How to change frequency on RC toy car?

Hi all. My friend and I bought 2 rc toys (1:18 scaled Ferrari F1) just for fun, but they work on same frequency (40.685 MHz) so we can't drive at same time. So i need some suggestions on how to change the frequency on one of them. The transmitter have quartz crystal, but receiver have only coil. I already tried solution "Modding Fisher-Price 72825 Formel Junior Fernlenkflitzer" found on this site, but it didn't work. I ordered quartz crystals from China working on (40.885, 40.985 and 40.285 MHz) and when i changed them in transmitter (one by one) the rc toy still reacted on commands from transmitter. Is there any other way to change frequency? Thanks in advanced.

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I wish you guys had a picture diagram of this it would help tremendous.

Jayefuu8 years ago
Changing the quartz crystal in the toy and the remote is the correct way to do it.
dule666 (author)  Jayefuu8 years ago
I know, but receiver (toy) doesn't have quartz crystal on its board. I tried changing quartz crystals in remote but car still responds to it.
zack247 dule6667 years ago
because you need to adjust the coil to the new frequency by turning the core
I'd guess the receivers aren't quartz tuned, because they aren't intended to be. Without some serious hacking you aren't going to get much further. Basically, you need a way to precisely tune the receiver to your new frequency, but the receiver has been built deliberately sloppy.
dule666 (author)  steveastrouk8 years ago
What if I try to put quartz crystal of higher frequency (45 MHz), Could i adjust receiver with adjusting a new coil?(like in "Modding Fisher-Price 72825 Formel Junior Fernlenkflitzer")
Be careful with what is legal for RC cars in your country. You must NOT interfere with any other legitimate users in your chosen band. Some frequencies are reserved for different kinds of remote control, and if you interfere with a model aircraft band you could cause a very serious accident (and it has happened)
dule666 (author)  steveastrouk8 years ago
I know all about that, most of the toys here work on 27, 40, 33, 49 MHz. I just wanted to know if I put quartz crystal (example 33 Mhz) in remote, can I adjust receiver (40 MHz) to new frequency (33 MHz) with just a coil, or i have to change more parts?
Changing the coil should work, but it might not - you won't be any worse off though ! Steve