We tried something similar many years ago. Got a surplus weather balloon and attached a small dual band amateur walkie talkie. Set the walkie in cross band repeat mode and raised it on the teathered balloon. Worked great, but was quite expensive to purchase the gas.

Then we tried it on a para-wing type kite. A rather large one. This worked better as no gas was needed. In both cases we tried to raise a long wire antenna and the weight of the wire (super flex antenna wire) was too much. The walkie was a bit lighter, but I think it had something to do with the way the wire loaded the balloon and kite. Sagged quite a bit. I keep a kite in the camper now. Hmmmm that was fun to do. Think I will try it again now that I have more time to play with it. An advantage of being retired.<smirk>