20Mhz Bit modification
 

So, you sick of having frequency conflicts with your buddies? Easy fix, mod your car to run on a frequency nobody else has! It's pretty simple to do, but you'll need some soldering skills. Here is the procedure:

1: Buy a 20Mhz crystal. They are less than a buck from DigiKey.com. I got mine from a junk 386 computer motherboard. (20 Mhz processor :D )

2: I replaced the 27.xxxMhz crystal in the Tx with the 20Mhz crystal.

3: Re-tune the Bit PCB for maximum range on the new frequency. This is probably the hardest part because I had to melt the wax out of the tuning coil to get the tuning tool in to turn the ferrite slug in the coil. You MUST use a plastic tool, I got mine from a local electronics store - Radio Shaft may carry them too.

You don't need to tune the transmitter because it doesn't have a LC circuit on the output stage.

Other frequencies are possible, but if you stray too far away from the cars original frequency, you'll have to modify/replace the tuning coil and/or the capacitor across the coil to re-tune the circuit.

The mod didn't increase the range any, but then again - it didn't hurt the range either! I get about 12ft. before it starts to stutter. The test mule is a LXX clone.

would the 20mhz screw up a 27mhz car?

I've had no problems with interference. The 7Mhz spacing is adequate to prevent interference. If you put the Tx antenna right next to a 27 or 35Mhz car it will control it, but the same is true with the "regular" frequencies.

Factoid: did you know that 57Mhz in in our TV frequency band here in the US? (VHF "Lo")

Did you also know that TV channels are 6Mhz apart?

Has anybody else did this with their cars?
I was thinking of making a 40 mhz car out of a 45 mhz car.

Very clever idea!

This should be in Bit Science I think.

what does Tx mean:confused:

The transmiter (controller), I believe.

I haven't tried a 40Mhz custom yet, but the 20Mhz car is still running fine. It really does come in handy when a bunch of people get together. I can always use my favorite car. Isn't 40Mhz a "legal" frequency in Australia? Anyway, re-tuning a 45Mhz Bit probably wouldn't be a problem.

I found 20MHz crystals at All Electronics with 20MHz resonators. Can you use a resonator in the car to change it's frequency?

I don't think a ceramic resonator will work.
You'll need a "real" quartz crystal for the type of oscillator that is in a Bit transmitter. The crystals are cheap enough anyway.