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Old Sep 18, 2004, 08:26 AM
Bubble Head SSN 762
LexTalionis's Avatar
Austin Bergstrom, Texas, United States
Joined Apr 2004
1,347 Posts
Range problems with my 4-yr old Son's 27mhz AM RTF...

Hi all,

I got my 4 year old son an RTF 27mhz AM airplane (really cheap, but that's the point). I want to get him started early.

The range is only about 30ft before the engines start to sputter. I've checked the RX/ESC combo and the antenna connections looks good and the TX batteries are topped off. The Nimh pack is topped off too. Since I can't return this (bought a year ago), I was wondering if I could electrically lenghten the antenna by putting a coil of wire in series with the antenna.

The 27mhz AM antenna is, by default, 18 inches on this plane. Is this long enough? Any suggestions here would be great. Thanks!
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Old Sep 18, 2004, 09:44 AM
Electric since 1990
Foamaholic's Avatar
East Central Ohio, United States
Joined Jun 2004
3,736 Posts
You could experiment with antenna length, but it's only likely to shorten range futher. The problem with 27 mhz is that it can pick up all kinds of stray signals. See how the range is in a different location. How is the antenna routed? Keep it away from other electronics, receiver, servos, etc. and make it as straight as possible.
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Old Sep 18, 2004, 09:57 AM
God is good
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Banjul
Joined Jan 2001
4,246 Posts
The 27 Mhz tx's are designed to have a low range.
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Old Sep 18, 2004, 10:08 AM
Bubble Head SSN 762
LexTalionis's Avatar
Austin Bergstrom, Texas, United States
Joined Apr 2004
1,347 Posts
Designed for low range...hummm...30ft is pretty low. There are no servos in this one...dual engines left/right is accomplished via the motors.

I'll try to lengthen it a bit. Thanks!

Lex
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Old Sep 18, 2004, 11:17 AM
Around the World
cadconversions's Avatar
Scottsville, KY
Joined Jun 2002
5,641 Posts
I had a "Wal-mart" special car when I was younger on 27 Mhz... 30 feet was about max. The 49 Mhz is a little better.
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Old Sep 18, 2004, 11:26 AM
Bubble Head SSN 762
LexTalionis's Avatar
Austin Bergstrom, Texas, United States
Joined Apr 2004
1,347 Posts
Humm...we'll I now know the general range of 27mhz AM...thanks guys!

Lex
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Old Sep 18, 2004, 11:57 AM
Big 3D
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Lufkin, TX
Joined Feb 2003
874 Posts
which plane is it?
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Old Sep 18, 2004, 12:17 PM
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Mark Wood's Avatar
United States, CA, Bear Valley Springs
Joined Feb 2000
26,416 Posts
Lengthening won't do anything. I'm not sure what the proper length for a 27mhz antenna bit it is specific.

mw
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Old Sep 18, 2004, 05:08 PM
Bubble Head SSN 762
LexTalionis's Avatar
Austin Bergstrom, Texas, United States
Joined Apr 2004
1,347 Posts
I don't remember the name of it, but it was bought at Wal-Mart about a year ago and it was a flimsy Delta type wing with two small (about have the size of IPS motors) in the center of each wing half. It was yellow and black. I've taken the motors out and esc/rx out and put them on a small 25" foam glider and it flys fine if the motors would stay on past 30ft...after about 30ft the motors loose signal and begin to cut out because of range issues. I'll try a coil and call it then and just have an on/off switch for the motors and just have my boy fly it w/o r/c, at least then it would fly futher...just don't know where to ;-)

Thanks,
Lex
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Old Sep 18, 2004, 07:44 PM
Big 3D
jamin's Avatar
Lufkin, TX
Joined Feb 2003
874 Posts
The prob is most likly not the RX but the TX. Try adding another cell to it. The guys in indoor forum have gotten improved range on the Bit charger type cars like this.

I also read somewhere about hanging a copper wire the same length as the ant. from the neg battery connection. Not sure on this but is cheap to try.
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Old Sep 18, 2004, 08:04 PM
Bubble Head SSN 762
LexTalionis's Avatar
Austin Bergstrom, Texas, United States
Joined Apr 2004
1,347 Posts
Well, I just added a coil made from 30awg magnet wire in series with the antenna and the range improved about 4 fold. I have thought about the TX since it's only 6 AA cells.

copper wire from the neg battery connection????? just slap a wire the same length to any neg terminal in the battery compartment and try? sound like pfm to me if it does work. I'll give it a try too.

Thanks,
Lex
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Old Sep 23, 2004, 04:49 PM
Registered User
Dublin, Ireland
Joined Mar 2002
452 Posts
The length of the antenna is a tuned feature.
if you are planning to lengthen it, it would be best to double the length, instead of adding e.g.50% extra as the tuning is less interfered with .
Also the transmitter is low power compared to the usual equipment used by model flyers. So the Tx is limiting range also, but more difficult to improve.
It would be wise to check out insurance considerations if you are using 27AM in a built up area, because FM is considered a minimum standard for safety in most countries. FM is of course more interference resistant.
In any case you will probably find that interference mostly comes from within your own model, and reducing throtle is very effective at reducing interference, and thus increasing effective range.
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Old Sep 24, 2004, 03:40 PM
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United Kingdom, Slough
Joined Aug 2003
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Adding an equal length wire to the -ve terminal can improve the radiation from the antenna. When you hold the transmitter, you actually become part of the circuit. The whip antenna forms one part of the dipole, and you become the other half. If the intercapacitance between you and the groundplane in the transmitter is poor, then it becomes effectively a lopsided dipole. Hence the addition of the wire to the -ve side, this makes the set see a full dipole.


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Old Sep 24, 2004, 03:51 PM
Bubble Head SSN 762
LexTalionis's Avatar
Austin Bergstrom, Texas, United States
Joined Apr 2004
1,347 Posts
mac_man,

Could you please describe this in more general terms? How long of a piece of wire should I connect to one of the negative battery terminals and where should the other end connect to?

Thanks,
Lex
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Old Sep 24, 2004, 03:57 PM
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United Kingdom, Slough
Joined Aug 2003
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The way I do it, is to cut a length of wire the same as the extended transmit antenna. If you have a charge socket on the side of the transmitter, the obtain a plug to fit and solder one end of the wire to the -ve side of the connector. The other end just dangles loose, you could weight it with anything non-metallic.
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