USA version: The frequency range of these units is 537.0 to 558.6 MHz. These frequencies are shared with USA UHF TV channels 25 to 28. TV stations have room-sized transmitters that may produce an effective radiated power of one million Watts. Wireless microphone transmitters produce a mighty .01 Watt, for the most part. The inverse-square law is your friend, but be realistic. :) Consult the FCC DTV Reception Maps for your intended use location, and you will find reference received signal strength for the TV channels there. (Note that the displayed channel number is usually NOT the actual RF channel. Click the station on the list, and the truth shall be revealed.) To minimize interference, pick your wireless frequencies in the TV channels with the lowest reference signal strength. If you're using several wireless systems, the rule of thumb is to allow at least 1 MHz between channels, and space them irregularly to minimize intermodulation issues.Quirk: The F20 units have a quirk. I currently have four pairs, and this is present on all four. The "topping" part of the charge cycle seems to take a loooong time. If you want these fully charged, let them go overnight, or even longer.

Great product thank you!

No regrets,they work great for me. No more cable to ny mic preamp, game changer.

My first unit stopped working, but the seller was responsive and sent a replacement no questions asked, so far the replacement has been working well for several weeks. This is the kind of thing that makes sound techs either breathe a sigh of relief or develop trust issues. Fortunately, this one falls in the not garbage category. The 150ft range is no joke, and it holds a solid signal even when surrounded by other RF devices. Works well for dynamic and condenser mics, which means fewer cables running across the stage for people to trip over. Ideal for anyone who’s tired of untangling XLR snakes at the end of the night.

I purchased 4 sets. They all work well. Plenty of Battery life, and range. I use them for video recording. Sound is very good.