# attaching an antenna



## lownote (Jan 3, 2008)

I have four Aristo 75 mhz receivers and they all came with different length antennas. One is very long, about three times the length of my Mikado's boiler. The others are considerably shorter. The longest one seems to give me the best range. It's taped the the inside of the Mikado boiler shell. 

The other two (I have a 4th awaiting installation in a Thomas the tank engine I'm making for my daughter) are maybe 1/3d that length, and I seem to get better range when I run them outside the boiler shell. You can see the antenna twisted along the handrail in the photo below. 

First, am I wrong to think that it would matter if the antenna is inside or outside the shell? 

Second, is there a better way to do this? I thought of gluing the antenna to the handrail, or maybe stripping the insulation from the antenna and soldering it to the handrail. Maybe I should just tape it to the inside of the boiler? 

I have a Bachmann "annie" to which I did the same thing--ran the antenna along the handrail 

I should note that range is not a huge problem, I have a small layout and it's generally fine. Sometimes I have to extend the antenna on the TE transmitter, but otherwise it's fine


----------



## Semper Vaporo (Jan 2, 2008)

Antennas "should" be a particular length for the frequency it is designed to receive. Some antennas maybe shorter because there is basically a coil of wire at the bottom that makes up for the length it should be. 

If the antenna is just cut to be shorter it won't work as well (reduced distance reception) as one of the proper length. Putting the coil of wire at the base improves the effeciency of the antenna but does not make it as good as one of the proper length. 

You are right that you really don't want to bury the antenna inside a metal shell. This will attenuate the signal from the transmitter, maybe to the point that it cannot be picked up at all. 

Ideally, the antenna should be away from anything metal and oriented in the same position as the transmiting antenna (polarized the same way)... if you hold your transmitter so the antenna is perfectly verticle then the receiver should be the same. If you hold your transmitter so the antenna is horizontal then so should you receiver antenna... BUT!!!! your train is probably going to be going around in some sort of circle and this means that at some point it the receiver antenna will not be parallel to the transmitter antenna and you will lose some signal... so verticle is the "best" (that is, unless your train goes up and down some realy steep hills!/DesktopModules/NTForums/themes/mls/emoticons/shocked.gif). 

Most people wind the antenna wire around a piece of cardboard or plastic and set it inside of something that is not metal (or has little metal or at least some open "window" of some sort to let the radio signal reach the antenna. 

Winding the antenna into a tight coil is not a good idea, but a loose coil is okay... at least the coil will cause at least some part of the antenna to be kinda parallel to the transmitter antenna no matter which way the train is going or is oriented to the transmitter. 

Ideally, the transmitter and receiver antennas are the same, and proper, length and kept parallel. But the real world sometimes makes that hard to do, so base loading is used to shorten the antennas, and they can be coiled a bit and you attempt to hide them a wee bit, but each compromise in the ideal means you loose some distance that they will work over. If you can control your train on your layout, then whatever you have is good enough. 

"IF" you had control over the power level of the transmitter (I know of no commercially available transmitters that you can do so), you could save battery power if the antennas were "ideal", but since you cannot control the power level you get a transmitter and fiddle with the antennas to try to make it work.


----------



## Bill Swindell (Jan 2, 2008)

Take a look at the following site... 

http://www.ecubedrc.com/antennas.htm 

They have 75mhz antennas that are only about 6" long.


----------

