Better range........RC + Vex

Okay, I am going to build an RC boat with vex, it is going to have a 25cc engine in it so little RC airplane servos wont do. I already have over $800 of vex and hours of experience with it. The problem is vex has very little range, is there anything I can do to increase the range?
Thanks, Brett

I can get 60-75 Feet (18.288 to 22.86 Meters) from my Transmitter to the Vex Receiver… Were you looking for more distance??

Well I figured that across the water I could get atleast 25’ more range but I would still like more range than this, I was wondering if there are any mods etc. I could do to increase range?
Thanks again, Brett

Unless you are going to illegally boost the Transmission Power of the Transmitter, you need to focus on getting the best reception at the Receiver.

Make sure the Receiver’s Antenna is up and away from the body of the boat, not parallel to any metal (especially steel). The Antenna Holder that comes with the Vex Kit is designed to hold the Antenna Wire Vertical, look in the Inventor’s Guide for how the Antenna is installed. This meets both the above criteria. Also keep the Transmitter Antenna and Receiver Antenna in the same plane, meaning that when your receiver Antenna is Vertical, the Transmitter Antenna is also Vertical…

Illegal?! I would not have thought it would be against the law to increase the transmitter power, or do you just mean against first robotics rules?

check out maxstreams XBee modules, you could probably have a buoy with the XBee module connected to a reciever and then an XBee module connected to Vex, so the remote wouldsend the signal to the bouy (those floating water things) and thenthe bouy would send the same signal back to the microcontroller

BTW xbee modules are 2.4GHz speed so this is more than fast enough
BTW2 each xbee module is about $22 dollars and youll need 2
BTW3 xbee modules send signals wirelessly with a cut and paste method, so whatevers on 1 end will be the same on the other
BTW4 each xbee module has 9 i/o pins, more than enough

I have competitively raced R/C cars and I’m also a HAM radio operator and I can tell you that most wireless controllers without any illegal modifications are good for about 100-300 feet of range. All of this is dependent on weather conditions, battery power, obstructions on and off your receiving device as well as the transmitter power. My competition radio for my cars only puts out less than 100mW and I can get about a football fields distance with it no problem, after that I can’t see it anymore. Whereas most walkie talkie style radios are limited to 1 watt or less and have a much longer range. You would have to check on the transmitter power to find out how much range you will be able to get. The higher the transmit power, the further the range.

The Animation Controller uses an XBEE Pro transmitter module that allows it to communicate with a Vex based robot with a corresponding XBEE Pro receiver module. It has a much greater range than the Vex RC and uses motion scripts and high-level robot messages to command the robot. You can see the progress that I have made using the following links:

Alright this works like magic with wifi so i don’t know if it will work with radio signals but it might.

This is a high power directional antenna that can make wifi go really really far.

I forgot to add, you need to make the antenna on the boat larger get it as high as you can.

I don’t know if this will help but you could strip some cat5 or cat5e Ethernet cable and take out the strands of wire and then coil them into an antenna and attach them to the radio receiver.

Once again i don’t know if this works with radio signals.

Here read this site and click the links:

Put a fail safe on the throttle servo. You don’t need much of a servo for that one, but on a big boat with a big engine you’d want a full size servo for the rudder. “Full Scale” I think they are called?

With 802.11b at 2Mbps and about 400mW, it got me way more than 300 feet even through half a dozen walls. Using 7dbi omni antennas too. Grab some cheap mini-pci capable routers, flash with dd-wrt and you’re on your way

the antenna for the wi-fi is constructed for 2.4 GHz i believe which is a long way from 27MHz in physical size. The wi-fi antenna is also directional which will not work for continuous R/C operation since you will lose signal when not in the beam pattern of the antenna.

to increase gain without increasing transmitter power you need to boost your antenna on either end or both if possible.
For the bot i would recommend looking into CB antennas since the CB band stops in the middle of 27mhz you should get good results stock or may need to add a small capacitor or inductor to tune it to the desired frequency to optimize it (unlikely).
the transmitter could use a directional antenna like the one you saw as long as it pointed the general direction, however instead of a little tube you would need at least 1 but really 2 loops of wire about 34 feet long. fairly impractical. So i recommend using another CB antenna only perhaps a larger one for base and smaller one on bot. this will improve range but be aware that it is important to match the antennas impedance to the output/input of the transmitter/controller or there will be power loss and you will reduce any real effects of antenna gain.

If you have old CB’s to hack you could attempt to patch your transmitter into it which will give you about 4 watts output. and possibly provide atmospheric skip which will send your signal global (which is why it would be illegal ).

i haven’t really thought about extending the range before reading your post but it’s very likely that the receiver has a pre-amp since i know by the physical size the antenna is not efficient. so if you do boost your transmit power be aware not to overpower your receiver and damage it.

Good luck with your project. If you need more information on Rf signals I highly recommend the ARRL handbook, it is one of the greatest amateur publications for R/F hobbiest, available at libraries, and will provide enough info to answer technical questions as they develop.

Vexplorer’s (AKA Vex Blue [VEX RCR]) Radios work at the 27Mhz range. Vex Red (Vex EDR) uses the 75Mhz Hobby range.

Title 47, Part 95.201 through 95.255 of the Code of Federal Regulations lists all the laws regarding Vex robots transmitters.
Basically, you can’t make any modifications to the transmitter unless certified by the FCC (good luck with that)
However, the only thing it says about antennas is “if operating from a handheld unit, the following does not apply…”
It looks like the antenna is a bit less than one quarter wavelength at the default Vex frequency (75.41 Mhz) however, creating a proper ground plane on the transmitter both would be cumbersome and likely require internal modification of the box so that’s basically out.
A larger antenna on the receiver would help as the one included is only 12 inches, but again, you really need a proper ground plane antenna and that becomes cumbersome at that frequency. I don’t know of any laws covering receivers except trying to receive ceullularphone signals (which is illegal)
And yes, I too am a ham.

I use to run RC boats and gliders back in the 80’s and the range back then was about two miles.