Unfortunately range is dependent on terrain. When including a radio module in a device the radio manufacturer quotes a ‘typical range’. This is commonly what people will quote. What they don’t tell you is that the expected range is only valid when the transmitting radio and receiving radio are located 50m above the earth, in clear uninterrupted air, with direct line of sight. This is sometimes achievable with drones but little else.
What I would say is take the typical range and then halve it for every obstacle between you and your mare. The radio module inside Smart Foal claims to have 1100m range.
So if you are on a hill, halve the range: 550m.
If there are a few scattered trees, halve it again: 275m. (If you have dense trees, divide by 4: 137.5m.)
If you have a car, truck, float or machinery parked in front of your mare, halve again: 137.5m.
If your mare is in stables, particularly with metal walls, halve again: 68.75m.
If you have all those obstacles you can see how the range quickly diminishes. If you happen to live on a football field that is perfectly flat with only grass between you and your mare then you can expect to get fantastic range, the rest of us need to be a bit more realistic.
This range indication is not just for Smart Foal but will apply equally easily to any other foal alarm. In fact it is a good rule of thumb for any device with a radio module in it.