Total posts : 45366
Hi, RH –
Your Part 15 FM transmitters may be meeting Part 15 by allowing the antenna to radiate far less than the legal limit.
IMO, a Part 15 FM tx radiating the maximum legal field should be receivable on a decent receiver in most locations of a typical home with the construction you described — especially only 10 feet away.
As a test could you take it outside, and see how far away you can receive it over a clear path on a car radio? If it is not at least 200-300 feet then I’d suspect that your Part 15 txs are radiating considerably less than Part 15 allows.