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How To Adapt The 'New' 2.4gHz Gear To R/C Submarines

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  • #31
    Originally posted by Bob Gato View Post
    It is really dependent on the coax cable that you are using the small cable that typically is used in submarines is more attenuating but this should give you an idea...

    ​​​​A common, relatively inexpensive cable for short runs to a Wi-Fi antenna is LMR100. At 2.4 GHz (the common Wi-Fi band), 15 feet of LMR100 will result in a signal loss of about 6 dB. That is equivalent to dropping power down to just about 25 percent of what it was (each 3 dB equals a 50 percent gain or loss in power).Jun 12, 2016

    It's all on the internet-just ask Google.
    Thanks this is the type of technical information I need, I am not good at electronics at all, not in radio signals, and loss over cable.
    I have bought this coax cable ( 28AWG UL1185, copper wire structure 7/0.12 tinned copper wire, winding 20/0.1 tinned copper wire, outer diameter: 2.3mm). I don't know what all these numbers mean. I just know AWG is the diameter in american standards.
    Can anybody tell me if this is suitable for carrying 2.4GHz signal and for how long without too much signal loss??

    That would be absolutely marvellous! thanks a lot!


    This is the coax cable:
    https://fr.aliexpress.com/item/32894...27426c37EBUoEZ

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    • #32
      Originally posted by RCJetDude View Post
      I am going to give this a try on my current Ohio project. So much excellent information here by David and Ed. Thank you gentlemen.
      Are you going to try 2,4GHz float type antenna too!??

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      • #33
        Originally posted by MakeHobbyRC View Post

        Are you going to try 2,4GHz float type antenna too!??
        No. Just going to put the antenna up the periscope.

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        • #34
          Originally posted by RCJetDude View Post

          No. Just going to put the antenna up the periscope.
          Ah right cool! might be easier. I might not get it to work at all... let's see... That's how I started building the ANTENNA FLOAT :





          and


          Last edited by MakeHobbyRC; 08-26-2020, 07:44 AM.

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          • #35
            Well that's not going to work...my friend... it's model submarines and you are in over your head..I strongly suggest that you reread the many threads on extending 2.4 antennas.

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            • #36
              Hello David and all,

              I have been reading all the comments and posts regarding adding an extension to a 2.4 ghz antenna. The questions that I am going to be asking have already been covered, I am asking them for the sake of clarity and to make sure that I am on the right track. I have a receiver , a Turnigy iA6C. It has twin antennas.

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              It does not have IPX connectors. I took it apart and found this.

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              I presume that the first blob of solder is the shield pad and the second is the antenna pad. Does that look right? I have done a drawing to clarify my thinking.


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              So in a nutshell at the receiver end it is about grounding the outer sheath / shield and connecting the inner core cable to the antenna connection and then exposing the other end however far at precisely the right length of exposed core?

              Thanks for the clarification

              Davidh

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              • #37
                You got it right. And that antenna exposure at the up-in-the-air end of coax core (antenna) should be exactly 1.25" in length. Which makes it a full-wave 2.4gHz antenna.

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                David
                Resident Luddite

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                • #38
                  I read somewhere that if you are using a 2.4 ghz system with a brushed motor drive you don't need to install noise suppression capacitors. Is this true?
                  Make it simple, make strong, make it work!

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                  • #39
                    Originally posted by redboat219 View Post
                    I read somewhere that if you are using a 2.4 ghz system with a brushed motor drive you don't need to install noise suppression capacitors. Is this true?
                    Don't know. But, why take the chance of finding out in the middle of the lake while in submerged trim. Two ounces of prevention... and all that happy horse-****.

                    A truly Dumb question!

                    Why not get underway with a leaking WTC? Why bother with post-mission checks? Why not yank out that transmitter antenna in the middle of a lightning storm? Why not make moves on Harley Quinn in front of Mr. J?

                    Dumb...DUMB.. DUMB!

                    David
                    Resident Luddite

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                    • #40
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                      Make it simple, make strong, make it work!

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                      • #41
                        Thanks David for making simple sense of this. My radios are slowly dieing and it's time I went 2.4 ghz.

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                        • #42
                          I have found that personally I like the simplicity of 2.4 GHz and radio programming capability. PD is fine for me.

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                          • #43
                            Hello all,

                            I spent yesterday afternoon, desoldering a 2.4 ghz receiver , and slowly followed the above instructions to attach a new longer lead and make the small antenna at the end of the coax. Put it inside a cylinder with a servo and small battery and antenna coming out endcap sealed, and then tested it. IT WORKS PERFECTLY.

                            But, I then pushed the antenna down underwater to a depth of about 50 mm and it kept working. Below that and there was no reception. I raised the antenna once again to within the 50 mm range and my tx beeped and the servo started moving again.

                            Then this morning I used a standard 2.4 ghz rx of the same model ( with no modification ) and did the same thing, just to check that it would not work at all with the cylinder slightly below water level. Well it worked fine to a depth of 50mm.

                            I am very surprised, but delighted at the same time. I intend to run my upcoming U -23 with 2.4 Ghz

                            I thought 2.4ghz does not work with an antenna underwater? Have I missed something?

                            David H

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                            • #44
                              Originally posted by Davidh View Post
                              Hello all,

                              I spent yesterday afternoon, desoldering a 2.4 ghz receiver , and slowly followed the above instructions to attach a new longer lead and make the small antenna at the end of the coax. Put it inside a cylinder with a servo and small battery and antenna coming out endcap sealed, and then tested it. IT WORKS PERFECTLY.

                              But, I then pushed the antenna down underwater to a depth of about 50 mm and it kept working. Below that and there was no reception. I raised the antenna once again to within the 50 mm range and my tx beeped and the servo started moving again.

                              Then this morning I used a standard 2.4 ghz rx of the same model ( with no modification ) and did the same thing, just to check that it would not work at all with the cylinder slightly below water level. Well it worked fine to a depth of 50mm.

                              I am very surprised, but delighted at the same time. I intend to run my upcoming U -23 with 2.4 Ghz

                              I thought 2.4ghz does not work with an antenna underwater? Have I missed something?

                              David H
                              The inverse square law is your friend. How close was the transmitter antenna to the receiver antenna during this 'test'? Did you try it with at leas a 50' cross-range between the two?

                              David
                              Resident Luddite

                              Comment


                              • #45
                                The air/water interface is the biggest challenge. High frequency "skips" off the surface. Get more than a few dozen feet away and I'll bet you don't get more than an inch of water penetration (if that).

                                I set up my high frequency boats to automatically command 1/3 throttle and full rise on planes with loss of signal. In most runs if I accidentally dip the antenna, I don't even notice as the boat simply rises until the antenna pops out again.

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