Antenna wire length - RC Groups
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May 22, 2012, 03:00 AM
Registered User
rcmaverick's Avatar
Discussion

Antenna wire length


What is the length of antenna wire needed for a 2.4 ghz Tx/Rx ? Orange receivers come with a very short antenna. It seems to work fine and range checked but wanted to make sure.
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May 22, 2012, 03:28 AM
Registered User
2.4GHz antennae are very short. Usually they're about 6" of plastic-coated wire with about 2" of what looks like bare wire at the end. The bare wire at the end is the actual antenna, and you mustn't alter its length.
May 22, 2012, 03:42 AM
Registered User
DeeBee1's Avatar
I'm sure someone will explain this better than I can, but I think that the length of any antenna is more to do with a multiple of the wavelength being received, rather than the actual total amount of wire.

So 72MHz antennae need to be a certain length to work properly and likewise 2.4GHz antennae will be shorter, because they operate at a shorter wavelength. If you stuck a random extra amount of length on an antenna, it might actually perform worse, even though it's longer.
May 22, 2012, 04:06 AM
God of Gravity Poisoning
Arkansas Travelr's Avatar
To the best of my knowledge 2.4 systems don't use a wire antenna it is micro coaxial cable that plugs into the rx they can't be easily repaired nor can they be replaced with regular wire, you need a real antenna.
May 22, 2012, 07:39 AM
Registered User
The 2.4GHz antenna is a coaxial (wire within a wire) for the first bit, which doesn't actually receive the signal, then is a simple wire for the bit sticking out the end, which does receive the signal. It's quite easy to replace, if you have the correct coaxial cable.

Yes, DeeBee1, the antenna length is a fraction of the wavelength for best efficiency, so adding more to it will make it worse, unless (maybe) you go all the way to the next fraction (like from 1/2 to full-size).
May 22, 2012, 10:04 AM
Registered User
As stated above, the antenna for 2.4GHz is only the last 28mm (the bared end) .of the cable comming off the receiver. The length between this antenna and the receiver PC board can vary between brands and use ; zero on some and several inches or cms on others. This cable needs to be treated with some care as any crimping or deformation of it can adversely effect the signal strength as seen by the receiver. Any changes of the length of this bared end need to be done in odd multiples of 1/4 the wavelength to avoid degredation of the received signal.
May 23, 2012, 07:00 PM
That's a funny word
What about the TX? I had a similar question regarding using a different TX aerial with another brands module that never got answered on another forum. I hope the OP don't mind.

My specific question was about using the Turnigy 9x aerial on the anylink module.

I see that the anylink antenna is larger , but much shorter than the turnigy. Here's the questions.

1. Can I solder the longer Turnigy antenna (without reduced range or other problem) to the tactic module even though it is longer? It would make it look nice and factory and the module would fit in the stock location with the stock turnigy antenna.
2. Is there 2 solder connections on each antenna? It kinda looks like it is a two connection deal. OR is it just a simple single wire like my old AM rx antennas?
3. Another option is to use the tactic short antenna wire up thru the turnigy TX housing , but it would fall very short and just barely come out the top of the TX. It would be much shorter than it's housing.
4. Is the diameter of the ant important? The tactic one looks like it is fatter wire or maybe more insulation? Is there a wire and shield (like coax cable)
May 23, 2012, 07:18 PM
Dude, I do fly all day long!
rcalldaylong's Avatar
Quote:
Originally Posted by Arkansas Travelr
To the best of my knowledge 2.4 systems don't use a wire antenna it is micro coaxial cable that plugs into the rx they can't be easily repaired nor can they be replaced with regular wire, you need a real antenna.
Not true. While what you've said is the optimal antenna for 2.4, some 2.4 rx uses a simple wire. I know for sure the orange 6ch from HK is a simple wire.

I've even toyed with the idea of replacing the antenna with a longer one. In some instances I get better range, and in some, no change or worst.

https://www.rcgroups.com/forums/show...postcount=1243
May 24, 2012, 12:38 AM
Registered User
HELModels's Avatar
There's good info in this thread, thanks. So, that little bit of exposed antenna is the important part. I dont need to worry about how the whole wire is oriented, just put both business ends in different areas if I have two antennae?
May 24, 2012, 12:56 AM
Dude, I do fly all day long!
rcalldaylong's Avatar
Quote:
Originally Posted by HELModels
There's good info in this thread, thanks. So, that little bit of exposed antenna is the important part. I dont need to worry about how the whole wire is oriented, just put both business ends in different areas if I have two antennae?
Yea. something like that.

take a look at this and see if it helps.
At one point I read all of it and understood it...now a days, I just fly and I don't worry too much. Haven't had a glitch yet.

http://www.spektrumrc.com/DSM/Techno...dFeatures.aspx
May 24, 2012, 03:11 AM
Registered User
Quote:
Originally Posted by HELModels
There's good info in this thread, thanks. So, that little bit of exposed antenna is the important part. I dont need to worry about how the whole wire is oriented, just put both business ends in different areas if I have two antennae?
In different locations and, ideally, at 90 degrees to each other so that they get optimum reception whichever way you model is facing.
May 24, 2012, 04:22 AM
christian theme park operator
H2SO4's Avatar
velocity = frequency * wavelength

In this case the velocity is C, at say 300,000,000 metres per second. The frequency is 2.4GHz, or 2,400,000,000 Hertz. Dividing the first big number by the second yields a wavelength of 0.125 metres, or 12.5cm. Since we're using quarter-wave antennae, that works out at just over 31mm.

The point of the coax is to stop some parts of the cable from acting like an antenna - the bits covered by the outer sheath. Because the last 31mm is exposed (hopefully ), that becomes the active portion. OrangeRx receivers don't use coax because they've got 31mm worth of wire soldered directly to the circuit board, and hence their antenna cannot be relocated within the distance permitted by the length of coax, as provided with FrSky receivers for example.
May 24, 2012, 08:18 PM
ShopCzar
Endlesslag's Avatar
So if you had a damaged coax antenna, could you cut off the place where it got cut/torn/etc and then strip 31mm of the shielding off and basically have a working antenna again?
If so...I might be able to save a damaged rx
May 24, 2012, 10:49 PM
christian theme park operator
H2SO4's Avatar
Quote:
Originally Posted by Endlesslag
So if you had a damaged coax antenna, could you cut off the place where it got cut/torn/etc and then strip 31mm of the shielding off and basically have a working antenna again?
If so...I might be able to save a damaged rx
Yes. There's nothing magical about the length of the shielded portion. The only thing that matters is that the exposed section (without shielding) should correspond to the wavelength.

A range-check afterwards would be a good idea, of course.
May 24, 2012, 10:53 PM
ShopCzar
Endlesslag's Avatar
Quote:
Originally Posted by H2SO4
Yes. There's nothing magical about the length of the shielded portion. The only thing that matters is that the exposed section (without shielding) should correspond to the wavelength.

A range-check afterwards would be a good idea, of course.
Cool, thought so. I guess tomorrow I'll get out the wire strippers and calipers
I should be able to save an AR500 and a flysky car rx now! Learn something new every day


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