What are the repercussions of using 2 transmitters on same frequency? Tx are ~50 feet apart and the freq is 447.800 mhz.
In the simplest case, the result will be useless. It's like having two people with identical voices shout at your simultaneously, except that radio receivers are even worse than human brains at separating signals.
If you want to have multiple transmitters operating simultaneously, you need to multiplex them somehow. There are many ways to do that. The simplest way is usually to put them on separate frequencies. This is precisely why companies that make money on wireless communications exchange a lot of money for the right to use a frequency.