151 MHz Yagi antenna?
Hey guys and gals, I'm working on a design project for school and was wondering if someone could answer a question that our group has, we're mechanical engineering students and we know very little about antennae.
Background: We're thinking of making our own Yagi with some aluminum rods and copper wire and mounting it to an RC plane to track the motion and flight patterns of brown bats. The antenna will most likely be integrated into the wing, if possible. We plan to fly at an altitude of about 400ft and track the bats from there. Our goal is to have a directional antenna that can give us a general location of the bat (within a 100m^2 area).
Question: Is it possible to make a Yagi antenna that will pick up a 150-151MHz signal? If this is possible, are there any blind spots that I need to worry about?
Sorry if this is vague or confusing, but if someone is intrigued, I can provide more info later. Thanks!
The Yagi design focuses the radiation forwards and to some degree, backwards, signals from the sides are much attenuated.
The more elements you have, the more gain, but more directional the antenna becomes.
A three element Yagi has about 45° beamwidth (for example) while a 9 element may have only 20°.
I would recommend a design program like this but it wouldn't work on my Windows7 system :/
How large is the RC plane? A yagi for the frequency you're asking about is going to have x number of elements, each about 3 feet long on a boom that gets longer with each additional element. You can shorten the elements, probably, but that adds weight.
73
Pat K7KBN
Semper ubi sub ubi.
The RC plane will probably be about 2-3m wingspan. and the elements will most likely be embedded within the wings.
Another question I'm running into is blind spots. how much of an elevation angle am I going to get out a 3 element Yagi? Thanks for the help thus far.
Hi.
I think that we will need a lot more info from you.
Have you got a design for the plane in mind, not sure what sort of speed you will need but I would think that it will not have to be very fast so a larger wing will be needed so you may be able to get the beam in the wing. One like this maybe.
The engine may effect the antenna so a high wing plane would be better. Are you going to monitoring the trackers live if so how are you going to do it.
Just an idea what about a helicopter.
Last edited by mu0chn; Tue 6th Dec 2011 at 22:51.
A Yagi might not be the best idea for tracking randomly moving objects.
Something like one of these might be a better solution if you are able to follow in a car. With a little practise, they are very effective.
I presume the bats have already been caught & tagged with a transmitter...
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