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Old Oct 25, 2010, 05:35 PM
IBCrazy is offline
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Engineer for Christ
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Amherst, VA
Joined Jun 2006
11,092 Posts
Questions and answers

Q: How is this antenna polarized?
A: If the bowtie is across (horizontal), the polarization is vertical. ie mount it with the bowtie horizontal, if it looks like an "8", you are out of polarization.

Q: I have seen others use a copper tube to feed the coaxial line through. Why don't you do that?
A: This was meant to be as simple as possible with the lowest parts count. The last thing you want to do is have to buy a 10 foot roll of copper tubing so you can make a 1" part. If you have a small copper/brass tube available, by all means use it. It might be easier than folding over the shield.

Q: Most Biquads I have seen have the reflector sides folded in. Why doesn’t yours?
A: Folding the edges over decreases the size of the vertical side lobes and increases the forward gain very slightly(~.2db). For FPV, these side lobes are a good thing to have when coming in for a landing so the edges remain straight.

Q: Aren’t you shorting out your coaxial cable with this antenna?
A: Yes… sort of. While to DC current the element might look like a short, to microwave frequencies it is actually a load.

Q: How did you verify/optimize the antenna for 50 Ohms?
A: I finally got 4NEC2’s optimizer to work (yay!)

Q: This antenna is a bit too large for me, can I use a smaller reflector?
A: Yes. You will lose some gain by doing so, but not much. Just be sure the reflector is at least as wide as your element.

Q: The copper wire seems to get bent really easily, can I use steel wire?
A: Absolutely. In fact, I recommend it if you can solder it. Metal coat hangers work well too

Q: How should I mount this antenna? Near the ground like a patch or up in the air like a Yagi or dipole?
A: It’s up to you. Experiment with it. The biquad behaves very much like a dipole, so many people will have success with it up in the air. However having reflective ground nearby will increase vertical gain slightly and limit multipath problems at the expense of the Fresnel zone.

Q: Can I feed this antenna through the side?
A: Yes. Performance will be slightly less, but it will likely not be noticed. Just be sure not to crush the center foam core insulator in the cable with the sharp 90 degree bend in the cable.

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Last edited by IBCrazy; Oct 26, 2010 at 07:54 AM.
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