2.4 ghz above water antennae

[redboat219]

If one was to use 2.4 ghz onboard an rc sub you'll be pretty much restricted to running at periscope depth. My question is, how much antennae do you need stick out of the water, will the scale periscope height be sufficient?

[ober freak]

Re: 2.4 ghz above water antennae

2.4 GHz Rx antennas where build as 1/4th lamba with is 30mm. I think u need a minimum of 50% (15mm or roughly 1/2") should be above water. Haven't ever tried this, so it's up to you.

Marco

[KevinMC]

Re: 2.4 ghz above water antennae

I ran an experiment with a 2.4GHz set a couple of months back and found that the antenna could be completely submerged (although just barely) and I still got reception. For what it's worth I was using a DX-8 transmitter and receiving with an AR8000 receiver.

[ober freak]

Re: 2.4 ghz above water antennae

Was it in a bathtub or in pond/lake with several yards away from you? As I think the water surface also reflects most of the radiation at shallow angles.
Didn't tested this by myself, but a friend told me his powerboat loses the signal when it flips over (which happens mostly when it is far away on the lake).

[KevinMC]

Re: 2.4 ghz above water antennae

I did my test at our local running spot (a river actually) with the transmitter at a short but reasonable running distance from the receiver. I was trying to simulate actual running conditions as best I could because I wanted to know for myself what the limits of submarine ops from 2.4GHz actually are. (I've read plenty of "I know a guy who tried it..." stories but seen no accounts of anyone doing a first hand test. I'm not trying to diminish the value of your friend's report, but there's no substitute for a test you've planned and executed yourself.)

When the transmitter was immediately above the receiver I could actually get down to about 6" before the signal cut out, but since I wouldn't actually run that close I didn't figure it was a useful data point to report. It's reasonable to assume that had the transmitter been at extreme range that the useable depth before signal loss would be even less, but I don't have any data to support that.