Conference vmszoo::rc

352.0. "R/C for a model railroad?" by RICKS::YODLOWSKI (Robert Yodlowski DTN225-4477 HLO1-1/S09 RICKS::) Mon Nov 02 1987 10:56

The model railroad club I belong to, Nashua Valley Railroad Asn, Bolton, Ma,
plans a rather unusual application of R/C equipment. We want to control the
trains on our 24'x60' HO layout by using walk around R/C transmitters feeding
stationary receivers that would be electrically interfaced to our normal
throttle controls. This would allow us to walk around our railroad freely
without a tangle of cords and has other benefits for railroad operation.

I believe I can design the required interface without much difficulty but I am
concerned with some possible problems related to the radio systems. I need
advise from you experienced R/C'ers who frequent this notes file. 

There may be cases where one transmitter is within 10' of the receivers and a
transmitter on an adjacent channel is up to 100' away. I am concerned that
the nearby transmitter will cause problems for one of the other receivers.

Do I really have something to worry about or is modern equipment so good that
there will be no problem in this situation?

What brands of equipment are most resistant to this kind of interference? Which
ones should we avoid? 

Is there anything we can do to minimize the effects of overloading? Would there
be a problem with mounting the receivers within a foot of each other and
powering them with a common power supply? 

Since we will need only 100' or less of range, are there any low power
consumption, reliable transmitter modules to which we could add our own
controls customized to railroad usage without having to pay for multiple
control sticks mounted in comparatively large boxes we won't need? Similarly
for bare receivers since we won't need servos or their decoders?

One thing we would like to avoid is poking each other with our transmitter
antennas. Can transmitters be fitted with wire antennas like the receivers?

What are currently the brand(s) of equipment you would recommend for this
application and where can I learn more about them and/or order them? 

Is there any other information I can provide that you need to help me?

Have I overlooked some other problems that might appear in this application?

Thank you for your help.

...Bob

    Here are a few suggestions:
    
    1.  Do not use aircraft frequencies!  Use surface only frequencies
    which are legal for cars, boats, or other surface vehicles.
    
    2.  You will have receiver overload interference problems if you
    get a transmitter operating on an adjacent channel much closer to
    a receiver than the transmitter on its own channel.  To avoid this
    problem, you should pick channels that are spaced further apart
    if possible.  Also, if you can locate the receivers together and
    reasonably far away from the transmitters, you will eliminate this
    problem.  A rule of thumb that I have seen is to not get the receiver
    closer to an off channel transmitter than 1/2 the distance to the
    on channel one.
    
    3.  Another type of interference that you could experience is called
    3IM.  This is caused when three equally spaced channels are operated
    with the transmitters in close proximity to each other.  To avoid
    this, pick your channels to prevent any tripletts of three equally
    spaced channels.  Otherwise, you will have problems if the transmitters
    get close together. (less than 20 feet apart)
    
    
    Charlie
    

    I would start with expermenting with a borrowed radio and check
    for interference from the mechanical noise generated by the 
    railroad equipment.  Mechanical noise can really be a problem with
    our RC equipment, and could present problems with your application,
    especially if you have long leads from the receiver to what you
    are driving.
    
    Ken

    You may want to look into the cheap rc modules on the parts shelves
    at Radio Shack.