40 miles with an indoor antenna, depending on the terrain and frequency, might be pushing it. You would have somewhat better luck if you can get it higher, say in an attic, as clear of obstructions as possible. A beam is your likely candidiate, such as the Grove scanner beam.
mainy 100's & 400's Mhz I'm looking for a WB antenna that gives me the best all around coverage. I live about 3500 feet above sea level and about 2000 ft above the city, with no obstructions of any kind facing south towards mexico. I saw a base discone antenna that was for indoors, however I wasnt sure how good it was. It was about 3 feet in height. I'm looking for something easy not because I'm lazy, I was injured in Iraq and installing an antenna up high is just impossible for me to do. I was thinking about sticking an outdoor discone antenna on about a 6 pole outside to at least give me a beter chance to pull in more traffic.
Indoor antennas are the worst. Outdoors you will hear fine. Indoors, you'll pick up your toaster, your electric blanket and any number of other appliances inside as noise sources. Use your air conditioner to mount a mag mount antenna and you'll be better off. I have antennas both inside and outside, those outside work much better. Again I say, there is no best antenna indoors.