Was referring to a simple 2-port router, no reason why a router couldn't have just 2 ports which some do but they are no where near as common as the 1-port models.
Absolutely right - no reason at all AFAIK, provided the two ports are built into the router. I was thinking about an add-in hub/switch, which is - only in part I know and as a non-preferred solution, albeit the only available one AFAIK - what you mentioned. In this context a 2-port hub (ie one port in and one port out) wouldn't add much, aside perhaps/possibly for some extra packet processing.
Who's 3G router are you using?
The one I'm using is a MultiTech Multimodem GPRS (not sure if this is a current model any longer with an Ethernet interface - it is 3-4 years old now.) And yes I know plain GPRS isn't very fast, but it's fine just for passing the small per-minute amount of WLIP data.
Actually, for all the talk about minimising power drain from an additional hub/switch, it is the GPRS/3G router that is the real power hog. But I guess if it's going to be radiating up to 2W of RF power then several different makes/models of router are going to be wanting much the same power overall of 3-5W depending on frequency band, because it's the RF transmission requirement that dominates the power consumption and not the rest of the circuitry. Two things I wonder about:
1. How much it might be possible to reduce average router power draw by using a high-gain yagi antenna for the cellular signal. Aren't 3G routers supposed to be clever enough to limit Tx power according to the strength of the signal from the cellular base station?
2. In the context of eg the WLIP, which only needs to transmit data every minute, is this long enough for the router to send its cellular Tx circuitry to sleep and then to set up the connection again when data needs to be passed. So is it worth looking for a router with an auto-sleep function (assuming that they do exist) and would this work OK with a WLIP logger?
BTW I don't know whether Admin is likely to read this post, but I'd be really pleased to see a forum/subforum set up dealing specifically with remote wx sensing - ie just the sort of topic we're dealing with here - it's a topic that's not really covered much elsewhere and can be tricky territory for anyone interested in setting up such an installation who is not already an M2M professional.