No, I'm afraid you still don't understand. Any packet-switched radio, is digital by definition. Not "can be", but "is".

Radio, any RF transmission, is analog by nature. But the information you send has to be encoded somehow. You can do that in an analog manner, such as AM, FM, PM methods. Or you can do it in a digital manner: ASK, FSK, PSK, etc. Packet radio used by hams uses AFSK, as did early dial up modems you talk about, and both are a manner of transmitting a digital signal over an analog channel. Go look it up on Wikipedia if you don't believe me: packet radio and modems. Both pages very distinctly state that these are methods for transmitting digital data. Also mentioned in the original post was APRS, which is also specifically stated as being "an amateur radio-based system for real time tactical digital communications."

If you are sending packets over your radio, you are sending digital data.

Umm... you are aware that packet radio IS digital, right?

Pointing your antenna straight up is exactly the worst thing to do in this situation. The type of bipolar antenna most routers come with are omnidirectional, but with weak spots in the coaxial direction (directly out the two ends of the antenna). You would do better to turn your antenna sideways (horizontal) to broadcast in the "up" direction. The problem then is that you are also broadcasting sideways and down, so the up direction gets about 1/4 of total output power. What you really want in that situation (basement installation) is a parabolic antenna pointed upwards. They have very good gain (3 dBi or more) in the forward direction, while rejecting most signals from the sides or rear.