frequency.
Q3:How to choose antenna for transmitter?
Usually we need to check the maximum RF power that the antenna can afford, then use the antenna with transmitter that broadcasts at or below the antenna MAX.RF Power.
Q4:How many frequencies can I use in one transmitter?
Most of our transmitter are in normal FM frequency band(87~108mhz), you can change to any frequency within this band. Use one frequency at one time.China Fm Transmitter
website:http://www.besttransmitter.com/fm-transmitter/