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reception gone after 1 foot of depth???

R/C Submarine modelers

reception gone after 1 foot of depth???

Postby maverick pro » Tue Jul 28, 2009 11:34 pm

hey guys...im lost here, ive routed my antenna out side the wtc and out side the sub and still cant get past a foot of water with out complete loss of control. it happens with motor running and without.

the setup...
7.4 volt 2 cell lipo
futaba skymaster radio
futaba fm 75 mhz 8 channel
2 micro servos
apc
viper esc
graupner 280 motor with 3 capaciters
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Postby Skip Asay » Tue Jul 28, 2009 11:38 pm

A couple of questions:
1. Is this fresh water or swimming pool?
2. Is the end of the antenna waterproofed?

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Postby maverick pro » Wed Jul 29, 2009 12:34 am

hi...its a pool with no chemicals at the moment. starting to turn green :lol:
yes i did make sure the antenna was waterproofed.

thanks...mike
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Postby petn7 » Wed Jul 29, 2009 6:57 am

What frequency are you using again?

I am not aware of any 75 MHz frequency on Channel 8. I believe Channel 8 is on the 50 MHz band. Or perhaps you are saying your receiver has 8 channels?
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Postby Ramius-II » Wed Jul 29, 2009 12:12 pm

Just a few questions. Which make and model of transmitter are you using and which receiver? Is it possible you have a mismatch between the transmitter and receiver such as having the transmitter that is PCM and the receiver is set to PPM? Do you know if the transmitter is putting out full power? When you routed the antenna, did you accidently cross a metal surface? Is the antenna still at full lenght, that is it has not been cut or have any cuts in it? Have you checked that the receiver has the full 4.5 volts and the voltage does not sag (go down) when in use?

Best, Ed
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Postby maverick pro » Wed Jul 29, 2009 1:10 pm

hey guys...not its a 8 channel reciver on 75 mhz and channel 87. the radio and reciver is futaba fm not pcm. the antenna has never been cut and is at its full length. the radio tray is aluminum the reciver sits on and the battery. could that possibly be the problem?

late last night i routed the esc away from the reciver. im going to test run it today and see what happens.

thanks again...mike
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Postby Ramius-II » Wed Jul 29, 2009 1:27 pm

Hi Mike, I was thinking more of how the receiver could be de-sensitized such as running on a low voltage or maybe the receivers front end became blown from over heating or by too strong a signal. The other posibilities are the transmitter is putting out low power, there is a problem with the transmitters antenna. FM is a type of transmitter (Frequency Modulation) and there are two common types of modulation of an FM signal, PCM (Pulse Code Modulation) and PPM (Pulse Position Modulation). There is typically a switch or jumper on the receiver to select the "Mode". Usually when the servos or motors are operating they will draw so much power the receiver ends up not having enough voltage to operate correctly. Simple, small voltmeters cost about $10.00 and are very useful.

Best, Ed
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Postby maverick pro » Wed Jul 29, 2009 5:33 pm

Ramius-II wrote:Hi Mike, I was thinking more of how the receiver could be de-sensitized such as running on a low voltage or maybe the receivers front end became blown from over heating or by too strong a signal. The other posibilities are the transmitter is putting out low power, there is a problem with the transmitters antenna. FM is a type of transmitter (Frequency Modulation) and there are two common types of modulation of an FM signal, PCM (Pulse Code Modulation) and PPM (Pulse Position Modulation). There is typically a switch or jumper on the receiver to select the "Mode". Usually when the servos or motors are operating they will draw so much power the receiver ends up not having enough voltage to operate correctly. Simple, small voltmeters cost about $10.00 and are very useful.

Best, Ed


i always thought that if running ppm there would be no way to control a reciver that was pcm. even if i get in the pool with no motor running and set it at the bottom of the pool i have no control what so ever. i never thought that the micro servos and the little 280 motor would pull the 7.4 volt lipo down that fare. i will like you said get a voltage meter to check and see.

thanks again...mike
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Re: TDS

Postby maverick pro » Wed Jul 29, 2009 5:35 pm

sunworksco wrote:If the pool has not been drained for several years and replenished with fresh water the total dissolved solids could be higher than salt water.Swimming pools normal tds levels are usually below 700 ppm.I have seen some public pools higher than 2500ppm which means the facility should be closed by the health dept.Pool water sanitizers will not oxidize and sanitize the water when the tds goes too high and the conductivity of the suspended solids are too much for radio signals to penetrate.


i will try and find a better water sorce and see what happens. the problem is most water around here is salt or brakish. your right the pool has not been drained then filled fresh in a long time.

thanks again...mike
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Postby JWLaRue » Wed Jul 29, 2009 5:48 pm

Mike,

I don't think this has been asked.....

How far away can you move from the boat when it's not in the water and still have control?

-Jeff
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Postby Ramius-II » Wed Jul 29, 2009 5:48 pm

Normally you are correct the servos and motors when running will not cause a voltage drop. However, the startup current draw can be quit high. Two other thoughts, it could be that either the power or ground connections for the receiver could be poor. You may wish to ground the receivers tray. Antennas actually have two sided and grounding the tray may allow the tray to act as the second side of the antenna.

Best, Ed
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Postby maverick pro » Wed Jul 29, 2009 11:28 pm

JWLaRue wrote:Mike,

I don't think this has been asked.....

How far away can you move from the boat when it's not in the water and still have control?

-Jeff


so fare i havent don a range check. it works on the serface no problem. will try it tommaro and let you know what happens. im thinking at least 50 paces and it should still work antenna down???

thanks again...mike
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Postby maverick pro » Wed Jul 29, 2009 11:30 pm

Ramius-II wrote:Normally you are correct the servos and motors when running will not cause a voltage drop. However, the startup current draw can be quit high. Two other thoughts, it could be that either the power or ground connections for the receiver could be poor. You may wish to ground the receivers tray. Antennas actually have two sided and grounding the tray may allow the tray to act as the second side of the antenna.

Best, Ed


never thought of that...if the problem continues after a reciver change i will give it a try.

thanks again...mike
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Re: TDS

Postby SteveNeill » Thu Jul 30, 2009 12:22 am

sunworksco wrote:If the pool has not been drained for several years and replenished with fresh water the total dissolved solids could be higher than salt water.Swimming pools normal tds levels are usually below 700 ppm.I have seen some public pools higher than 2500ppm which means the facility should be closed by the health dept.Pool water sanitizers will not oxidize and sanitize the water when the tds goes too high and the conductivity of the suspended solids are too much for radio signals to penetrate.


Correct!! This is what happened to my pool after years of not changing the water. Once the water was changed I could dive straight to the bottom at 8 ft with no problems. Try to find a fresh water pond to run it in a save yourself the trouble. If you have good reception at a local lake, then you need to change your pool water.

Steve
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Postby maverick pro » Thu Jul 30, 2009 12:30 am

hey steve...will do. im going to have the same problem with brakish to right?

mike
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