Hope im not in the wrong forum guys but here goes. I know you cannot use 2 separate repeaters on the same RX and TX.
Sure you can. I see it done all the time. So long as users understand the system, particularly it's drawbacks, it can be exactly what's needed.
But, in certain fire districts in our parish the transmission is very poor. Can I take and have a secondary repeater installed with a different recieve frequency and set it to transmit to the recieve frequency on the primary repeater. But yet still allowing the RX stay the same on the department radios.
Yes. This can be done, but it's not how I would do it.
You can put up multiple repeaters, on the same input and output pair. Use a different PL tone for repeater access, but transmit the same tone on each repeater transmitter so the mobiles will hear any of them. Change PL tones on the mobiles or control stations to access different repeaters.
This technique works very well, and is widely deployed by CalFire and USFS here in California.
Several have said this cant be done because u cant use 2 separate repeaters together. or they may not be competent enough to give me a straight answer.
To be sure, there are drawbacks. If you want to go cheap, the technique above works well within it's limitations. If you want to tie the repeaters together, then there is several additional layers of expense and complexity involved. But it CAN be done, and can be made to work extremely well.