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-   -   how long is your antenna wire? (http://www.rcuniverse.com/forum/rc-car-general-discussions-179/1619159-how-long-your-antenna-wire.html)

Piggy 03-15-2004 01:23 PM

RE: how long is your antenna wire?
 
Ok, here's the full skinny on the length of your antenna wires. In order to have the best frequency response from your antennas, you need to have what's called a quarter wavelength monopole antenna. What does this mean...a single antenna that sticks up. To optimize your antenna and reduce glitching and skittering, you need to do the following. You might want to use a calculator to assist you. But, you take 300, divide it by the frequency of your radio. This will give you the length of a single wavelength. Now, we mentioned earlier that you need a quarter wavelength. So, take the number you came up with, and divide it by 4. This will give you pretty much the exact length you need for your antenna. HOWEVER, this measurement is in meters, so you need to convert this to inches. Now, 2.5 cm equals one inch. Lets put this in better perspective.

Receiver/Transmitter frequency: 74 MHz.

300/74=4.05 meters (this one wavelength)/4=1.01 meters (quarter wavelength in meters)= 101 cm/2.5=45 inches = 3ft.9 inches

Now, there is no way that your little antenna on the car will be that long. What the manufacturers do, is bet more on the harmonic of the transmitter. I won't go into how harmonics are created, but will give you this: first harmonic for a 74 MHz transmitter is 148 MHz, 2nd is 222 MHz, 3rd is 296. So, the small antenna on your car must be a quarter wavelength of one of these harmonics. So, to have a quarter wavelength antenna for a 74 MHz transmitter, you need to have one of the following lengths (I've made it really easy for you):
3 ft. 9 Inches or 20.2 inches or 10.13 inches.

Ok, here's the really easy part. Most manufacturers design the transmitters and receivers with a certain frequency response in mind. So, if your receiver came with a 74 MHz crystal, the design for the antennas are for 74 MHz. What this means: don't cut your antenna, you're just opening up too much trouble if you do.

Hope you enjoyed your nap.

iliketobreakthings 03-15-2004 01:33 PM

RE: how long is your antenna wire?
 
Im going to buy a new antenna cause my old one broke and i lost the other piece..... does hte new antenna have to be the same length as the old one?

ericheller 03-15-2004 06:05 PM

RE: how long is your antenna wire?
 
ok heres the scoop about antenna lenghts. today i went to the hobby shop and took my brothers xxx4 because he had to go somewhere. the antenna was sorta broken so my friend there took apart the reciever and soldered on a new antenna wire. he just made it slightly longer than the antenna tube. i asked him about it and he told me that it has nothing to do with the frequency, and those of you who think it will change the frequency are morons. the antenna is just to absorb the light waves, but it does heve to be long enough or it will have poor reception and a short range.

BOOCAKE4U 03-15-2004 08:20 PM

RE: how long is your antenna wire?
 
hahaha...damn light waves!

ICrashThings 03-15-2004 08:38 PM

RE: how long is your antenna wire?
 
like i said, frequency crystal controls frequency...antenna just does range.

ericheller 03-15-2004 09:43 PM

RE: how long is your antenna wire?
 
Quote:

ORIGINAL: BOOCAKE4U

hahaha...damn light waves!
without em you wouldnt be driving your rc car, much less living.

jwren00 03-15-2004 09:45 PM

RE: how long is your antenna wire?
 
definitely not light waves though

BOOCAKE4U 03-16-2004 12:09 AM

RE: how long is your antenna wire?
 
lets just hope eric doesn't pursue a career in RF design (or optoelectronics)...

and perhaps he should learn to read and comprehend information before calling people morons, there is not one person in this thread that claimed the length of the antenna would change any frequency...

ICrashThings 03-16-2004 07:43 AM

RE: how long is your antenna wire?
 
Quote:

ORIGINAL: BOOCAKE4U

lets just hope eric doesn't pursue a career in RF design (or optoelectronics)...

and perhaps he should learn to read and comprehend information before calling people morons, there is not one person in this thread that claimed the length of the antenna would change any frequency...
but u said "antenna lengths have EVERYTHING to do with the frequency..." so what are you trying to say??

Piggy 03-16-2004 11:05 AM

RE: how long is your antenna wire?
 
[:@]I can't believe I'm replying to this thread again. Sorry, I hate to let stupid people do things that will cost them money and cause them to complain more in this forum. Ok kids, listen closely. First of all, your transmitter sends out RADIO WAVES, not light waves. Secondly, antenna length has a lot to do with frequency. Your antenna will transmit and receive a frequency determined by the crystal in your radio. However, if your antenna is too long or too short, you will transmit not just the frequency intended, but distortion as well. This means glitching and sputtering. So, leave your antenna alone and don't cut it. If need be, coil it very carefully in and around your antenna tube. But then again, don't take my word for it, it's just my job to deal in radio transmission.

claccytim 03-16-2004 12:13 PM

RE: how long is your antenna wire?
 
if the length of antenna affects the frequency transmitted, then what difference does it make what length the antenna is on the reciever? unless of course you are using a 2 way setup to communicate with your co-driver! LOL! :-):eek:

BOOCAKE4U 03-16-2004 12:52 PM

RE: how long is your antenna wire?
 
you're a good man piggy

crash - i'm not sure i can restate it any more simply but i will try...

the length of the receiver's antenna is tuned to a certain length to be able to receive a certain band or frequency...when you change that length of that antenna, you reduce the receivers ability to receive that signal...

piggys explanation before was dead-on, it all has to do with the wavelength of the actual radio signal (and its multiples)...if a given antenna is too long or too short, then it is less efficient at picking up the signal it is supposed to pick up...there are millions of man hours and thousands of books and websites devoted to the design of various types of antennae, and anyone who says the frequency of the signal to be received has nothing to do with it is totally clueless (not mentioning any names, hehe)

claccytim 03-16-2004 01:55 PM

RE: how long is your antenna wire?
 
theory or not, in practice I have coiled excess antenna and found glitching, left antenna loose and found glitching if it touches any other metal part, final resort, cut antenna ( approx 4 inches off) resut = no glitching and no decrease in range. I must be extremely lucky!

ICrashThings 03-16-2004 03:23 PM

RE: how long is your antenna wire?
 
wow this thread started with good intentions...now i just know who all the mean people are...[:o] o and by the way to make you all complain i cut my wire shorter and nothing is wrong with my trucks frequency.

royta 03-16-2004 07:00 PM

RE: RE: how long is your antenna wire?
 
Boo & Piggy are just mean. LOL. This is definitely one of the funnier posts I've read in a long time. Boo, I think these kids could benefit in purchasing a $40 CB Radio, a Wilson whip, and an SWR meter.

BOOCAKE4U 03-16-2004 07:10 PM

RE: RE: how long is your antenna wire?
 

royta 03-16-2004 07:11 PM

RE: RE: how long is your antenna wire?
 
LOL

royta 03-16-2004 07:13 PM

RE: RE: how long is your antenna wire?
 
ICRASHSTUFF (whatever). Why do you post on this board? Is it your goal to learn something? Then why in the crap do you disagree with people (boo and piggy) when they are right? You will never learn crap if you keep that up.

royta 03-16-2004 07:33 PM

RE: RE: how long is your antenna wire?
 
you too claccytim

royta 03-16-2004 07:34 PM

RE: RE: how long is your antenna wire?
 
you too ericheller

IhrtTamiya 03-16-2004 08:36 PM

RE: how long is your antenna wire?
 
well, interesting discussion. and i have a few corrections: there are 2.54 cm in an inch(simple algebra 1) and im pretty sure that transmitters arent putting out light waves. they are radio waves. why else are they called radio controlled cars?

ICrashThings 03-16-2004 09:14 PM

RE: RE: how long is your antenna wire?
 
Quote:

ORIGINAL: royta

ICRASHSTUFF (whatever). Why do you post on this board? Is it your goal to learn something? Then why in the crap do you disagree with people (boo and piggy) when they are right? You will never learn crap if you keep that up.
or you all could just answer my first question about the antenna height and be on your way, or just not post...[sm=surprised.gif]

RCFreakInFL 03-16-2004 09:36 PM

RE: RE: how long is your antenna wire?
 
wow, this thread really went to the crapper guys :(


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