Tom, operation from a townhouse or apartment will probably be a challenge, but my suggestion is just to keep experimenting with different configurations. Modeling is probably not real productive. Before I moved up to Alaska 50 years ago (with 3 acres in a rural area), I operated successfully from a townhouse and an apartment. But that was before houses were filled with SMPS's, etc. and propagation was much better. We travel often both in the US and overseas, and have operated from townhouses, hotels, HOA communities, etc. Often operation is not successful, but sometimes it was possible. In some situations it looked hopeless, but worked (kind of !). In other situations it looked an ideal situation, but no luck. Have used a #28 wire through window screens, some success. Also hooked onto a metal rain gutter, and worked a few adjacent states with 1 watt CW. Nearly 100 percent of my portable operation has been battery powered QRP CW from local parks, hiking trails, or even outside of a hotel or motel with a wire thrown up into a tree. RX noise usually drops off rapidly as you get away from buildings and electronics. Even 5 or 10 feet helps, and often a few hundred feet into a park, often the noise level drops to nearly zero. I have even operated from northern Norway and Alaska in the winter with temperatures below freezing. In the past I usually just used 1 watt on 40 or 20 meter CW, but with propagation so poor, I will probably go to something like a KX2 with its roughly 10 watt output for portable operation. My experience is that often (usually ?) you will not cause RFI with say 5 or so watts, but all bets are off with a 100 watt rig. In my house I set off my CO and fire detectors on 160 with even something like 50 watts, so since they were old, I switched to another brand....no problem, but who knows what will happen if I ever buy a linear amp. My antennas are about 40 feet from my house. Keep experimenting, and do give portable (or mobile) operation a try. You may really enjoy it. I sometimes backpack, set up a tent, and operate with 1 to 4 watts for 1 or 2 days. Rick KL7CW