Hi, I have a set of the 433MHz RCTimer telemetry radios and have noticed the noise level on the ground radio is about 20 units higher than the air module (due to onboard FTDI chip) which is limiting potential range.

I had a look at the datasheet for the HM-TRP module and was wondering.. would it work if I de-soldered the HM-TRP from the RCTimer board and connected it directly to a 3.3v FTDI adaptor via a longer lead (and set the Config pin high and the Enable pin low)?

Thanks

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              • I am trying to modify the ground modules to become air modules because I just have a bunch of ground modules lying around. Their corresponding air modules were damaged from use. I have a bunch other original 3dr modules as well as Rdf900 telemetry sets. I just don't want these ground mods to go to waste since I am already using the RDF900 as a ground station for all the other 915mhz air modules I have. 

      • I'll check it out. Thanks :D

  • Has anyone found a simple way to convert a USB ground module into an air module? I don't want to build one from scratch, I simply want to bypass the USB circuitry. What if I use the wiring diagram posted earlier here to bypass the USB, and for VCC use the APMs 3v3 supply? Or I could find the 3v3 voltage regulator on the ground module and solder in after that?
    Any advice from someone more experienced with electronics?
  • Just been pointed here too so would like to know too please if it worked ok!

    I think I ordered a 5v FTDI adapter though so will have to order a 3.3v
  • Hi, did you work this out?

  • This is really an out of left field question, but is it possible to use a 15 pin D Shell serial plug instead of the USB connector? Would this help with the noise issue? Most note books have them, but they seem to be disappearing off newer models.

    Regards 

  • Hi, i am too getting lots of interference from the usb. I also have one of those 3.3v ftdi adaptor.

    I was wondering if it is possible to connect the 433mhz telemetry to the 3.3 ftdi adaptor but without de-soldering the HM-TRP board and just bypassing the usb from the 433mhz telemetry radio and using wires to go from the HM-TRP board holes to the 3.3v ftdi adaptor?

    I would connect it the same as the diagram from Tom Gilmour but without de-soldering it

    Thanks for the help.

  • Thanks guys.  So the setup below would work? 3692820004?profile=original

  • Hi, I did that and it's not difficult.

    I put the ground radio module in a small RF shielding enclosure too. What exactly is the correct way to kill noise travelling along the cable before entering the shield, I am not quite sure. The length of the cable was, of course, with the serial signals, not USB.

    I can't tell you how much it improved things because I did not even bother testing it before the conversion. But I generally had a much better downlink than uplink, so it can't have been all that bad.

    However in general the HM-TRPs performed lousily, I think.. I had much much better results with XBee Pro's with decent antennas on them (one biquad on ground, four of them matched for long range).

    Regards

    Soren

  • It should work.

    You can leave Conf and En floating (unconnected).

    Im doing my own "3DR radios" 433&868 MHz with reprogrammed HM-TRPs on custom PCB (of course without integrated USD-UART interface) and I always leave this pins floating.

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