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2.4GHz for the RC Submariner….the next step.

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  • 2.4GHz for the RC Submariner….the next step.

    This post is NOT to merit the pros and con’s of 75Mhz vs 2.4Ghz. That choice is up to you as the operator of the RC Sub YOU own. Honestly, I could not care less on what frequency you choose, or stand behind, or what your definition of what an RC Submarine is. I don’t run your boat, and you don’t run mine.

    BUT, if you think 2.4Ghz is NOT a viable solution for an RC submarine, well you cut yourself OFF from a world of fun and advantages, but at least you can say you dive below PD.

    If you have decided to try it, this is for you.

    As we ALL know, it won’t penetrate the water, period. There is NO denying that, period. So as we ALL know, you need to extend the antenna above the surface of the water. So if you wish to have the boat look like it should, you need a scope or mast of some kind. Which will work for some 90% of the boats out there. Boats that need to stick with the lower frequencies are most likely Sci Fi (Disney NAUTILUS, Fantastic Voyage PROTEUS), Research (ALVIN, TRIESTE) and Special purpose Military (SEAL Delivery Vehicle-SDV). But if you have scopes, and can live with 1-” [31.8mm] minimum scope, this world opens to you with its many advantages.

    For the record, I am NOT the one who came up with the solution, that honor belongs to David Merriman III. He saw a future where “drones” take over the market with their need for High Speed, reliable coms, and everything ELSE above the surface of the water has jumped on this inexpensive tech. This tech allows Manufacturers to build millions of Transmitters and Receivers, leaving the last 10-20k of us in the dust with regards to the market. We can cry and beg all we want, but $$$ talk and BS walks to manufacturers. So again he saw the change, and the need to begin to adapt.

    I only ran with it, because I’d rather get used to it now, before someone tells me to.

    To start, I will refer to his article, I suggest you read it in its entirety.

    How To Adapt The 'New' 2.4gHz Gear To R/C Submarines (Credit: David Merriman III and the Nautilus Drydocks Forums)

    I will show how to make it easy. (Credit: “Sub” Ed)

    Let’s go.

    1: You NEED to understand what type of connection you have on your Receiver (RX).

    You need to pop open the RX and see if you have an IPX connector or if the antenna is directly soldered as in Dave's example.Hopefully you have the IPX connector. It becomes less intimidating, and easier to replace.

    Now let's see the best way to modify it, even if you have to solder as in Dave’s article.

    2: Now you purchase “X” length of RG178 Coax cable with duplicate SMB JACK connectors on each end. These connectors (or similar) are not absolutely necessary, but make life easier as you will see Why two IDENTICAL connectors on each end? Because you can cut that in half, giving you two, X/2 length coax cables to strip and modify the cut coax end (the above above water end) like Dave's example (1.25" exposed center conductor, SEAL with moisture proof heat shrink!!)

    For example: Say you buy 4 feet (122cm) of RG178, cutting in half will give you TWO 2 foot (61cm) length antennas after you seal the “cut” ends! At sea 2 is 1 and 1 is none! Have a spare!! Just try not to exceed 4 ft on the final cut length itself, losses over length do occur, that's why I wouldn't go with a "floating" antenna.

    3-Now on the RX, the dry side. If you have the IPX connector, just purchase a 4” (100mm) length of RG178 with an SMB PLUG connector on one end, and an IPX /u.fl connector on the other, this will mount to your RX.

    If you don’t have the IPX connector, no sweat. Just purchase that length with ONLY the SMB connector. Or like the wet end, purchase an 8” (200mm) length with one on each end, and cut that in half to have two.

    So you ask, “where do I get this stuff?”. Fortunately you have “Sub” Ed.
    I purchased these custom fabricated Cable Assemblies from SuperBat.

    They are NOT expensive!

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    4-Installing the RX Side connector:

    4a-NO IPX, solder connection. If you do have this setup, I again refer you to Dave’s article mentioned earlier for the solder work.

    4b-You have the IPX Connector. No soldering required, I refer you to this video I made:
    2.4Ghz Antenna Swap for RC Submarine Operation

    Just replace one of the two antennas on the RX.

    So friggin' easy, soooo reliable! I love 2.4Ghz!!

    5-Now to the wet side
    Back in Dave’s article, he clearly showed you how to expose the 1.25” [31.75mm] center conductor from the coax shield and seal it. No need to go over it. Then you run it as you choose through the watertight bulkhead. He showed it going through a bulkhead in the ubiquitous cylinder many love to use, and I show here how I set up my RX in my Command and Control Watertight S3 box. You can see why now it’s a good idea to split the RG178 COAX with the SMB Connectors, easier to work with, and easier to replace.

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    Note, because the top of his box is at the surface waterline, I make use of the 2nd antenna I didn't change by running it through a Pressurization/Equalizing Tube, which is capped by that aluminum fuel plug. It is actually above the water in the superstructure when she's surfaced, and I have both antennas available for the best possible reception. It's there, why not use it? The silicone hose of course is used to check for leaks.

    Here I’m running the coax through the superstructure, up the sail and out the NAVSAT mast. The second antenna I did not remove resides in that blue silicon tube, it’s above the water while the boat is in surface trim.

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    Again, don't use a floating wire like some have thought about, just use a very tall mast. As mentioned earlier, the longer the RG178, the more signal loss is incurred. Follow the RC Submariner (and real Submariner creed) Keep it Simple Stupid. Who gives a hoot regarding mast length. No one will go over to the boat and measure it, only you know the ugly truth. If you find people taking a ruler to your masts and antennas, you need new shipmates to hang with.

    Look closely at the middle scope here.
    The first is the Attack Scope (a modified Afghan Sewing needle! WGAS?!?!)

    The second is the NAVSAT MAST, the white portion at the very top encloses the exposed 1.25" 2.4 Ghz antenna. I thread it up from below through the hollow mast and it's held in place with a clip.

    The third is my snorkel induction mast, which is used like a real sub to draw air in through a waterproof diaphragm pump as a LPB to surface, saving on gas for just the Emergency Blow backup.

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    Another point to consider is failsafe. Most modern 2.4Ghz RX’s have control during Loss Of Signal (LOS), meaning you program them to either remain at their LAST seen input, or go to a predetermined servo position set by you. This occurs instantaneously. This is by design for vehicles (planes, drones, fast cars, boats) other than what we want. Specifically, if you have a component that is looking for LOS, such as a gas failsafe, IT WILL NOT SEE IT! The RX will continue to either send the last servo position, or the pre-programmed servo position UP the servo signal wire to the failsafe component.

    This is good in one aspect, you can set it to order “Full Rise” on your dive planes giving the boat a chance to coast back up to Periscope Depth and regain signal if you momentarily lose control at PD.

    There are TWO bad aspects.

    First is your ESC will NOT “Ring up” ALL-STOP unless you program that channel to do so. Unless you do so there’s a good chance your boat will continue on its merry way. Now of course with the aforementioned full rise on the planes she should come back up. But what if it’s a ballast or flooding situation where she’s heading for the deep? Harkens back to the day’s before ESC’s had this built in. So insure you check your TX make and program that Throttle Channel to command an ALL-STOP during an LOS

    Second, GAS or other surfacing failsafe. For those that use the 7 second or so failsafe that counts down after LOS? (IE the SubTech Subsafe or similar) That’s not seeing it either. You CAN program the TX to initiate a blow on LOS, but it will be instantaneous. Your losing the advantage of that 7 second countdown to the blow which would allow the boat to coast back up should have not been paying attention and drifted down. Unless you're super trimmed, no warm spots or differences of water density in a VERY calm lake, you’ll need to be on your toes. Face it, we trim these to within the weight of a BB, especially the 1:96 or smaller which have VERY little tolerance.

    On larger boats such as my 1:48 USS SHARK, ballast trimming is a tad more tolerant, plus I have a mast tolerance on the NAVSAT mast from top of sail to the antenna of 6” [152mm]. But my 1:96 scale Boomer, the USS ULYSSES S. GRANT, has not only a much tighter tolerance with regards to weight trim, but her NAVSAT mast tolerance is on 1-” [38mm]. She keeps me on my toes! That is a good thing, it keeps it challenging! If you don’t want a challenge, this is not your hobby. Go buy that Nikko Sub Toy and run it in your tub.

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    So to get around that problem, I used a Hansen Hobbies NERS v2 Electronic switch. That is programmed to go high and turn “ON” when an LOS condition occurs. This powers a relay, which cuts the “white wire” signal (NC contact on the relay) which simulates an LOS to the standard failsafe detector, which does a countdown and does it’s thing.

    A bit “klugey” as we say in the Engineering field, but it worked!! FWIW, I am currently teaching myself to program Arduino boards (Beetle) to create my own timed Failsafe by monitoring the blow channel servos PWM signal, and begin a countdown when it sees that signal change to a preset servo signal at LOS to activate a “blow”. I’ll share the program once I figure it out. After the code is shared, programming and installing the Beetle is not beyond the skill level of the RC Submariner. And they're cheap too. A failsafe costing $15. Kinda hoping we have a seasoned Arduino programmer out there who might help with the code.

    That’s it for now.

    I’ll leave you with this….

    Again it’s NOT about which frequency is THE best, that’s up to you, the Master and Commander of your RC Submarine. NO one else. I will tell you from experience at one point I was soooo fed up with the glitchiness of 75Mhz, I had planned to run my antennas up the scope like Mike Dory did back in the day to run in that brackish water he was forced to run in. SO I took to this easily.

    I’ve heard it said that if you can’t take it ALL below the surface, it’s not truly an RC Submarine. Well, everyone is entitled to their opinion. But it’s my opinion that very thinking, born of ignorance, does the owner and his shipmates little good. To say that to a newcomer to the hobby, one who could barely afford a boat, much less time and money to scrounge for a dwindling 75Mhz market, or to now have to go get a Ham license, does this Fellowship, much less the hobby, any good. In your “need” to be “correct”, you may be pushing people away. You want the younger generation in? They’ll come with 2.4Ghz providing they’re respected for it

    Your boat, YOUR fun.

    I hope to make a video soon on further details of 2.4Ghz Radio setup for the RC Submarine.
    Last edited by He Who Shall Not Be Named; 06-22-2020, 01:39 PM.
    v/r "Sub" Ed

    Silent Service "Cold War" Veteran (The good years!)
    NEVER underestimate the power of a Sailor who served aboard a submarine.