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 72MHz antenna for Lama or similar small heli

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Hanol

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PostSubject: 72MHz antenna for Lama or similar small heli   Mon Jun 15, 2009 5:45 pm

My 2.4GHz 4 in 1 just died and I wanted to try 72MHz receiver, so I can use my very old, but very good 72 transmitter with a bunch of adjustments. So I bought a receiver and it works fine.

However I have no idea what to to do with the receiver antenna on my heli. It supposed to be at least 1 meter long, but Lama is much smaller then that.

Can I just shorten it to 200mm or so? And if I do, how will it affect the range? I don't need a mile. Just may be 50 meters or so max. Can I safely cut it to fit inside the body?

I know they have Lamas made with 72Mhz radios. Just wander how they put the receiver antennae there. If anyone have a pix or just an explanation, I will appreciate it.
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Jack the R

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PostSubject: Re: 72MHz antenna for Lama or similar small heli   Mon Jun 15, 2009 8:27 pm

The Commanche has it wrapped in a bundle and stuffed into the nose.
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Hanol

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PostSubject: Re: 72MHz antenna for Lama or similar small heli   Mon Jun 15, 2009 9:31 pm

Jack the R wrote:
The Commanche has it wrapped in a bundle and stuffed into the nose.
What do you mean by that? Did they just stuff the whole length of the antenna wire in the nose? Again. It's NOT 2.4GHz, where you need just 5cm or so. It's 72MHz, where the the optimal antenna length is about 1 meter.
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Donnie D

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PostSubject: Re: 72MHz antenna for Lama or similar small heli   Mon Jun 15, 2009 9:47 pm

Don't cut the antenna. Best thing to do probably would be to use an antenna tube and run the wire thru the tube, then wrap it back on itself over the end of the tube. When I was flying coax helis a lot I just wound the wire around the skids. I still fly an Esky dauphin sometimes, and that antenna is coiled and stuffed into the tail section. Not the best solution, but I've never had any problems.

Donnie D smiley-happy088
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Hanol

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PostSubject: Re: 72MHz antenna for Lama or similar small heli   Mon Jun 15, 2009 10:42 pm

Donnie D wrote:
Don't cut the antenna. Best thing to do probably would be to use an antenna tube and run the wire thru the tube, then wrap it back on itself over the end of the tube. When I was flying coax helis a lot I just wound the wire around the skids. I still fly an Esky dauphin sometimes, and that antenna is coiled and stuffed into the tail section. Not the best solution, but I've never had any problems.

Donnie D smiley-happy088
In theory the optimal antenna length is the even fraction of the wave length. Like 1/1, 1/4, 1/8, etc. Full wave for 72MHz is 2.4 meters. The length used in the usual airplane models is 1.2 or 0.6 meters. Coiling will introduce some inductance, that will change the gain and change the optimal frequency. So coiling it on random can make things even worse.
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Donnie D

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PostSubject: Re: 72MHz antenna for Lama or similar small heli   Mon Jun 15, 2009 11:03 pm

Well, maybe. But I've been flying my HBFP that way for nearly 300 flights with no problems, and also flew my Belt CP the same way until I upgraded it to the DX6i. Worked for me.

Donnie D smiley-happy088
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Jack the R

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PostSubject: Re: 72MHz antenna for Lama or similar small heli   Tue Jun 16, 2009 12:54 am

My heli's are all FM, and the antenna wire comes coiled from the factory. Either around the skids (HBFP), stuff in the nose (Commanche), or left hanging (Lama v3, which I have since wrapped around the skids with no ill effect).

Just don't fly it half a mile out and you'll be fine.
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Hanol

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PostSubject: Re: 72MHz antenna for Lama or similar small heli   Tue Jun 16, 2009 1:47 am

Jack the R wrote:
My heli's are all FM, and the antenna wire comes coiled from the factory. Either around the skids (HBFP), stuff in the nose (Commanche), or left hanging (Lama v3, which I have since wrapped around the skids with no ill effect).

Just don't fly it half a mile out and you'll be fine.
I think anyone flying Lama a half mile out will set a world record :) I got the idea. Wind conditions prevented me from flying my Dauphin (Lama variant) outdoors anyway. So I am going to wrap the antenna wire around the tail, use some duct tape to hold in in place and see how it works :)
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Jack the R

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PostSubject: Re: 72MHz antenna for Lama or similar small heli   Tue Jun 16, 2009 3:20 pm

Use clear tape, it'll be less ugly.
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Hanol

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PostSubject: Re: 72MHz antenna for Lama or similar small heli   Tue Jun 16, 2009 5:11 pm

Jack the R wrote:
Use clear tape, it'll be less ugly.
Not true. I use black duct tape. If applied in a nice artistic pattern, it looks very good on the red background.
orange58
Also now you can get duct tape of all possible colors. And do you know, that it was a duct tape together with some cardboard that contributed to the safe return to Earth of Apollo-13? NEVER LEAVE HOME WITHOUT IT!!!!!! Even if you go the Moon.
orange60
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Jack the R

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PostSubject: Re: 72MHz antenna for Lama or similar small heli   Tue Jun 16, 2009 6:22 pm

Hanol wrote:
Jack the R wrote:
Use clear tape, it'll be less ugly.
Not true. I use black duct tape. If applied in a nice artistic pattern, it looks very good on the red background.

Art is my job, let's have pics and I'll critique your work orange58
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Hanol

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PostSubject: Re: 72MHz antenna for Lama or similar small heli   Tue Jun 16, 2009 6:41 pm

Jack the R wrote:
Hanol wrote:
Jack the R wrote:
Use clear tape, it'll be less ugly.
Not true. I use black duct tape. If applied in a nice artistic pattern, it looks very good on the red background.

Art is my job, let's have pics and I'll critique your work orange58

You asked for it. But if you don't like my artwork, you don't have to tell me. As a real artist, I can get very upset.
sad122
http://www.mad-russian.org/gallery/main.php?g2_itemId=1260
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