Darn, any clue if there's anything to tune on a discone or any tricks to possibly increase the range? I am up as far as I can go in my attic.
As Jon said, getting it outside and up higher is important.
Most of the frequencies you will listen to travel line of sight. If your antenna can "see" the transmitter, you'll likely be able to hear them. If there is mountains, hills, large buildings, etc. in the way, you'll have issues.
Since discones are low gain antennas, they really don't do anything more than pick up what's there and pass it down the coaxial cable. They don't provide any gain, directionality, etc. The only real benefit to a discone is that they are extremely broad banded.
By getting your antenna up higher, the radio horizon will be farther off. Also, almost all building materials have some RF attenuation characteristics, so you are losing a tiny bit of signal due to the plywood and roofing materials (you don't have a metal roof, do you?).
One other thing you can do is to use lower loss coaxial cable. Since all coaxial cable has some loss inherent to them, and that loss is multiplied by the cable length. To overcome that, you either need to shorten your coaxial cable run or use higher grade cable.
Other option is to use a pre-amplifier mounted at the base of the antenna. These boost the received signal at the antenna and increase what's sent down the cable. It's not a "free" solution, though. Amplifiers can increase nearby signals so much they'll overpower the receiver. Think being at a loud party and trying to listen to someone across the room whispering. Amplifiers also increase unwanted noises.
Sounds like it's actually working pretty well given what you've got. Just be careful, chasing those far off signals can get expensive, time consuming and dangerous.
