[Semper Vaporo]

Putting the antenna up high is an attempt to improve the range, but that really only applies when there is something that might get in between the transmitter and the receiver... like the cuvature of the earth, or a building that has a lot of RF absorbing material in it (aluminium siding?). I can understand putting the antenna on the chimney to get the signal down around the sides of the house, but only of the train is not right against the foundation.

Another problem would be, if the transmitter only has, say 100 ft of range, and the antenna is placed on a 101 ft tower, then the signal will never reach a train on the ground. Also consider the diagonal distance from the transmitter antenna and the receiver in the train on the ground. if the base of the transmitter antenna is 99 ft from the farthest point on the railway and the antenna is 25 ft up in the air, the diagonal distance from the antenna to the train is 102.1 ft.

There is also the problem of a cable from the handheld transmitter to the antenna. Kind of defeats the purpose of a handheld. You'd need a couple hundred feet of coaxial cable so you can walk to the locomotive while still holding the controller. That miuch coax might have enough loss as to result in very little signal at the antenna end to be radiated.

 

[Semper Vaporo]

Posted By JackM on 08/11/2008 12:24 PM
I don't recall saying anything about a 100 ft. tower. It's a single-story house. And I did refer to the various angles involved (that little postscript "A square + B square = C square).
Nor did I mention "walkaround" at all. The goal in this case, at least occasionally, would be to control the train while seated with adult beverage in hand. The TV camera/transmitter would keep the engineer informed of what's going on from the 1:29 engineer's perspective. A picture leaning to one side would surely indicate a problem that needed attention.
Curvature of the earth is not the question, it's the walls of my house that might dimish the effective signal. (FYI - the Wi-Fi company I referred to does indeed want as much height as possible even though their signal will be nowhere near the 50 mile horizon.)
Anyway, I guess we've pretty well beaten this to death. When I get up and going next summer, I'll let everyone know if I make any unexpected discoveries. I do appreciate everyone's thoughts on the matter.
jack




Sorry, wasn't calling into question your expectations... merely pointing out that a tower is only of value if the curvature of the earth interferes with the communications. Some folk that might just skim this thread might tend to think that if an antenna is needed then a taller tower will cure problems, when in fact it will make things worse and they will waste money and time on trying to get the antenna higher.

As for "walkaround"... you WILL want the controller in your hand at some point in time when you are at the location of the train and not relaxing on the patio. That is the "why" of a handheld remote controller for the train! The folk using track power realized this quite early on when garden layouts went beyond the little circle of track with the power pack close at hand.

I also see that you are also considering the opposite of what I have been thinking... not only do you want radio control TO the train, but radio response FROM the train (the video system). But the same distance problems are in effect that way too. I have a 2.7MHz video camera that will transmit through the walls of my house, UNLESS "I" am standing between the two antennas! I had the receiver sitting on the VCR in the very front of the house and I took the camera out in the yard by hand. As long as I stood to the side I could get about 125-ft of range, but when I was walking away from the house with the camera (and its antenna) held in front of me, the VCR recorded very snowy pictures. When I turned to walk along the back property line it cleared up pretty good.

 

[Semper Vaporo]

I'll bow to your experience as I don't have that much myself... I only worked for Collins Radio, Inc. (now Rockwell Collins, Inc.) for 40 years, but I got out of the RF stuff abut when Art left and went on to digital avionics and computers.

But, yes getting at least one of the antennas (transmitter or receiver) away from mother earth usually helps a bit by reducing the effect of ground reflections and signal absorbtion from vegetation (broad succulent leaves absorb RF wonderfully!). But at the usual low power levels of the typical consumer R/C system, much more than twice head height adds little to the usable distance they work at.

Yet, putting the antenna on the chimney may be a good idea if it is in the middle of your layout... not the physical middle, but the point of "least-obstructions-between-transmitter-and-receiver" middle.


As for "Doesn't everybody want a stronger signal?"...

I have set the power level on my wireless router down a couple of notches. I only need enough signal to get from the dining room (where the telephone line is) to the living room (where I can sit in my easychair or the rocker with my laptop PC) and the basement shop (directly under the dining room, where I can reference the web for plans, conversion data, etc.), and I specifically do NOT want "more power" to reach my neighbor kid's bedroom (so that he can chew up my bandwidth trying to break the secure wireless encryption scheme /DesktopModules/NTForums/themes/mls/emoticons/angry.gif ).