If you hear a buzz on the short term hire frequencies, then it's pretty well going to be digital. However - you must remember that rubber duck type aerials really mean VERY short range comms. The tree, in full foliage will attenuate signals, but I suspect they're not there in the first place. All the adverts for radios that even mention a range should be laughed at. Range is entirely context based. You can get accurate software that will let you enter an aerial, the frequency, the aerial's gain, the height above the ground, and then the same for the other end. It calculates path loss in dB, and if this is within the capability of the equipment, it pretty well works. Remove the aerial from the high clear point and drop it down to your window sill, and if it's a rubber duck type then it's total luck. For example, where I'm sitting, I can hear loads of marine users - as despite the trees, the sea is 1 mile away, downhill. I work from home for a decent amount of time, and in my studio at the rear, I hear absolutely nothing! The RF trying to go through the house.
Loads of posters on here say simply they cannot hear anything - and the solution could be really simple, but we don't know your geography.
First question - is there actually any local radio activity to hear? Do you see people close to you with radios. If their radios work outside your house, then yours will too. People using hand held radios just a mile or two away may simply be too far away unless you install bigger outside aerials. If you live within half a mile of an airport, then you will hear loads of things. Move to a mile, and you lose lots. Move to ten miles and you hear the planes flying overhead and probably you cannot hear the tower. You might hear the approach, because this often comes from somewhere else, aerial wise - which could be nearer to you, and they are usually more powerful ground stations. If you live in an area with hills, or worse, mountains - then living in a valley is bad news. The general rule being that if you can see it, you can hear it. You can hear the astronauts in the space station when they are overhead on your rubber duck aerial, yet you cannot hear something much more powerful, if there are obstacles between them and you. If you can get a topographic map, you can often predict the best directions for your reception.