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post #177 of Old 01-29-2011 Thread Starter
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Originally Posted by mlahrkamp View Post
With all due respect to all particpants: This thread was originally suggesting (from my reading) that a 12dBi antenna was going to be superior to, say, a 6dbi because it had more range.

Max power allowed is 36dBm for Wi-Fi (for Point-To-Multipoint). That's a full power Bullet2HP and a 6dBi antenna. Staying within the 36dBm limit, a 12dBi antenna coupled to a Bullet would need it's output power derated to 24dBm (250mW). It would seem the benefit of increasing the antenna gain is significantly reduced, if not eliminated, by the decrease in power output of the radio. What you end up with is about the same range and a pancake of a radiation pattern. Why not just stay with the 6dBi and enjoy a fuller 'donut'?

Of course, there are those that would (whether intentionally or not) couple a full power Bullet2HP to a 12dBi omni (42dBm, 16W output). The result is overdriving of the input of the hotspot receiver if in close enough and polluting the airwaves for everyone at an anchorage or marina. Tests we've run and from what I've already read in this thread suggest this is happening. Now at distance: The problem is that the hotspot is probably running only at 36dBm (4W) and may hear a distant 12dBi system, but the distant 12dBi system can't hear back because the hotspot is putting out 4x less power. My arguement (from our tests) is that the Bullet (with stated sensitivities) having a 12dBi antenna stuck on it does not increase its ability to receive to the same order of magnitude as its ability to transmit. Ergo: different effective real world transmit and receive gains. We have successfully connected in excess of 5sm using a 6dBi omni and Bullet2HP mounted on a radar arch (with a clear line of sight and a properly powered and located hotspot of course).

If you want a reliable connection to those distant hotspots that seem flakey, increase the sensitivity by selecting B mode where the spec for the Bullet2HP says that sensitivity and output power are highest. There is also the benefit with lower data rates to receive more reliably since each bit slice time is longer thus giving the receiver a greater opportunity to properly detect it.

This is not about believing/disbelieving anyone. It's about being a good netizen (net citizen) and sharing a Wi-Fi resource that should be available to be enjoyed by all in a marina or anchorage.

Again, if anyone has any real world experience that suggests any of what I've stated above is faulty, I'm alway open to listen and potentially change my viewpoint.

(Just re-read this.)

I didn't know this before Mike posted about it. One minor correction I'd make....

Having a high gain antenna will help the receive signal strength, so you'll be able to recieive signals from farther away from the marina or other access point. From what Mike says, after connecting a high gain antenna you would lower the transmit power. And doing so won't matter to you because you are limited by your receive signal strength. And you'll be a good netizen too.

This means that with a high gain antenna you could buy a cheaper bullet that doesn't have 1000mw (1 watt) of transmit power. If I recall correctly, the 250mw ones are much cheaper. Even the 800mw ones are cheaper.

As for me, since I like to experiment, and I don't mind making the setting changes, I'll keep the higher power one that I have and lower it's power output. Some experimantation is in order to find the sweet spot of lowest power without affecting performance.

WiFi is designed to serve multiple poeple at once. We don't want sailboats to get a bad reputation by "stepping on" the signals from others. Please transmit responsibly.


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