Total posts : 45366
While AM will get you the greatest range, you’re going to have difficulty penetrating buildings to your AM receivers, particularly if they’re common consumer type radios (they have poor sensitivity and interference rejection).
One alternative is to build an intranet (or wifi local area network) using Part 15 wireless technology and use streaming to go to Internet Radios, programmed with the local IP address – a side benefit is potential access to the stream via smart devices such as iPhones. I’m currently experimenting with Engenius 7550 dual band access points/bridges (one band to provide connectivity to devices such as computers or smartphones, the other to link to other 7550’s). You can cover a large area with similar wireless devices (the Engenius just happen to be relatively inexpensive, approx. $150 apiece).
Another would be Part 15 carrier current. I don’t have much experience with that, but there are some here who do who I’m sure can give you advice.
