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

[mackrackit]

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

I think that might be the answer to your question. The faster one is using more power so less is available to the transmitter.

It does not take much of a voltage drop to make a big difference.
It is all about wattage.

[sirvo]

I think that might be the answer to your question. The faster one is using more power so less is available to the transmitter.

As I editted:

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

The delta current between crystals is about 0,1mA. It's too small to cause an effect using this powerfull battery, don't you agree?

Thanks!

[Ioannis]

Have you tried to exchange the modules (only modules, not the antennas or the PIC driving part) and see if there is any difference?

Ioannis

[sirvo]

No, I haven't yet..

I'll do the exchanging and let you know the answer.

Thanks again.

[rsocor01]

Sirvo,

Are you sure all the modules are transmitting at the same frequency? The higher the frequency the higher the transmitted power, but also the higher the frequency the higher the attenuacion. Longer wavelenth signals travel farther than shorter wavelength ones.

Robert