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Old Nov 11, 2010, 02:22 PM
Engineer for Christ
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For an R/C truck, you would be best suited with 3/2 wave dipoles on both the truck and RX. A ground plane antenna on the truck would work fairly well, but the 3/2 wave dipole would likely work better.

-Alex
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Old Nov 23, 2010, 06:29 AM
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Greece, Central Macedonia, Thessalonika
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Hi Alex,
Thank you for the effort you make to educate and inspire us all. Your home build solutions are great!
Can you please clarify, when you say to mount the antenna 1-2 meters high, do you mean with only air (or non-metallic materials) between it and the ground? I usually place mt VRx on the roof of my car with antenna pointing upwards, but I am getting only 1200m range from my 800mW 1.2GHz system on stock antennas. I have build your dipole and a GPP, but before I test the range with the custom made antennas, I want to know if my VRx placement is fundamentally wrong.
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Old Nov 23, 2010, 07:28 AM
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Quote:
Originally Posted by sfakias View Post
Hi Alex,
Thank you for the effort you make to educate and inspire us all. Your home build solutions are great!
Can you please clarify, when you say to mount the antenna 1-2 meters high, do you mean with only air (or non-metallic materials) between it and the ground? I usually place mt VRx on the roof of my car with antenna pointing upwards, but I am getting only 1200m range from my 800mW 1.2GHz system on stock antennas. I have build your dipole and a GPP, but before I test the range with the custom made antennas, I want to know if my VRx placement is fundamentally wrong.
Yes. Ideally you would place it a few meters in the air with only non condictive materials in between when possible. I actually mount my ground plane antenna on a wooden stick attached to my video goggles and tet it rest a few inches over my head. The reason is to mitigate multipath interference. The ground plane antenna will work fine on the roof of the car, but could cause some multipath disturbance.

Mounting the patch on the roof is ok. Personally, I prefer it to be on the ground where possible, but have had good results with one on the roof or trunk of the car.

-Alex
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Old Nov 26, 2010, 07:23 AM
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Can I use RG-174/U for coaxial type?
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Old Nov 26, 2010, 07:35 AM
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Yes, that will work fine.
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Old Dec 23, 2010, 09:47 AM
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Hello, thank's for this "how to do".

I would like to know if 1/2 or full wave lenth will give more gain. Plan to make this antenna for 1280mhz.

Thank's
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Old Dec 23, 2010, 05:28 PM
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Full wavelengths are bad due to high impedance, but odd multiples of 1/2 are fine. 3/2 or 5/2 wave would do well to increase gain.

-Alex
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Old Dec 26, 2010, 10:59 AM
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Slovenia
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Quote:
Originally Posted by IBCrazy View Post
Adjusting the antenna:

While many of these usually have the radiator 90 degrees from the ground plane, in many cases a slightly greater angle is desirable. As the angle opens up, the gain drops and directs the pattern more outward. I find that 100-120 degrees is most desirable. This allows me to have the antenna mounted on a not flat surface as well as gives me a bit better low altitude resolution.

If you have a Quadcopter, this antenna will do very well if mounted upsidedown with a 120 degree angle on the elements.

-Alex
Hi Alex im making this antenna for my Mikrocopter. Do you mean 120 degrees between central element and legs...
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Old Dec 27, 2010, 08:49 AM
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That picture is correct, yes.
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Old Jan 06, 2011, 02:34 PM
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United States, NC, Charlotte
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Sick at home today, so I built one. My stock BOB 1.280 omni sucks, and my rcam dipole was worse so I must have messed up. So heres another go!
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Old Jan 17, 2011, 04:23 PM
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Spending more quality time with the soldering iron.

Alex, you said that full wave is no good due to impedence, but odd half-wave mulitiples are okay. Does that include 1/2, or just 3/2, 5/2, 7/2, etc?

kendall
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Old Jan 17, 2011, 09:36 PM
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All work well up to 9/2 wave. Beyond 9/2 wave the antenna efficiency is degraded significantly.
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Old Jan 18, 2011, 06:02 PM
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Is there any advantage to increasing the number of ground elements? More uniform radiation pattern maybe?

kendall
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Old Jan 18, 2011, 07:48 PM
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Can this antenna be used as a TX one too ?
Is it better than the dipole for a glider if so ?
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Old Jan 18, 2011, 09:03 PM
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Here's mine--half-wave, 910MHz, 120-degrees, RG-58. I did a slight mod of the coax type by first soldering the ground elements to a short length of brass tubing. Then I stripped the cable, folded the shield back over the jacket, slipped the brass tubing over until the point where the shield folded over was even with where the ground elements were soldered and crimped the brass tubing. The nylon cone is there to reinforce the solder joint between the active element and the core of the cable.

See any problems?

Need flying/field trial weather.

kendall
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