Post by thread:[OT] anyone experianced with model RC Xmit & rec.

I have very limited knowledge of transmitters and receiver. We have a little remote device that we want to control underwater about 300 ft 100M.. Rater then re invent the wheel so to speak. If we could use one of these radio control sets that we have we would have75% of the project done. Here is the question: If we ran a wire from the transmitter antenna through an air line that has to go to the underwater unit and connected it to the receiver antenna, would that work? Recon

On 4/13/07, Recon <spam_OUT556reconTakeThisOuTcharter.net> wrote: > > > If we ran a wire from the transmitter antenna through an air line that > has to go to the underwater unit and connected it to the receiver > antenna, would that work? > Did the laws of physics suddenly change and RF suddenly stop passing through water? Nate

David VanHorn wrote: >>>If we ran a wire from the transmitter antenna through an air line that >>>has to go to the underwater unit and connected it to the receiver >>>antenna, would that work? > > > You'd actually have to attenuate the signal significantly, and it > would be best to use shielded cable, but YES, this will work. Actually, it would depend on the kind of water (fresh vs salt), and on the radio frequency in use. Salt water, and high frequency (2.4Ghz is now used in many sets) and you won't get far, even with a wire. I doubt that you can do 300M even at 72Mhz (common R/C band in the US) with just a bare wire. The loading from salt water is HUGE. I would suggest using COAX so that you have a controlled impedance path to the receiver, and then yes, it will work. But I agree that you will probably need an antenuator to not overload the RX. If you need it thin, RG174 coax is about 1/8" diameter and not too lossy at 72Mhz. Robert

Robert Rolf wrote: {Quote hidden}>>>>If we ran a wire from the transmitter antenna through an air line that >>>>has to go to the underwater unit and connected it to the receiver >>>>antenna, would that work? >> >> >> You'd actually have to attenuate the signal significantly, and it >> would be best to use shielded cable, but YES, this will work. > > Actually, it would depend on the kind of water (fresh vs salt), > and on the radio frequency in use. > Salt water, and high frequency (2.4Ghz is now used in many sets) > and you won't get far, even with a wire. I doubt that you can do > 300M even at 72Mhz (common R/C band in the US) with just a bare wire. > The loading from salt water is HUGE. > > I would suggest using COAX so that you have a controlled impedance path > to the receiver, and then yes, it will work. But I agree that you will > probably need an antenuator to not overload the RX. > If you need it thin, RG174 coax is about 1/8" diameter and not too lossy > at 72Mhz. If the OP is willing to run coax... why bother with RF at all? Why not run a well insulated cable with however many pairs the OP needs to control this thing? Perhaps we need to better understand the application? Vitaliy

<snip> > >If the OP is willing to run coax... why bother with RF at all? Why not run a >well insulated cable with however many pairs the OP needs to control this >thing? > >Perhaps we need to better understand the application? > >Vitaliy > > This is just a small remote piloted camera housing that I am helping my son and grandson build as a hobby project. We are trying to do it on a low budget. If we had $6,000 USD we could go out and buy a used one. all the waterproof cable that has12 or more conductors has the following disadvantages: Cost, weight, size and flexability. And then we would have to design purchase and build circuits to replace everything that is already done in an existing Radio control system that we already have. RECON

On Apr 14, 2007, at 8:37 AM, Recon wrote: >> If the OP is willing to run coax... why bother with RF at all? >> Why not run a well insulated cable with however many pairs the >> OP needs to control this thing? >> Presumably (and now confirmed) because standard RC gear works over RF. Which brings up an interesting question. Are there any standard ways of running typical RC signaling over wire? At the basic level it's a relatively simple serial datastream and (for example) the micro RC people have had an easy time modulating infrared instead of radio. As-is, it's probably not ideal for sending over a twisted pair, but there's probably a relatively simple scheme that would work. I'd think there would be a fair number of places where one might want to use standard ("user-optimized") RC control gear in RF-unfriendly environments... BillW

> This is just a small remote piloted camera housing that I am helping > my > son and grandson build as a hobby project. We are trying to do it on > a > low budget. If we had $6,000 USD we could go out and buy a used > one. >From what I've seen so far ... This should work OK at moderate distances using a single pair of wires with ground on one wire and signal on the other. Actually attempting to match to it as an unbalanced transmission line may help, but chances are just connecting directly would work. As someone mentioned, attenuation (2 resistors) may be needed.) However, you MAY be able to get a more consistently workable result by feeding and receiving the modulation signal that is used to drive the transmitter. This does take more effort than just using the tx/rx directly. The transmitter will be "keyed" by a signal, quite probably at 5 volts, and this signal will be reconstituted by the receiver. Eliminating the RF "middleman" allows you to use a single pair at pulse rates in the (probably) 10's of kbps range and eliminates RF considerations. If I was in your position I try it with the 1 wire and a pair of wires with RF to see what happens and go from there. Odds are you can get enough signal by wrapping a few turns of an insulated wire around the tx antenna or similar fairly "loose" coupling. You talk about RC control but say its controlling a camera. If there is a returned video signal (maybe there isn't) then it's going to get more complex but a wire pair solution and RF should still be able to be made to work over moderate distances. Russell

I have been using Futaba R/C products since about 1991. I have been using a 9ZAPS for RC airplanes since about 1995. It (and many others) use a pluggable RF module. You can access the encoder input to the rf deck at that point. Older 9Z's should be available for $200 or less. There are new products with similar modules and about the same price. The going rate for transmitter/receivers that are AM are available at swap meets for about $35. John Ferrell W8CCW "Life is easier if you learn to plow around the stumps" http://DixieNC.US {Original Message removed}

I'm using Hitec, which uses the same principles as Futaba - actually it is a kind of Futaba clone. It should not be too hard to use just that RF module without the controller, however, I am not sure how the controller tells to the module to use PCM encodings instead PPM (you can select in between them using the controller's menu). Anyway, you can also use the buddy box connector to feed the transmitter with your input (PPM), the only thing you need to change is that originally if you release the trainer switch you will get back the control from the buddy box to the instructor's controller. All you need to do that is to replace that switch not to do that and then let your original, virtually untouched controller to do the rest. Tamas On 4/16/07, John Ferrell <.....johnferrellKILLspam@spam@earthlink.net> wrote: {Quote hidden}> > I have been using Futaba R/C products since about 1991. I have been using > a > 9ZAPS for RC airplanes since about 1995. It (and many others) use a > pluggable RF module. You can access the encoder input to the rf deck at > that > point. > > Older 9Z's should be available for $200 or less. There are new products > with > similar modules and about the same price. > > The going rate for transmitter/receivers that are AM are available at swap > meets for about $35. > > John Ferrell W8CCW > "Life is easier if you learn to plow > around the stumps" > http://DixieNC.US > > {Original Message removed}