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KeithLuneau

Antenna Length

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I was just wondering about the length of the antenna on my video transmitter. Right now I've got it at 1/4 wave length, what would happen if I were to put a longer one on, say half or full wave length? Would there be an increase in range?

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I suspect you will see a slight gain in range with a 1/2 wave aerial. At full wave, I predict less range (but YMMV).

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So in theory, and according to the figures on the HK project page, if I were to replace my 123mm antenna with a 246mm one, I might see a slight gain in performance? I might have to try that soon. I'll be sure to post the results if and when I do. Thanks!

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if I were to replace my 123mm antenna with a 246mm one, I might see a slight gain in performance?

Assuming you have a typical "1.2Ghz" Hong Kong'ish Tx, I'll assume it is at ~1.16Ghz. That would suggest a 1/4 wave element length of 61.5mm. A simple 1/2 wave whip solution would be double that.

Here's an idea: I suggest you rescale Yb2normal's ground plane aerial for 1.16Ghz and try it instead.

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From my experience, you might see a little bit of improvement, but if you're looking for a performance increase, I'd look at other losses in your system. Oftentimes adding a good ground plane to your antenna and using low loss connectors (even better is directly soldering the coax to the antenna/xmitter/reciever...elimitating the connectors entierly) can boost your signal strength substantially.

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Seems I'm already using a half wave antenna then, I guess my calculations were off... :)

I just gave the ground plane a once over, and might just try that. I'm guessing I coulg make the elements each 61.5mm for a 1/4 wave ground plane?

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Got another question...

I've read a little about ground plane antennas, and a couple of websites said that it's best to mount them as far away from wires and conductive materials as possible. The airplane I'm mounting this on uses an aluminum fuselage from a Slow Stick. The only good way to mount it is to this aluminum square tubing. Will this have a large effect on the antenna? Would I be better off sticking with the regular whip?

Also, what about the receiver on my plane? Right now it's mounted almost directly above the antenna. Will that have an effect on it?

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The only good way to mount it is to this aluminum square tubing. Will this have a large effect on the antenna?

I doubt you will notice any effect at all.

Also, what about the receiver on my plane? Right now it's mounted almost directly above the antenna. Will that have an effect on it?

You may experience R/C interference or reduced range. Don't mount the R/C Rx or its antenna close to the video gear.

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Thanks for the help! I've made up the antenna and soldered it directly to the PCB for my transmitter. I hope to be abot to try it out tomorrow, weather permitting of course!

About the R/C receiver... I've flown it a couple of times with the transmitter mounted close to the R/C receiver without problems. I chose to use a full sized dual conversion receiver in this plane just to be on the safe side. Even still, I shuffled things around and moved the receiver a few more inches away, and mounted the video transmitter a little lower than it was instead of directly to the fuselage, so that helps.

I'll be sure to post my findings after getting a flight in with the new antenna!

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For the record I tryed this with 2.4Ghz gear and there was no measurable increase in gain.

I tryed 3/4 wave as this should give a good match and in testing it did but still no gain. I dont know why but I have given up that route now.

Terry

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