Some marinas are practically blasting their signal out over the water and would be reachable at a couple miles. This is due to having outside antennas and perhaps directional antennas to cove a large sprawling marine with several antennas.
Houses, on the other hand have their wireless access points/wireless routers inside and this result in signal loss. Those antenna are almost never direction but are rather omni-directional. So they are reachable at a much shorter distance, maybe 1/4 mile.
The third option is subscriber access points. Timewarner Cable and Optimum Online/Cablevision both have coverage in our area. I have Optimum, so there's another "free" (I pay at home) way.
with some creative anchor locating, you should be able to pick up somthing.
Best thing to do is get the highest gain antenna that you can fit (12 db), use a Bullet2HP (1 watt version) that connects right to the antenna (no cable loss) and mount it high up (N connector rivited to the mast). I like th ePOE injector inside the boat near the base of the mast, so if/when you have to take the mast down it becomes a natural disconnect point for the wires.
Good info Brad. I've been using WiFi on a boat throughout the Caribbean, Bahamas & east coast US for seven years. Its only recently I've got around to having a long range system though.
I think way too much emphasis is put on the numbers & transmission strength of your setup. As its a two way thing, equally or more important is the sensitivity of your receiver & the gain of the antenna. Remember that many AP's you connect to will likely have less transmit power & a lower gain antenna even in marina's.
I've also found that the signal to noise ratio with any AP you are connected to is nothing like as important as the bandwidth of Internet throughput available at the AP's end. The actual "last mile" WiFi link will always have bandwidth way in excess of what's available coming in to the AP upstream, in all but worst case scenario's (i.e. weak 802.11b connection, lots of lost packets)
e.g. I am paying for access to a local AP running 802.11b about 200 yards away & am connected with a -45dBm signal. -50dBm (a weaker signal) is generally accepted as 100% signal strength, so its really blasting in, but the service although reliable is slow.
If I connect to another AP over 1km away using an 802.11g home router (I know 'cos I looked
I get a signal of -88dBm, only 3dB above the noise floor. However I get considerably faster throughput from this under used AP than I do from the local one despite vastly superior signal, accepting the occasional dropout altogether. This sort of comparison bares out time & again.
Obviously with a heavily used AP the available Internet bandwidth is only enjoyed by the strongest connections. In this case power/sensitivity does count else your at the bottom of the list for sending/receiving packets, but at other times it seems not.
To sum up, subjective assessment of throughput is what counts not numbers.