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snooks

moving camera in covered swimming pool

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Heres one thats puzzling me (but not you lot hopefully) I have built a mobile underwater camera for swim training purposes and coaching. Camera below water video transmitter above (tried 2.4ghz and 1.2ghz transmitter and receiver combos but both experience the same problem) Fine whilst transmitter stationary picture is received crystal clear. As soon as the trolley assembly (above water at edge of pool) holding undwater camera on extension arm is moved the picture comes and goes with various degrees of interference. I suspect it is to do with the building structure which has steel roof, block walls, steel frame and glass walls (plus a lot of water of course!) causing multipathing with the standard stick aerials supplied. Has anywone else had or managed to overcome this type of problem. I've had to revert to a hard wired connection at present how crude and cumbersome! I have direct line of sight and max distance from transmitter to reciever is about 30metres max. Perhaps a patch arial or some shielding to give a type of directionality might be possible or the answer? Any help or thoughts would be greatly appreciated.

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Try very low power, also if the direction of both TX and RX remains simular then a patch aerial on both should work.

Aerials over head hight would be best.

What power are your transmitters ?

Terry

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Thanks Terry for coming back

I initially used GigaAir 2727 10 mw transmitter and receiver (2.4ghz)(could this power be reduced somehow perhaps?). These worked fine but with the interference as described before. Their built in arials are just normal omnidirectional about 5" tall. I then got a 1.2ghz from the far east (similar sized arials) with 1w of power (claimed) but result just the same. I was unsure which way to go so I wondered about patch aerials as described in the 'goof proof' article which is where I came across the RC-Cam site when 'googling' for an answer. Being a complete novice about RF transmission it has been a steep learning curve. Usually I will be able to acheive a clear line of site between tx and rx but I take point about raising both antenna above head height its one less interference to worry about I suppose. I just wondered if patch antenna on both transmitter and receiver might be too directional? I was going to try patch on receiver at first but any suggestions about either a supplier or making one myself would be welcome. I certainly don't need range or power to solve this it seems.

Kind regards

Edited by snooks

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Your problem appears to be due to multipathing. As you have discovered, more RF power is not a cure for that (and can sometimes make it worse). A diversity Rx would probably offer satisfactory results.

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I would have ago with the 10mW 2.4Ghz system again but try using the goof proof patch at both ends. The patch aerial will not be too directional, in fact it may still be too wide as the working angle can be as much as 180 deg but the gain dose drop off near the edges.

If you still have problems then lowering the output to 2 or 3mW will be your best bet. This can be done with resistors but I wont go into detail yet as I will have to look it up. Unless someone else can chip in with the correct way of doing it ?

Terry

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Thanks guys I'll start with the goof proof patch arials and see how I get on the diversity option looks a little more pricey unless any one can advise of a realistically priced(i.e. cheap!!) one. many thanks

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