. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    That's what I use for balloon payload tracking, ELTs, and bunny-hunts. Looks just like this one...
     
  9. Willen

    Willen Well-Known Member

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    Wildlife tracking and receiving is amazing to me. I heard explorer are allowed to fit a transmitter to the animal but weight of the transmitter should be limited to 2% of the animal. Some small birds are just few grams and explorer were fitting tiny transmitter, looked like a Needle of syringe. I don't know how they make such tiny transmitter with built in battery and Antennna too. They were receiving the bird from very far using such 3 element Yagi. Probably the receiver was the most sensitive!
     
  10. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    We used the lower HF band to make Polar Bear tracking transmitters, where they were using a plane for tracking hibernation patterns in the late 70's in Northern Manitoba.
     
  11. Willen

    Willen Well-Known Member

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    Hi, Why lower band of HF? It needs longer dipole, maybe which was not portable. Do it mean that the lower HF is nice than VHF to transmit through ice. Signal need to cross ice if bears are in hibernation inside ice cave.
     
  12. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    Friis losses are higher at VHF but antenna gain may also be worse if length is much shorter than 1/4W.
    Threshold of detection is reduced by noise reduction of narrower IF BW and only needs to be wide enough to detect burst pulse width and any drift of f. Such as 50ppm or better if using 1 ppm TCXO. Avg. Power in Tx is a function of Ppk*tOn/tCycle rate so increasing peak power and reducing duty cycle are tradeoffs with filter noise BW. I recall Tx antenna was a loop around neck collar.
     
    Last edited: Jul 19, 2015

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