Lets break this one down.......
ORIGINAL: rc717
OK so I have a radio, its a MRC (here is a photo:
http://img31.imageshack.us/img31/6870/chris001v.jpg ) and the crystal on it is ch 84 75.870 MHZ. Now here is the question I have, I own to r/c vechicles, one a car and the other a boat. Can I use this same remote for both vechicles if I have the right crystals.
To answer your question quickly, yes.... Specially if you have a multi-memory radio..... but keep reading you have more problems.
The place quere it attaches is called a receiver.... If your MRC redio is compatible with an Airtronics receiver, then you are golden. If not..... you need a new radio or a new receiver. At least it seems to me that your radio and your boat receiver are on the same band 75mHz. If Airtronics and MRC are compatible, then all you have to do is get matching crystals. Sorry, I do not know if your receiver and radio are compatible... But read on.....
My r/c car is new bright I believe and its MHZ are 27.145 (Here is a photo:
http://img687.imageshack.us/img687/3218/chris005.jpg ). So can I use the same control if I just switch out the crystals when I use each vehicle. Also, does the brand of the crystals matter? Can I get any kind any put it into the control and it will work for my boat even if it is not the same company? Thanks.
Here is where it gets interesting... Your car's receiver is on the 27mHz band. No where near the 75mHz band of your radio or your boat. So for this one you definitely need a new receiver on the 75mHz band.
Now for the really interesting part. In the USA, the FCC prohibits you from changing the crystals in the radio. You can change the crystals in the receiver all day long, but not in the radio.
You have some options:
1. Get a new 2.4 system with multiple memories to be able to control your car and your boat and not loose the settings of eaither of them. Of course, you will need the radio and 2 receivers, one for your boat and one for your car. I lost one airplane (crashed total destruction) because I was cheap and tried to control 2 airplanes with a non-memory radio. One control surface was reversed, and the airplane nose dived into the ground right on take-off.
2. Find out if the Airtronics receiver is conpatible with your MRC radio. If it is, then get a receiver crystal on channel 84 (same as your radio) and go have fun. You still need a new receiver on the 75Mhz band for your car. (do I need to say that you need another receiver and crystal on channel 84 for the car?)
3. If the airtronics receiver works with your radio, and you find a crystal on channel 84, you could get an additional radio for your car on the 27mHz band. If you find one specifically on the same frequency as your receiver (27.145), then you don't have to buy additional crystals.
Bottom line, is that you need to spend some money to get them to work as you want them to...
Rafael