Build your own 900MhZ antenna.

thingiverse

Why waste money on the "immortal T" 900MHz antenna and wait for it to arrive from China for a month when you can build your own? After all, the famous "Imortal-T" by TBS isn't as immortal as it claims. Mine broke down before my first flight with massive fail safes at 50 feet. The Imortal-T is weak in design - try grabbing it by the top and spinning it, and you'll break it immediately. The joint of the two radiating elements should be covered with epoxy before encasing it in antenna housing, which they failed to do. All you need is a rubber ducky antenna or an FPV video antenna that you no longer need and two pieces of 83.3mm copper wire to make a dipole. Solder one part of the radiating element to the positive (center wire of the coax) and another to the ground of the coax. Use some antenna tubing to protect the wire from bending. With an RF Vector Analyzer N1201SA, I was able to tune it exactly to 900MHz with an SWR of 1.2 by clipping the ends of it. Then I designed this housing to make it truly indestructible. The SWR and tuned frequency will change with housing, tubes, and rubber end-caps, so adjustment is needed by clipping the ends after final assembly. Very small increments need to be clipped as you can go from lower to higher frequency but not the other way around. If you pass the desired frequency, then the antenna is no good. Download the STL file and print two of them with openings facing down - no supports are needed. Good luck!