Bets51,
Good questions. I’ll give you my view on each use case in turn:
- Paraphrasing, the first use case is: “Communicate while in two separate cars following each other in close proximity.”
This is viable, as long as there is a passenger doing the messaging! 
Be aware that radio transmission and reception from inside one vehicle to inside another is poor because of the surrounding metal cage that is the frame and body of the car. Thus, the viable distance for highly reliable radio-messaging is short because you are in a structure that interferes with radio transmission. In my experience, you’ll want to be within a few tenths of a mile of each other for good results. Also be aware that it will be problematic if you don’t have a good line of sight (through the glass car windows) from one goTenna Mesh device to the other. The obvious way to improve the effective range is to mount the goTenna Mesh devices securely on the outside of the vehicles, but that will require preplanning to have a secure way to mount it, and it still may not be viable in hurricane storm conditions that you mentioned for this use case.
- The second use case is: “To be able to communicate with our granddaughter in CA if there is an earthquake. So it would be FL to CA.”
This is not viable. Why not? …
Simply put, the goTenna Mesh protocol puts a limitation on the number of “hops” that will be executed for a message, and the viable distance per hop is nowhere close to the distance needed to permit communication between Florida and California.
A more thorough explanation is:
Long term, the basic capability planned has been established as a maximum of (3) node hops for a message. Users who opt to subscribe to the goTenna “Plus” service will be granted an additional (3) hops, for a maximum capability of (6) node hops for a message. Currently (and only temporarily) the goTenna team has enabled a maximum of (6) hops per message for all users, even if they don’t subscribe to the “Plus” service. This has been explained on this community forum as a means to thoroughly beta-test the (6) hop functionality.
Without getting too technical, there is a practical limit to the number of node hops that can be supported on the finite radio band available to the goTenna Mesh product. Increasing the maximum number of hops permitted decreases the performance of the Mesh and its delivery success rate.
The shortest distance between Florida and California is approximately 2000 miles. Thus, the (6) hop limit would mean that each node hop would need to cover a distance of just over 333 miles - that isn’t feasible for 1-watt radio signals on the 900 MHz frequency band used by the goTenna Mesh. The maximum reported distance for a successful 1-hop (point to point, line of sight) goTenna Mesh transmission is approximately 50 miles, and under varying environmental conditions and topography it is usually much less. (Usually, it’s between 0.5 and 5.0 miles). Thus a more reasonable expectation for the effective communication distance in wide open spaces with flat topography and good line of sight is perhaps a maximum of 5 miles per hop x 6 hops = 30 miles. This also assumes that there is adequate node density across the area from the point of origin to the destination - a condition that won’t exist in most places today. (That’s why we need to mesh the world!)
- The third use case is: “To be able to communicate when we go overseas back to the US as well as between each other if we got separated from each other.”
While overseas communication back to the US is not viable for the reasons explained above, it is viable to communicate between separated travelers in the same vicinity - this is a very practical application of these devices.
So in summary, a practical expectation for the day-to-day communication distance using all 6 available node hops in optimal conditions is (arguably) around 30 miles. Under poor conditions, 6 node hops might only get you 3 miles, and under wildly optimistic ideal conditions, 6 node hops might get you 300 miles - but I wouldn’t count on it!
