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]

Re: Question about transmitters and receivers.

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]

Re: Question about transmitters and receivers.

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]

Re: Question about transmitters and receivers.

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]

Re: Question about transmitters and receivers.

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

[terry]

Re: Question about transmitters and receivers.

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

[maddox10]

Re: Question about transmitters and receivers.

Not many channels are more than not enough.

[typhoon_driver]

Re: Question about transmitters and receivers.

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]

Re: Question about transmitters and receivers.

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]

Re: Question about transmitters and receivers.

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.

[psychostorm]

Re: Question about transmitters and receivers.

Is there any known record for largest amount of robots in any weight category in a single arena?

I can't think of any incident where more than 16 were involved.

[daveimi]

Re: Question about transmitters and receivers.

So which setup is cheapest at the minute

[maddox10]

Re: Question about transmitters and receivers.

2.4 GHz. You can have one for less than £50, delivered at the door.

[psychostorm]

Re: Question about transmitters and receivers.

Lowest I've found is £30.

http://www.hurricanemodels.co.uk/engine ... +TX+2.4ghz

http://www.ebay.co.uk/itm/OrangeRx-R610 ... 2a233991be

Alright, it's ugly & not versatile but it is safe & cheap.

[grant_ploughbot]

Re: Question about transmitters and receivers.

There's actually about 80 channel's on the 2.4ghz band. Spektrum recommend the upto 40 TX's on and in use is acceptable - and after that it might work/it might not.
I still don't like the use of all these cheap 2.4ghz radio's for a few reason's - paying £15 for a radio that's controlling a pretty dangerous robot just doesn't sit right with me. I would recommend genuine Spektrum all the time!

One major difference between the cheap brands and Spektrum is that no one knows how any of them other than the genuine spektrum radio's search for clear frequencies before it chooses a new one. This means that when you are getting more and more radio's switched on, we have no idea if the cheap radio's are able to see them all and pick a free channel. Spektrum have spent a huge amount of time in this area and have 2 systems for jumping frequency on their newer systems whilst in use to any of the 80 free channels.