Question about transmitters and receivers.

[daveimi]

Hi

I'm ready to buy a radio and receiver and am looking the usual 2.4GHz sets, Giantcod and so on. Looking at them, some say crystal free. Does this mean some of them use crystals and some don't? If they don't use crystals how do people seperate out the channels they run on?

Thanks

Dave

[adz600]

hi dave
2.4 uses very similar technology to bluetooth in mobile phones, the transmitter and receiver lock togeather using a fixed frequency band this removes glitches, as the reciever will only answer to that transmitter. no crystals are used in any 2.4ghz sets. im new to robots but not rc my advice by good ie spektrum or futaba with built in model memory and mixing saves lots of time, jumping motors and small mixing units in the robot

[typhoon_driver]

That's correct Adam, 2.4ghz sets don't use crystals at all. This makes competitions far easier to police as there is no longer an issue with potential clashes in frequencies (big problem in ye olde days)

[terry]

The problem that might arise soon is that 2.4 has only 32 channels , maybe one day we will struggle to all get one !

[maddox10]

Means 16 machines can be activated at 1 time, as each set uses 2 channels inside the 2.4MHz band.

[terry]

Not many channels left as sometimes there is daleks,rc chairs , skele etc allready running when we are arming up.

[maddox10]

Not many channels are more than not enough.

[typhoon_driver]

Well then the 2.4 gig set simply won't work rather than allowing another transmitter to operate the machine. Hardly an issue as there are never more than 3 or 4 machines in the arena during competition fights and the large melees at the end of events etc are for fun anyways. The suprime lack of interference when compared to the old 40meg gear is also incredible. I never worry about having my aerials wrapped up and tucked in behind a fully enclosed metal container.

[daveimi]

That's great thanks. We used to have a mare at Buggy meets with crystals, iffy 27meg sets lol. As I'm getting through sorting robot out its making me look at small things like this, it's not the sort of thing I want to take chances with. I'm the most inexperienced builder-of-things and have a generally ramshackle approach. But a 13kg robot at 15mph into someones shin would be a bit sore!

[maddox10]

Featherweights have 3 kinds of allowed RX/TX systems according the FRA build rules.

40MHz Digital
459MHz Digital
2.4GHz DDS

I know what setup is the cheapest at the moment.