Right. So, if the coil really is 4.87 millihenries, then that's way too much inductance for frequencies around 50 MHz. The coil will be well above its self-resonant frequency. The current and voltage in the coil will form standing waves (or worse, traveling waves), and there is no possible way to have a uniform field.
At 50 MHz, the free space wavelength is 6 metres. If you want a uniform field, then the total amount of wire in your coil will have to be much less than the wavelength, at least by a factor of ten, and probably more. So, your coils would have to be wound with no more than 0.6 metres of wire. If that's not enough to give you the size of coil that you need, then you would have to use multiple coils, and feed them in parallel.