Replace broken 2.4GHz transmitter antenna wire?

If you've been building electronic bits or modifying stuff you've bought then tell us all about it here. A good place to discuss the installation of 2.4GHz DIY modules too.

Re: Replace broken 2.4GHz transmitter antenna wire?

Postby JMP_blackfoot » Wed Mar 02, 2011 1:56 am

Based on some tests I did a while back with Flysky receivers, I would think you'll find that 27 to 30 mm will be good.
26 mm and under definitely reduce the range.
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Re: Replace broken 2.4GHz transmitter antenna wire?

Postby JensR » Wed Mar 02, 2011 1:59 pm

Thanks! That's good to know, I will approach the decisive length with care.
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Re: Replace broken 2.4GHz transmitter antenna wire?

Postby Flash1940 » Wed Mar 02, 2011 8:15 pm

In the world of amateur radio....the accepted calculation method for a half wave antenna in free space is L = 468/f....where f is in Mhz. The length would come out in feet for a center-fed dipole antenna. So by dinking around with the numbers & stuff you will end up with a calculation resulting in 1.17 inches for a 1/4 wave antenna....or for you guys down under....29.718 mm. Whoever that was that said 27 to 30 mm is right on the mark. Personally....I wouldn't cut it shorter than 29 mm.
For a 5/8 wave antenna.....my calculations give 2.925 inches....or 74.295 mm.
Anybody agree or disagree???? What do you think Bruce???? I'm sure we will all accept your figures.
Over the weekend I measured the two whiskers on the V8 receiver. If you will notice the antenna is made up of the coaxial cable used on their other equipment. This coax is really tiny stuff. I have no information on it....impedance.....velocity factor.....loss/1000 ft.....nothing ! Anyway.....the whiskers both measured 1.3125" or 32.16mm. This seems a bit long.....or cut for a frequency a bit lower than 2.4 Ghz. I'm guessing that the length of the whole antenna stub is configured to be a good match to the input impedance of the receiver's first stage.

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Re: Replace broken 2.4GHz transmitter antenna wire?

Postby JensR » Sat Mar 12, 2011 2:58 pm

Thanks everyone for your help.
Over the last days, I prepared my modified twin-9x and also prepared the broken wire as suggested, stripping the outer insulation and mesh for about 30mm. Last night, I assembled everything and, while I have not yet done a full range check, it seems that it works very well. As I really need to be close to that machine, I do not envision any problems. If my next model needs a longer range, I "maybe perhaps might" have to do something about it. ;)

Thanks again
Jens
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Re: Replace broken 2.4GHz transmitter antenna wire?

Postby JensR » Mon Mar 14, 2011 2:42 pm

Dear all,

on Sunday, I was out on the beach with my contraption and it worked very nicely. Range is by far enough: When the batteries were two-thirds empty, range was still at the very least 10 or 15m - I didn't test any further distances. Would anyone be interested in such a test with the shortened antenna? I might need a helper, though :D

Here it is:
Image
Image
link to flickr:
http://www.flickr.com/photos/22070130@N07/5526362522/

And here's a video of the whole machine, for those interested:
http://www.flickr.com/photos/22070130@N07/5524641117/

Cheers
Jens
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