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Radio Transmitter Options for Submersibles

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  • Radio Transmitter Options for Submersibles

    2.4ghz wavelengths have difficulty penetrating water, which is why 72mhz is used, and 75mhz is even better. Please post your radio gear, experiences, what you've found to work, and what you've found doesn't work. Hopefully we can pool our experiences and save each other time, money, and headaches!
    Camp My Instagram @Alpha.Makes

  • #2
    What I have been able to find out is that surface use 75Mhz radios are difficult to find in the US that have enough channels to operate the typical static dive sub. The old surface use radios prior to 2.4Ghz were mostly just 3 channels. Yes, the lower frequencies are needed to penetrate the water. 27Mhz, 72Mhz, 75Mhz etc. as opposed to 2.4Ghz. It is unfortunate but the lower frequencies are not a big market in the US for radio manufacturers as most RC cars or boats have transitioned to 2.4Ghz as well which is fine for them. In addition, it is sometimes desirable to have proportional control along with analog switches for some of the dive systems out there. Radios that would fit the bill are more likely to be 72Mhz which are still acceptable for aircraft use but risk interfering with someones plane or being interfered with if on the same channel. I have also heard that most regattas require 75Mhz channel sharing via clothes pins so if you desire participating in such you need 75Mhz equipment. In Europe 40Mhz equipment is readily available but is not legal in the US for RC. All is not lost however as it is possible to "re-tune" some 72Mhz radios to 75Mhz operation. One such radio is the Futaba T9-CAP. I recently snagged one off of eBay in excellent condition for a little over $100.

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    It has enough channels and the right type, is programmable, will hold enough models to satisfy me and it can be "re-tuned" to 75Mhz for about $50 by sending the Tx module and Rx to a place called Radio South. This is what I am going to do. There may be other radios out there that could be "re-tuned" but it has to do with the availability of the necessary crystals. I originally inquired about a JR radio I found for free but was informed that the crystals are not available for them. At least that is what I was told. The problem is that while not impossible, radios like this are becoming harder to find because they are considered "old tech" which makes it harder for the true sub captains out there who want a sub that dives.

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    • #3
      Bob Martin of the Nautilus Drydocks has a stock of VEX 75Mhz radios which are 6 channel and work fine for most sub applications in the US using normally aspirated water tight cylinders. If I am not mistaken they were at one time used for robotics. They don't have the proportional control functionality needed for some applications but can be set up with the servo stepper he also provides to allow additional control capability beyond what the radio itself can do. That is another option at least.

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      • #4
        Something that I am running into is that the BLM or Battery Link Monitor and AD2 pitch controller I got from the Nautilus Dry Docks don't seem to play well with the PCM receiver I am trying to use in my Redoutable. I have ordered compatible PPM receivers to try and all indications are that they will work fine. I will have to send them off to Radio South for re-tuning to get the best range but the crystals in my PCM receivers should work in them as well. All part of the learning process. In time, unless a solution is found we may be confined to just surface runners but I hope a solution can be found.

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        • #5
          Alpha, RCjetdude , How many channels are typically needed for these submarines? Best, LB
          Captain: Got any ideas?
          F/O: Actually not.
          — Captain Chesley B 'Sully' Sullenberger III and F/O Jeff Skiles—

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          • #6
            Originally posted by Elbee View Post
            Alpha, RCjetdude , How many channels are typically needed for these submarines? Best, LB
            Good question. I depends on the sub. The very basic controls of a surface runner would be rudder and throttle just like a boat but to control something that dynamically submerges you would need at a minimum rudder, throttle and dive plane. To make something that is able to statically dive it would take rudder, throttle, most likely a dive plane and a ballast control. It goes up from there as you add features. My Redoutable has rudder, throttle, stern dive plane, ballast control and the forward dive plane (or in my case fairwater plane) is on a separate channel than the stern dive plane. The reason for this is that the stern plane is on a slider and ties in through a pitch controller called and AD2 which acts like a gyro to try and keep the sub level. The fairwater planes are on the control stick like the elevator on a plane and are used to dynamically control depth once the ballast tank is flooded. Obviously the sub has to be moving to accomplish this. On my Redoutable the ballast servo also controls a backup ballast system or emergency blow what is compressed gas which is Badger airbrush propel. The Battery Link Monitor or BLM senses either a low voltage condition from the 3S LiPo or a signal loss from the Transmitter and acts like a failsafe to blow the emergency ballast and hopefully surface the sub or return it to within radio range. It is pretty slick actually. Of course if one wanted to add additional functions they would need extra channels for them. Some very sophisticated subs use ballast tanks that can be very precisely controlled with a combination of analog and proportional channels in addition to the basics. It is fascinating to me.

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