Yes you'll want clear line of sight between the "internet connected" house and each of the others.
5GHz (a/n) is usually better for the outdoor links between buildings as long as there are no trees / branches in the path so choose your mounting locations carefully.
To link 3 buildings, you will need 3 or 4 radios depending on layout. If A has internet:
C << A >> B
needs 2 radios at A (or an omni but these pick up more interference than a directional antenna)
A >> B
A >>>>>> C
might only need 1 radio at A (if B does not block the path to C)
These will work well and at 300m you won't need anything like their maximum power:
If you can find the smaller Loco M5 somewhere in stock, they are a little cheaper but otherwise the same innards
(just a slightly wider beam pattern which won't be a problem at your quoted distances.
They have MIMO data rates up to MCS15 (300Mbps over-the-air signalling rate - real IP throughput up to 150Mpbs half duplex (i.e. like 90/60 or 75/75). Try to create your links with signal to noise ratio of 20dB or better. On ours we tend to aim for MCS 12 at a minimum.
If you have line of sight and you make good links they won't add noticably to sat latency - maybe a few ms at most.
In a standard setup these will form a transparent (layer 2) link so you treat them much like long ethernet cables once up and running - i.e. they can be used to extend a LAN across buildings.
But in their web GUIs you have additional options such as for client isolation, adding firewall rules or traffic shaping or run one or more as routers (as opposed to bridging). Linux kernel - so as well as the GUI you can SSH into them or customise the config further,
Power wise they use at most 12W (maybe at boot up) and falling to around 8W or less in normal use).
Being outdoor radios these are weatherproof (come with PoE bricks so supplied from inside each house)
as with most outdoor units they should be mounted vertically with cable emerging at bottom, and a drip loop if the cable rises above the base of the unit before it enters the house. They can be painted for aesthetics (but cover holes before spraying!).
Indoors for device access you can continue use standard wireless (if routers, ethernet / cable type rather than ADSL)
prompt $P - Invalid drive specification - Abort, Retry, Fail? $G
prlzx on n e w n e t: ADSL2+ / 21CN at 3.5Mbps / 800kbps
Edited by prlzx (Tue 20-Nov-12 21:38:32)