There is, on the radio/com screen of the HDX. It will control both radios, but, as always in an aircraft, only one radio can be actively selected at any given time. The Top Bar is a status display that appears on all (I think) HDX screens. It displays track, altitude, etc., along with the frequency set into whatever radio is selected. If you have two Dynon radios installed, they will both be accessible and controllable via the radio (com) screen on the HDX, but when you exit the radio screen, only the status information of the currently selected radio (frequency, etc.) will be depicted on the Top Bar of the screen. You'd have to go back to the radio screen and select the other radio to make it display in the Top Bar. Additionally, in a two radio setup, when viewing an airport on the HDX (not on the com screen), using the TUNE or APT-COM buttons only sends the frequencies for that airport to the primary radio, not to the secondary. You can still go to the com screen and and send those frequencies to the secondary radio from there, just as you do with the primary radio. If there's some part of this I'm not being clear on, please let me know. Sometimes I don't get what point isn't coming across to other people. But in a nutshell, both (Dynon) radios are fully controllable on the HDX, or from dedicated radio knob panels. I plan to control them from the HDX because my panel space is limited. Because my third radio will require the use of a PMA7000, I can select radios from there as well.