RF communication (433MHz)

[sirvo]

Hello...

We have 4 boards with exactly the same components (except the xtal) (PIC16LF648A, RXQ2 RF module) and it`s been communicating really fine.

We went out on a distance test to make sure that RXQ2 module could achieve the range of 200m, as specified on the data sheet. Well, it DID work for the four boards.

However, boards A and B, uses a 2MHz crystal oscillator (pic external osc).
Boards C and D uses a 4MHz crystal.

Why? Because we need to save power, as it is battery powered. Slower speed means less power consuming.

So, the question is: WHY the boards A and B achieved a range up to 320m and boards C and D achieved a range up to 240m?

The antenna is all the same length, the boards are identical, the serial comm. between RXQ2 and PIC are all 9600, 8, N 1, the firmware is equal and so on...

If anybody could give me a reasonable answer to it, I will be really glad.

(forgot to tell you: The batteries were brand new, 16500mAh, with top current of 400mA. The TX current of RXQ2 gets at most a peak of 16mA)

Thanks in advance.

Sylvio