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Old Apr 09, 2013, 06:47 AM
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pkboo's Avatar
Almere The Netherlands
Joined Sep 2006
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Question
2.4Ghz and elongating the antenna

Hey Guys,

I know that 2.4Ghz is not advised to use under water However having the receiver that fits perfectly, having good experience with competition boats with 2.4 and building a surface runner with a small possibility to make it a dynamic diver I thought of elongating the antenna so that it sticks out of the water when diving!

Three questions is it possible to elongate the 2.4Ghz antenna without any loss of signal and will it increase the possibility of me disturbing others or viceversa my signal being disturbed? If there's any other eventuality that could happen please also state.

Appreciate the answers I get

Boo
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Last edited by pkboo; Apr 09, 2013 at 06:49 AM. Reason: Grammar BooBoo
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Old Apr 09, 2013, 11:03 AM
ir3
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United States, CA, Los Angeles
Joined Dec 2007
294 Posts
PKBOO,

The length of an antenna is optimized for the frequency range that it will be subjected to. At 2.4Ghz slight changes in antenna length will greatly reduce the antennas efficiency. Changes in antenna length at the lower frequencies such as 75Mhz, are a lot more tolerable. If 2.4Ghz were doable for submarines, everyone would be doing it. I wish there was a simple solution but my Engel VIIC will be running at 75Mhz.

Hope this helps,

IR3
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Old Apr 09, 2013, 12:34 PM
Is life for real?
pkboo's Avatar
Almere The Netherlands
Joined Sep 2006
1,324 Posts
Ir3, thanks for the heads up... that just means that I have to figure out how to get the receiver higher up... which is not easy on a 1:125 U99 ..... and yes I have a 40Mhz Multiplex waiting for my 1/72 type VII. Boo
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Old Apr 09, 2013, 01:01 PM
Submarines, etc.
tsenecal's Avatar
Arvada, Colorado
Joined May 2005
1,603 Posts
if you have a spektrum receiver that can use remote receivers, this might be a suggestion, it is designed for carbon fiber sailplane fuselages, carbon fiber can block 2.4ghz reception as well as water:

http://www.horizonhobby.com/products...ceiver-SPM9546

run the antenna up the periscope, and then you will be limited to that depth. from personal experience, i know the receiver will fall into failsafe mode when the antenna gets about 1/2" below the surface.

reading the description, it appears you can get antenna extensions up to 36" long.


this really isn't an answer for everyone (me included), but it would kind of let a 2.4ghz submarine work like the guys have been doing 75mhz in saltwater for decades.


you can get a 6 channel receiver capable of using the remote for as little as $69.00:

http://www.horizonhobby.com/products...iver-SPMAR6210
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Old Apr 09, 2013, 01:44 PM
Is life for real?
pkboo's Avatar
Almere The Netherlands
Joined Sep 2006
1,324 Posts
Thanks Tsenecal, will have to check how far she'll be able to dive, I'm not to keen to spending that money right now but I do have a spectrum transmitter and I'm using a clone DSM2 receiver in the sub. I do have AR500 receivers but it they don't carry the connection to a 2nd receiver. Boo
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Old Apr 09, 2013, 07:35 PM
Submarines, etc.
tsenecal's Avatar
Arvada, Colorado
Joined May 2005
1,603 Posts
pkboo,

it looks like hobbyking/orangerx make a 6 channel receiver that is capable of using a satellite receiver for $13, saving you a few dollars off the real spektrum (over $50)

http://hobbyking.com/hobbyking/store..._Failsafe.html

you would still have to use the spektrum satellite, since it has the extended length antenna, seems that orangerx doesn't make one like it.
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Old Apr 10, 2013, 09:13 PM
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United States, AZ, Yuma
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i check the range in a bucket of very bad water ( lots of minerals).
i got over 12 inches of range before i bottomed out with a dx5e and a r415 reciever.
YMMV.
ive been toying with this idea for a while now. tho the rx might lose signal and run all the way to the bottom! a failsafe rx would be needed.
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Old Apr 10, 2013, 09:39 PM
ir3
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United States, CA, Los Angeles
Joined Dec 2007
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An interesting experiment. You should try it in water that is similar to the environment that the boat will be in. Filthy water loaded with various chemicals is actually a pretty good conductor at certain frequencies. The Navy ULF (Ultra Low Frequency) communication system with submerged submarines depends on the fact that the water is very salty and full of conducting minerals.

Experimenting like this is very rewarding regardless of the outcome.

IR3
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Old Apr 10, 2013, 10:36 PM
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Nemo, how wide was the bucket? if it was 12 inches, then the receiver was only 6 inches away from a surface
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Old Apr 11, 2013, 03:25 AM
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year, buut that bassumes the signal was comming at the sides.... righht now i do hav access to a pool tho.
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Old May 11, 2013, 05:49 AM
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Espaa, CL, vila
Joined Sep 2008
569 Posts
Hi guys.

Im not on subs yet but I can tell you some things Ive experienced with 2.4GHz receivers.

I used to race Spektrum Rxs few years ago and then switched to Associated/Thunder Tiger 2.4GHz systems. These receivers feature coaxial antennas with a plug on one end (same plug as WiFi antennas...) and a "peeled" portion on the other end.








This exposed portion of antenna (in fact not totaly exposed, just ground net removed around it) is the one and only section that catches radio waves from Tx, and its lenght is very important to get the desired range.

But Ive found you can make this portion longer (the real problem appears when you shorten it) or solder it to a metal rod or plate (that can be easily hidden as any submarine antenna or rail) and get the proper range without any interferences.

In fact, this "solder the antenna to a metal rod" tip can be found inside any WiFi router or WiFi laptop, whose antennas go from the WiFi board to an aluminium plate bolted right behind laptop screen.





You can see it on Nintendo NDS too, where the antenna wire is soldered to a board that contains a "printed antenna".





Hope this helps.

Cesar.
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Old May 12, 2013, 08:47 PM
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there is a lot that can be done with the stock 33mm antenna. by the way, 33mm is only 1/4 wave. a full length antenna is in the area of 12 cm.
i messed with this a while back, replacing the antenna in a r610 with a length of SS wire. got conflicting results. some better some alot worse.
for me teh problem with the length of the wave. trim a CW 7mhz antenna 1% and you cut off 8 inches.
trim a 2.4 ghz antenna 1% and you cut off 0.12 mm, or in the area of 0.005 inch.
but there is a lot u can do. the antenna sucks bad. a dipole would be cool. run lines fore and aft and have a working 'scale' radio antenna on a micro sized type VIIIC.....
that 1/144 scale type VIIIC looks mighty tasty right now.....
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