I need advice on what R/C controllers other Rover-advocates have had good sucess with. The 75mhz hitech 6 channel transmitter/reciever pair just recieves too much interferance at any real distance.
What have other robot hobbiests found preferrable? Anyone like the Spektrum 5e?
Anyone play with a directional antenna to increase ranges? (I know some radio theory…and theoretically by using a directional antenna and putting all your signal in one direction, you increase the perceived wattage and signal strength in that direction.)
Since I know what direction the “Bot” will be in (North, South, East or West of me), a directional antenna to focus the wimpy wattage coming out of R/C transmitters is not a bad idea. Anyone using a directional antenna with their R/C transmitters?
What is the military using with their bombots and similar stuff? I believe they are using spreadspectrum stuff… the same stuff available in upper leval R/C cars and hobbiest robotics?
you may get better results with a 900mhz or 2.4ghz digital radio as there are more options in line with professional activities. the biggest issue as far as a hobbyist level budget is the FCC limits on transmitter power. with a 2.4GHz setup you may be able to capitalize on the boosted and directional antennas available for WLAN equipment, however 2.4GHz will have more issues with obstructions and ghosting of signals than a 900mhz system. If I recall correctly there is also a low level ammature radio license that will let you legally use higher power 900mhz equipment. again this comes with an increase in cost of course.
WRT to the military rovs… heh… I don’t think they have nearly the limits on cost or rf power or signal processing that most people are accustomed to. I would not be surprised to find some of the bigger systems have redundant systems including satellite data links.
2.4ghz systems like the Spektrum 5e have less interference than the typical 72 or 75 mhz system. However they have only 4 real analog channels. So with two used for vehicle guidance and two used for pan and tilt, there is no more analog channels for zoom of the camera lense. The other 5th channel on these are set to 1/3rd 2/3rd of servo throw when you flip the switch. I’m not aware of any spread spectrum radios with more than 4 analog channels.
I’m not particulary concerned with the fcc limits on power… I’m not looking to transmit a kilowatt, 1 or 2 watts would be plenty. I also own a legitimate private investigation business and am planning on using this device for a legitimate purpose. If push comes to shove, I can pursue the fcc licensing… but I refuse to be confined to the world of tonka toys and fisher price in regards to this devices transmission power, while our troops are overseas fighting in a country we have no business being in and bankrupting our country… but that is another topic.
Back ON topic, have either of you (or anyone else) had exposure to the commercial r/c controllers that are out there then? Something that isnt going to have more 20x more bells and whistles then I need, and preferrably won’t be xmitting on 2.4 ghz frequencies (which likely could interfere with my video xmitter)?
you might want to start with something like this which is a 915MHz ISM band module with 1W output power that supports 115KBaud data rates. You can buy the development kit on Digikey. You should probably spend some time reading their support and FAQ type information before dropping $500 but the short version is it should offer a more robust solution than hobby gear.
I was kinda of wondering what kind of range you are trying to get from your 75 mhz radio You can get up to 3000 feet (line of sight with no obstructions) and Good antennas. Some things to check
Antennas are not blocked or surrounded by metal, water or even carbon fiber. (Antennas should be out in the Breeze).
The antennas are the correct length. About 37.44 inches. (You can get loaded base antennas to use a shorter length)
The radio transmitter and the receiver are tuned correctly. If they are off frequency your range will become limited.
The receiver battery and the transmitter battery are fully charged.
One of the places that Team KISS has found good deals on radio systems. A good company that offer great service. Check them out.
Modifying aircraft radios 72 Mhz. to ground frequencies 75 Mhz.
Most of the time it is not possible to buy a radio transmitter/receiver with more than 4 channels in the 75 Mhz band. fortunately there a fellow named George Steiner at GSP products that will re-tune your receiver or transmitter for you and he does a great job. He provides quick turn around time usually two or three days days. George does not have a web page but you can call him at (916) 362-1962. He is located in Sacramento California. Make sure you call him BEFORE you make your radio purchase so he can tell you if your radio is retunable.
Thanks for all that good advice. Jim, I appreciate that… I think I’m dropping the zoom part of the equation though of my baldbot robot project. I’m going to settle for pan and tilt and a 50mm lens out of the starting gate, which i think gives me like a 10x zoom. Anyway, I did some intitial testing with that setup and am pleased with the results.
I talked to Mr. Steiner just now, boy what a great guy. Gave me some very good advice and talked about the various radios and things. I think I’m going to look at these spread spectrum csx radios he mentioned. He gave me the impression that they should work great at the distances I’m talking about (500 feet) and wasnt too concerned about it interfering with the video xmission.
Yes I am aware of twillight’s design, but 6k? His spider mite is very pretty, but I dont need pretty, I just need functional. I also know a few things in regards to the componentry we’re dealing with, and a 6k price tag is not realistic… The lynxmotion rover platform should be fine for what I’m trying to do, I had Jim upgrade the motors when I ordered and I can upgrade them again if need be. My primary issue with the rover is the communications issue between the bot and the operator. I may want an upgrade on the standard pan/tilt kit as well, but that will remain to be seen after I improve the r/c.
Just ran across the below bots. One might put one of the below bots on a more robust chassis and have most of what you need for a more reasonable price.
