External Hitec HF module

[Javier Garcia]

I want to transmitt the radio signal by an external Hitec HF module. If you see the module pins face, from left to right:
I connected the pin 1 to PPM in; pin 2 to 12 V; pin 3 (not used); pin 4 to ground; and pin 5 to antenna, but it doesn´t work.
What am I forgetting?

[AnthonyRC]

If you are taking the PPM signal out of the buddy-box connector remember that you need to invert it (in most cases) before feeding it into the module.
A simple transistor switch will do it.

[Javier Garcia]

Thanks for your answer.
I thought about that, but the Eclipse is able to send in positive and negative pulses, and it is controled by the main PCB (I think), so, to the HF module, will go positive or negative pulse, and would work either way.

Or it isn´t?

[AnthonyRC]

Thanks for your answer.
I thought about that, but the Eclipse is able to send in positive and negative pulses, and it is controled by the main PCB (I think), so, to the HF module, will go positive or negative pulse, and would work either way.

Or it isn´t?
I don't know much about the Eclipse, but certainly when I take an HF module from a Futaba 9C, and mount it externally, I need to invert the PPM input .

[Javier Garcia]

Thanks, Anthony!
Yes, you are right, the PPM pulse was negative.
I inverted the PPM pulse, but didn´t work

After that I looked for a difference in PPM signal voltage: at the module pin I found 0,5 v; but at the DSC, when inverted, 5,3 v. With a 4,7 Zener diode, it went down to 0,6 v.

But it doesn´t work. I checked at the external module pins, and voltage is 9,8 v, the pulse is positive as the TX (the pulse trains are there), and 0,6 v voltage from the PPM signal.

Any idea?

[Eric_N57105]

I can't add anything to the solution, but I was wondering in what application would you want to have the RF module external?

Eric

[Javier Garcia]

For security reasons.
If you install two receivers in the model, working in differents frecuencies, you get more security if there is an interference in one of them.

It´s very ussual to install two receivers in big planes, even mandatory in France. Even, you could use a diversity receiving system.