I think that some of it may be down to the transmitter.

I could run my Tiger to about 100 foot without an aerial on the tank. But one day I dropped the transmitter and it smashed, no problem, I thought, I've got others. But my three other transmitters will only work to about 50' even with an arial on the tank.

It's not really that much of problem because I don't run it that far from myself (I'm too lazy to walk to it if it gets stuck).