Jee Labs Talk

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1. raalst
   

   I know you can graduate in antenna design, and I did not. what I need is an extention cable of about 50 cm (20 inch) between the hopeRF chip and the antenna.

   I understand that coax cable is used for that, but there are all sorts of coax. preferrably I would use thin, flexible coax. also, I understand you might need to place a resistor on the end of the cable ?

   I hope that someone who reads this is knowledgeable enough to help me on my way. all tips greatly appreciated !

   Why do i need this ? because the Jeenode will be in a submarine, enclosed by water, the antenna should stick above water in order to be able to transmit. I intend to disguise it as a periscope.

   ok, back to studying antennas and antenna cables, in the meantime thanks for your help !

   Posted 06/06/2010 11:47:48

2. bvwelch
   

   This sounds like a really fun project! I'm not an antenna expert either, but RG174 is a small coax that might work. At the top (above the water), you may want to try a 'dipole' antenna- two wires instead of one. Or put something up there to function as a 'ground plane'.

   Posted 06/06/2010 12:28:47

3. raalst
   

   I molested a wifi antenna, to discover it s no more than a bit of coax with it's sleeve rolled back a few centimeters, exposing the core the same amount of centimeters. this is a dipole and it can be hidden in the periscope easily. I am hoping that the water surface will act as an extended ground plane.

   To be fair, this part of the development needs a lot more study and experimentation on my part. The antenna of the 40 Mhz r/c receiver is usually stored inside the watertight compartment of the sub, crumpled up and next to a (servo) motor and speedcontrollers, violating about all antenna theory, and still works OK up to 3 meters deep....

   Posted 06/06/2010 13:21:23

4. tankslappa
   

   This sounds like a fun project, I'm fascinated at what you have planned for your submersible menace.

   Just remember, I'm sure there are laws against torpedoing ducks and fishermen!

   Can you make it look like this?

   RCNautilus.html>

   Posted 07/06/2010 15:31:59

5. raalst
   

   the big plan is to build a model of an italian midget sub. I did create the hull already. it has a relative large periscope, which will be above water at all times. I think I have found a way to construct a simple directional sonar. that info should be sent to shore. I just ordered an antenna which looks conveniently like a periscope top... No torpedo's (in version 1.0..).

   more info on the hull : I'm not the fastest builder, as you might notice ;-)

   19th and 20th there is a big meeting again, in Mol, Belgium. some video can be seen here :

   Posted 07/06/2010 19:46:55

6. tankslappa
   

   Blimee, what can I say to that except "WOW!"

   Far too much skill and patience on show there!

   Posted 07/06/2010 20:21:55

7. raalst
   

   thanks, but it is mostly perspiration (and meddling in things you do not fully understand). At least, with submarines you know when you made a mistake ;-)

   btw, for londoners, this might be interesting : next sunday, St Albans

   From now on I'll stick to electronics on this forum. promise !

   Posted 07/06/2010 21:55:51

8. tankslappa
   

   Ooh, that looks interesting... Any room in the tank for a silly photographer? :D

   Posted 08/06/2010 01:38:38

9. raalst
   

   probably yes. if you are serious about that, email me at raalst at gma1l dot c0m (you know what I mean) and I'll forward your question to the organizer of the event. if you can make underwater snaps, you will probably be very popular !

   Posted 08/06/2010 15:36:23

10. tankslappa
    

    Unfortunately only semi-serious this year... I won't have my PADI photography and waterproof camera case in time (you don't want to know how much those cost!).

    Maybe next year, it'll certainly be a change from pics of coloured fish, and I doubt many of the others would have been a submarine recovery diver :-)

    Posted 08/06/2010 16:02:02

11. raalst
    

    No problem. you're still welcome as a spectator anyway.

    JC, could you maybe remove the last posts as they do not have an awful lot to do with electronics...

    Posted 08/06/2010 19:03:07

12. jcw
    

    No worries - bits are cheap. Besides, I kind of like the submarine links in there!

    (if only the whole internet had the signal-to-noise ratio we're achieving on this forum... :)

    Posted 08/06/2010 20:35:33