Antenna for ACARS and listening to ATC with DVB-T dongle

Hi,
I already have an FR24 feeder (F-EGNT4) which I obviously use for feeding to FR24. I recently purchased an RTL2832U+R820T DVB-T dongle. I wanted to use this mainly for picking up ACARS messages. As expected, using SDR#, the acars transmissions that I receive are very faint and no decoding software can decode them (even whilst using a large amount of gain) whilst using the stock antenna.

I don't know a lot about antennas, which is why I asked here: I am looking for an antenna that could let me pick up these ACARS transmissions so that I can decode them. I don't mind making the antenna or buying one as long as it is reasonably priced. I also don't mind whether the antenna is inside or outside. If I was going to go into the bother of mounting it outside, I would rather that it could pick up ATC transmissions as well (however, if this will decrease the range of ACARS transmissions I can recieve, please let me know). Finally, if I do mount an antenna outside, will it need any spacing from the FR24 antenna that is supplied with the reciever?

I would like monitor ACARS frequencies: 131.725 and 131.525 (not necessarily at the same time)

Can anyone suggest an antenna that I could buy or make?

Thanks
- WeKnowMC