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Why are Sub Radios so Hard to Find? - 10/1/2011 1:45 AM   
Buddy3000


 

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From: , VA, USA
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I recently purchased a Neptune SB-1 and the Trasmitter and/or Receiver has issues. I did the typical distance test with a battery pack connected and all other devices powered down and disconnected from the receiver except the servos. In about 30ft the servos begin to flutter. If I connect the ESC or the control module the fluttering gets much worse. In the water the distance is about 3ft befor the failsafe kicks in.

I figure I have to replace the radio system. With everything I've read, all the recomendations seem to say to stick with type of system that came with the sub. However the 75mhz  FM systems see to be few and far between.

Can anyone recommend a system that's readily available, reliable and not rediculously expensive?



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RE: Why are Sub Radios so Hard to Find? - 10/1/2011 2:48 AM   
yf222000


 

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Status: offline 		I have not try the Neptune yet, but radio signals works similarly in a lot of subs. Before you try to change out the entire radio
setup, try to reroute the antenna within the watertight compartment. Try to put it as far a way away from the motor, or the speed controller
as you can. I run my converted Revell Gato model, and its compartment is even smaller than your Neptune. I used to have the same issue at first, but
after trial and error, rerouting the antenna seems to have worked.

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RE: Why are Sub Radios so Hard to Find? - 10/1/2011 5:03 AM   
Buddy3000


 

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Status: offline 		Thanks for the reply, I have tried to reroute the antenna a few times, some tries had better results than others, but none seemed to solve the problem. I'm really discouraged in that, this was a factory built unit and I've heard of such successful dives right out the box.

I did an experiment and removed the reciver and one of the servos, put them in a jar at the bottom of my pool. I rigged it so that an LED would illuminate when the servo was activated. That test seemed somewhat successful in that I was able to control the servo under 3ft of water from about 30ft. The only problem was that it was done at night so I could see the LED from a distance. I don't know that it illiminated the flutter, which causes the failsafe to kick in. Also my test allowed me to better spread out the antenna which problably also improved perfomance,

I have a feeling that the radio may need retuning, but I have no idea where to get that done or if it's even worth it.

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RE: Why are Sub Radios so Hard to Find? - 10/1/2011 2:28 PM   
subsinker



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Status: offline 		Hi,

I agree with the previous poster. Before changing out to a different radio system you may want to do a bit of detective work. I have found that when servo wires are too close to each other (typically they are because a sub us cramped for space) then you will want to put RF chokes on the wires. You can pick them up at just about any electronics store. If you look at computer cables you will see them everywhere. It will go a long way to preventing radio flutter or interference. Make sure when you route the antenna it does not touch anything metal or carbon fiber. That can cause the glitching you are talking of. Make sure your batteries are fully charged. That can cause the glitches. I personally do not own a TT Neptune sub but have heard good things about the radio system. No, it's not a top of the line do-all radio but what the heck, the whole sub costs $500.00 That's a bargain if you ask me.

Another option is to purchase a Futaba 72Mhz radio used and have Futaba in Champaign Illinois convert it to 75Mhz. They used to do that at a fairly cheap price. Contact them for more info. I personally have two Futaba sub radios, a Robbe F-14 (75mhz) and a Futaba 7C (75mhz) The 7C is essentially an airplane radio that they converted to surface frequency. Works great and I have had it for years.

Hope that helps!
Pete

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I''''m sorry Spanky, I have to live my own life- Alfalfa

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RE: Why are Sub Radios so Hard to Find? - 10/1/2011 4:34 PM   
Buddy3000


 

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Status: offline 		Cool thanks for the info. I've tried eveything you mentioned with the exception of the filter chokes. I am still going to look into replacing the radio, at least it'll put my mind at ease that that is not the problem.

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RE: Why are Sub Radios so Hard to Find? - 10/1/2011 8:01 PM   
yf222000


 

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Status: offline 		So, if you were able to rigged the LED to turn on when the servo responses to your command from the transmitter, which means that
the radio system is functioning properly. I would have to assume that if there was glitches with the servo while it was under water,
you would have seen the LED fluctuating as well. If none was detected, then the radio setup is fine. You might want to try to locate the
source of interference elsewhere within the watertight hull. My guess would be a loose connection, or some kind of strained in the motor
when you commanded it to run or dive. The strain in one of these motors could send electrical noise right to the receiver's antenna and
caused it to have glitches. What I did see with my own sub was that, if the battery was low on charge, glitches happened when I throttled it
forward or backward. Charged the battery full, and the problem went away. Try that to see if it may be the cause. Good luck.

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RE: Why are Sub Radios so Hard to Find? - 10/2/2011 9:54 PM   
Buddy3000


 

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Status: offline 		Here's the latest.

I decided to do some more experimenting to determine the problem. With just the receiver, two servos and a battery pack, I still noticed the fluttering, some times it would be worse than others. I happened to drop the receiver on the table and the flutter stopped. I thought I broke something, but everything was working fine. I continued with my experiment. I put  the Rx stuff in the jar and turned it on. Again the fluttering. I decided to tap the Rx to see if it would have the result as dropping on the table. Low and behold it did! Hmmm. I installed the Rx back in the sub made sure everything was still flutter free, put the sub in the pool. Best perfomance I've seen since I got the damn thing. I was able to dive to about 3ft at a distance of about 8ft. That's hardly what this thing is supposed to be capable of, but I actually got to have a little fun with it.

Now the questions. I'm thinking that there is either a problem with the Rx or the Rx Crystal. I'm not at familiar with Tx/Rx compatibility so I don't know what my options are.

1. Can I use crystals from another radio brand?
2. Will another brand of Rx be compatible with my current Tx?

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RE: Why are Sub Radios so Hard to Find? - 10/4/2011 2:48 AM   
caswell


 

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Status: offline 		Get a WFLY radio with a Sombra Labs receiver. That should solve your problems.

PM me for details






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RE: Why are Sub Radios so Hard to Find? - 10/4/2011 4:03 AM   
Hydro Junkie


 

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Status: online 		I would also consider a 27MHz radio system over the 75 MHz. It's well known that the higher the frequency, the more suseptible it is to being reflected by the water surface. This is why there was so much trouble using the spectrum radios with boats, reflected signals. This is also the reason actual submarines use a VLF radio for intersub comunications.

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RE: Why are Sub Radios so Hard to Find? - 10/4/2011 3:59 PM   
GibsonMichael


 

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From: Pekanbaru, INDONESIA
Status: offline 		Excuseme. Sorry For Make a sillly question coz i never make an RC Submarine before but i want to ask is futaba Robbe F-14 (75mhz) and a Futaba 7C (75mhz) can work properly in water? d>_<b


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RE: Why are Sub Radios so Hard to Find? - 10/4/2011 10:30 PM   
Buddy3000


 

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quote:

ORIGINAL: Hydro Junkie

I would also consider a 27MHz radio system over the 75 MHz. It's well known that the higher the frequency, the more suseptible it is to being reflected by the water surface. This is why there was so much trouble using the spectrum radios with boats, reflected signals. This is also the reason actual submarines use a VLF radio for intersub comunications.



Hmmm, I'm a little surprised at your recomendation. In all of the threads and research I've done the sub builders seem to recommend the 75mhz FM radio. This is the first recommendation for a 27mhz that I've seen.

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RE: Why are Sub Radios so Hard to Find? - 10/4/2011 11:00 PM   
Hydro Junkie


 

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Status: online 		While there is nothing wrong with the 75MHz band, it doesn't carry as far as the lower frequencies due to being more line of site restricted. I learned this while in the Navy way back when while I was in Avionics school and a communication/navigation/radar tech on the now being phased out EA-6B Prowlers. The higher the frequency, the more line of site it is. To take it one step further, the long range radio system used was in a lower frequency band than the standard VHF band used not just by the military but also commercial jetliners. Getting back to the 27MHz systems, due to the longer wavelength, there is much less signal reflected by the water's surface so the underwater range is greater. I would recommend being a little more cautious in using this band as it's also usable for aircraft as well

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RE: Why are Sub Radios so Hard to Find? - 10/5/2011 8:48 PM   
roedj


 

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Status: offline 		For the purposes of R/C submarines there's no appreciable difference between 27MHz and 75MHz. The main difference is that 75MHz radios are FM while most 27MHz radios are AM. You definitely want FM.
I have absolutely no ties to Caswell (see his reply above) but he does carry radios that will serve your purposes.

Here is the link:

http://www.caswellplating.com/models/transmitter.html

Take a look. Any more ?'s - just ask.

Dan

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RE: Why are Sub Radios so Hard to Find? - 1/6/2012 12:22 AM   
2daice


 

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From: merrimack, NH, USA
Status: offline 		look up this company on line Alexanderengle. They sell a 40 mhz radio. They DO subs only. I have their u177 and the only limit is sight. I sail in a lake use a 1/16 x 3ft  threaded rod with a red straw on top to keep track of it. I use it 100 ft away under water no problems.

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