My favorite hand-held controller is my Turnigy i10 (also known as the FlySky i10). It works great, but I needed more range. Adding boosters is a hassle, and the radio does not accept standard FrSky transmitter modules, so I decided to design and build a repeater. My repeater is a small (2.75" X 2" X 5") 3D printed box that has a “pocket” that accepts FrSky modules. It uses 3 X 18650 cells for power and has a voltmeter readout of battery voltage.
Now I can insert either a 915Mhz or a 433Mhz transmitter module (up to 1 Watt - since I’m a “HAM”) and I get incredible range, and I can still use my i10 radio. The latency through the repeater is negligible.
I’m currently using an IMMERSION EzUHF 433Mhz setup.
If anyone wants the 3D model and the connection diagram of this, PM me and I’ll send it to you.