If you are anywhere near a handful of FM broadcast stations (88 Mhz-108 Mhz) 9 times out of 10 they are going to cause some serious inter-modulation (mixing of signals) if you raise the RF Gain of any radio. You have two choices. Live with the mixing of signals or use a FM-Notch band reject filter.
I have used FM Notch filters from Mini-Circuits, PAR, MCM Electronics & Radio Shack. I have 20+ stations within 10 miles of my QTH. (Left Pic).
The Par units are very effective but super expensive. If you go with the cheaper MCM/Radio Shack brand you will most likely need to run 2 units in series to really notch the FM band effectively.
Going on one of my late night E-Bay strolls I came across a FM-Notch that was small, inexpensive & from the specs looked to be almost to good to be true for the price.
This unit is a semi-kit. The only parts you need to solder are the provided slotted SMA ports. Below are some before and after waterfall screen shots. This FM bandpass filter is without a doubt the best bang for your buck ($24.00)