I have an FM transmitter I purchased a while back (Car And Driver 4057 Bluetooth FM Transmitter), and I've been wanting to boost the signal length but I'm not really sure as to how, right now it transmits maybe ~5-6ft and I'd like it to transmit 10-15 maybe even 20-30ft to overcome any interference. I've found a test report that is pretty helpful, but I'm not sure as to how I'd extend its signal length.
Test report: https://fccid.io/2AMSOCAD-4057/Test-Report/Test-report-3886714
PCB images: https://fccid.io/2AMSOCAD-4057/Internal-Photos/Internal-photo-3886708
Test report: https://fccid.io/2AMSOCAD-4057/Test-Report/Test-report-3886714
PCB images: https://fccid.io/2AMSOCAD-4057/Internal-Photos/Internal-photo-3886708