Posted: 12/30/2014 8:21:10 PM EDT
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So, I'm not keen on losing another RC aircraft. What are good ideas for DF antennas for 70cm?
I have a 13 element yagi, but that's not gonna cut it when going through the woods. Has anyone ever tried a loop? I mean, a 70cm loop is .7" in diameter, so I could VERY easily get that through thick brush. |
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Believe it or not, there are books about ham radio direction finding!
This one is rather dated: RDF Simplified To answer your question: Yes, you can use a small loop to DF a signal. With a loop you will get a figure-8 pattern. You can decrease the ambiguity by attaching a 1/4 wavelength wire to one side of the loop; this will make that side of the loop a tiny bit less sensitive, so it'll be a narrower pattern off that end. (does this make sense?) You may be able to get away with a 'body fade:' hold your HT close to your body and turn! This way, your body will shield your receiver from the transmitter and at its lowest sensitivity level, the transmitter will be directly behind you. To decrease the received signal even more, remove your antenna. |
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Cool. Thanks. I'm going to try the loop first, since it's small and easy to handle. Then I'll probably get into a tape measure 70cm yagi. Here's my 8el yagi: https://lh5.googleusercontent.com/-cPulsDG88Ik/U5Tiyf475DI/AAAAAAAAFo8/0GdEGN-n23I/w415-h553-no/IMG_20140608_182415.jpg A little off topic, but is your 2nd toe longer than your big toe? 
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You're thinking of using a gain antenna to DF with, which is fine, but since you're going through brush,
I'd strongly recommend one of two approaches: A mini time of arrival (TOA) DF unit like the handi-finder or, get a step attenuator and: use the peaking method on the signal strength meter (scroll down to the point where he talks able DFing with an HT) For your application either of those would be way preferable to lugging around a gain antenna. |
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Came here to post this...has a very good null. Posted Via AR15.Com Mobile Quoted:
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I have been tinkering with a 2m moxon beam, it might be suitable for your purpose. Came here to post this...has a very good null. Posted Via AR15.Com Mobile Wow. 25 dB front to back? Sign me up! |
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Wow. 25 dB front to back? Sign me up! Quoted:
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I have been tinkering with a 2m moxon beam, it might be suitable for your purpose. Came here to post this...has a very good null. Posted Via AR15.Com Mobile Wow. 25 dB front to back? Sign me up! You work backwards, so you look for the null, target is directly behind the antenna. |