user15434: I am trying to figure out how to get 2 Arduinos to talk back and forth from one another using cheap simple RF modules. I have a total of 4 RF modules (2 receiver and 2 transmitter) and 2 Arduinos. I need Arduino A to send about 3 variables to Arduino B, and I need Arduino B to send 1 variable back to Arduino A.
When I attempted 2 way communication, I programmed Arduino A to broadcast constantly, while having Arduino B trade off between receiving once, then sending once on every other loop. This resulted in Arduino B also only broadcasting, and was not receiving any signal from Arduino A.
My other attempt was to have Arduino B send for about 250 ms, then receive for 250 ms, and repeat. This worked as long as Arduino A was only broadcasting, but as soon as I had Arduino A doing the same thing, the clock on each seemed to be slightly off and there would be periods where both Arduinos were sending, or where both were trying to receive, so it was also very unreliable. 
Is there a reliable way to do two way communication with this kind of hardware, or would I need transceivers to do this kind of project?

user10394: If the RF Modules you are mentioning are the ones I am thinking of they do seem to be very special bits of kit.  I have tried Bluetooth you can get cheap HM05 modules (Might be the wrong number you want the one that can be the master or slave).  These were a bit better but don't have the range.
My personal fav at the moment would be a ESP8266, no I have never hooked one up to an Arduino, but it can be done fairly easily.  You should get 100m range (in ideal circumstances) and you can get aerials to boost that.  You can also set one up as a repeater between two wifi segments.
Whatever you decide you might want to change your code slightly so that one Arduino sends a time signal and the other doesn't send its data until its turn.  Or give them GPS receivers and pull the time from there.

15434: <p>I am trying to figure out how to get 2 Arduinos to talk back and forth from one another using cheap simple RF modules. I have a total of 4 RF modules (2 receiver and 2 transmitter) and 2 Arduinos. I need Arduino A to send about 3 variables to Arduino B, and I need Arduino B to send 1 variable back to Arduino A.</p>

<p>When I attempted 2 way communication, I programmed Arduino A to broadcast constantly, while having Arduino B trade off between receiving once, then sending once on every other loop. This resulted in Arduino B also only broadcasting, and was not receiving any signal from Arduino A.</p>

<p>My other attempt was to have Arduino B send for about 250 ms, then receive for 250 ms, and repeat. This worked as long as Arduino A was only broadcasting, but as soon as I had Arduino A doing the same thing, the clock on each seemed to be slightly off and there would be periods where both Arduinos were sending, or where both were trying to receive, so it was also very unreliable. </p>

<p>Is there a reliable way to do two way communication with this kind of hardware, or would I need transceivers to do this kind of project?</p>
 10394: <p>If the RF Modules you are mentioning are the ones I am thinking of they do seem to be very special bits of kit.  I have tried Bluetooth you can get cheap HM05 modules (Might be the wrong number you want the one that can be the master or slave).  These were a bit better but don't have the range.<br>
My personal fav at the moment would be a ESP8266, no I have never hooked one up to an Arduino, but it can be done fairly easily.  You should get 100m range (in ideal circumstances) and you can get aerials to boost that.  You can also set one up as a repeater between two wifi segments.</p>

<p>Whatever you decide you might want to change your code slightly so that one Arduino sends a time signal and the other doesn't send its data until its turn.  Or give them GPS receivers and pull the time from there.</p>
