Anyone know the antenner length?

[mr_lister999.]

Got this in a buggy recently. The aerail looks way to short (About 10 inches) The end looks cut so i presume it should be longer. I just dont want a car to go out range if i use it as i know it should be a set lenght (model specific) but i dont know what that is. If you have one could you measure it and give me the lenght as precicesly as you can. Thanks very much.

[netsmithUK]

there is a mathemtaical equation for this depending on the freq of the chystals for each freq the there can be several different lengths.

Unfortunately i can't remember what the equation is [8)]

I think Theo is the resident expert on this though...

[TWO STAR]

most futaba car recievers on 27 mhz antennas ranged from 12-18".the japaneese version aircraft recievers were 39".if you are worried about range,try doing a range check,make sure your transmitter antenna is fully retracted and if you can operate the reciever at 30-40 feet away you shouldnt have any problems.

[WillyChang]

Best thing is to have the wire replaced by a Futaba technician; if they know what they're doing they'll check the tuning and leave you with the optimal aerial length.

[DJTheo]

quote:Best thing is to have the wire replaced by a Futaba technician

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That aint an answer from a guy who repairs everything from his 1:1 oldtimers, over his ball bearings to his ESCs himself [8D], Willy you dissapointed me this time [][]

Optimal antenna length L (not only for RC []):

L = C / F

L = length in meters

C= speed of light = 299,792,458 m/s or easier 300,000,000 m/s

F = frequency in Hz

Aso often the calculated lenght is too big or too small, you can use also full multiples or fractions of it, for example Lx2, Lx4, or L/2, L/4, L/8, L/16, of course the smaller the worse the reception

Cheers

[netsmithUK]

Hi Theo,

I knew you knew [] Just to make it simple for the rest of us halfwits I've put a new tool online.

http://www.tamiyaclub.com/tools.asp

Thanks Theo

Cheers

Chris

[WillyChang]

quote:Originally posted by DJTheo

That aint an answer from a guy who repairs everything from his 1:1 oldtimers, over his ball bearings to his ESCs himself [8D], Willy you dissapointed me this time [][]

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Who me? []

I just grab another RX of the same make/model & band - with known intact antenna length, and copy that. [8D][8D]

But sorry, don't have any R102JE in 27Mhz.

Might be an idea too just buy a spare *black* antenna wire from Futaba. Its probably the same as the current R122JE's length. The spares come pre-cut for each freq, so just solder it and that's it.

[mr_lister999.]

I got the answer from a few club members via email. Thanks to you guys who helped.

[netsmithUK]

Did no one try my knew tool? []

http://www.tamiyaclub.com/tools.asp

[mr_lister999.]

Sweet. That is fantastic guys, well done. [^]

[netsmithUK]

cool - wouldn't want to think that i'd wasted 5 minutes of my time []

[mr_lister999.]

quote:cool - wouldn't want to think that i'd wasted 5 minutes of my time

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At least i liked it [] Just wondering: how do you access it from the home screen? I didnt see a link there.

[SJoerD]

That's because it's secret and hidden tool... []

[DJTheo]

quote:cool - wouldn't want to think that i'd wasted 5 minutes of my time

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And of mine [] [] LOL

Cheers

[malcolm]

The 'optimum length tool' (or should that be optimum tool length?)has a fatal flaw, the Receiver has a circuit at the front end that matches the actual aerial wire to the Rf stage, making it look like a full quarter or half wavelength. So the actual length is not important, just that the front end is 'tuned' to the piece of wire used.

I have 4 or 5 40 MHz receivers that have been back to the agents for service , in many cases that included fitting a new antenna, and all give good range, but all have different antenna lengths!

The best way is to buy a length of aerial wire from your LHS and fit it to the Receiver. Then do a range check. Do this by switching everything on with the transmitter aerial fully retracted. Stand in open space (like the local park) and set the model somewhere so you can see it. Leave the motor disconnected or the pinion off for safety. Now walk away while operating the steering from left to right and back. If the servo starts to go stupid before you are 50 meters away, that's not enough. If you have a pretty good range with the tx aerial folded, it will be much, much greater with it extended.

You could try different lengths of receiver wire by snipping away at the lead, as it may improve with less wire, but that's a bit hit and miss and it would be better to get it looked at by the experts.

[DJTheo]

Wavelength is a physical property like a body mass, you cant just by a circuit change the length of a wave that reaches an antenna, this sounds to me a bit as empirical excuses as often service agents are often just part replacers without knowing really what is behind [] I have heared so many pseudoscientific theories till now, could write a book with them... []

[RETRO R/C]

Wow - there are lots of tools around here !! [][] (JOKE)

Seeeeeeeeeeeeeeeeeeeeeerioously though - I respect Theo's points - as he would know...........

I never bothered with the scientific stuff - always shortened the antenna so it stuck out an inch or just over from the standard lenth antenna tube........badword - I cant see the damned thing when it's over 100 meters away anyway.........

Now my Aircraft - I NEVER TOUCH the length on them !! [xx(]

Cheers

Darryn

[WillyChang]

Funnily enough, aerial "length" to the RX is the vertical height of the wire... not the same how long it is. Folded up or broken off its the same, as is dragging on the ground when your pipe is yanked out in a smack.

Vertical because it should be the same plane as your TX aerial.

quote:Originally posted by darryn1

Now my Aircraft - I NEVER TOUCH the length on them !! [xx(]

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Now this is an interesting one... as from memory the wire on ours exited near the canopy and was pinned at back to the rudder, like a clothesline. In level flight this would mean the antenna is only about 5cm "high"... yet never had range problems.

[?]

[RETRO R/C]

LMAO Willy [^]

the aircraft is in the sky.............it needs every ounce of exposuire it can get......because it is both UP and AWAY from you.....

Cheers

Darryn

[WillyChang]

Actually its worse than that... everyone I know who flies has their TX aerial "pointing" at the plane up-there.

The signal strength around the aerial is in the shape of a cardiod ("apple", or heart-shaped rotation about the aerial=axis) so the *weakest* point of the signal propogation is the aerial's tip!! [8)]

(at which point Willy falls asleep again in Physics class)

[DJTheo]

Willy is right there, it should be mentioned that the calculated lenght doesnt need to be the total wire length but its vertical end in the "straw" or on the metal antenna.

Cheers

[RETRO R/C]

LOLOL - I wasnt arguing ??

[]

Cheers

Darryn

[WillyChang]

<willy stirs again at hint of controversy>

Anyone knows what's those "hidden" antenna jobs? Do they work??

Usually its a PCB with a zigzaggy track.

You solder the RX antenna to it, and glue that under the shell.

Had forgotten about those things until I saw Kyosho offer one as

a miniZ option. I usually run it without the pianowire eye-stabbing

thing and the range is lousy. And unlike other ESCs, the miniZ

actually pulses the motor and steering when its out of range,

most annoying.

[supergreg]

quote:Originally posted by Sjoerd

That's because it's secret and hidden tool... []

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Ok, after numerous searches through the forum for the "aerial wire calculator"-thread I now bookmarked the *secret* tool for my next attempt [8D]

Thanks to Theo for great scientific research and to Chris for wasting 5 minutes of time for coding. Great tool! [^]