IR Receiver for multiple frequencies - IR extender

I need to build a IR extender and to make it compatible i wonder what kind of receiver i need for
30 KHz, 33 KHz, 36 KHz, 38 KHz, 40 KHz and 56 KHz.

I have a MX-780 Remote Control that can receive 15kHz to 460kHz:
http://www.universalremote.com/product/mx-780-remote-control/

I wonder what they use inside that remote?

Also if i look at this Vishay document there is AGC1, AGC2, AGC3...:

Nobody?
Also the cheap IR repeaters from Amazon work from 34 – 60kHz...

But if i look for TSOP receivers they all have a fixed frequency.

you don't typically use an IR recvr (like the TSOP series) for extenders ( the TSOP's decode/demodulate the received signal). You use IR photo detectors OPamp drivers and IR LED emitters.

The commercial extenders I saw are only ~4 meters (13ft) and i need ~10 meters (33ft).
Since one side already has a Arduino the idea was to use another one on the other end
and pass the signal over RS485.

I had the IRremote library in my mind. But after your posting i think decoding is not needed?

So how to accomplish this task?