I'm roughly 10nm south of VVNB (Hanoi Noibai). The stock antenna performs well on top of a 120m+ antenna mast which gives me excellent coverage of the airport, and mostly unobstructed line of sight to all other directions. It's no doubt a nearly ideal antenna mast, since the hotel bar on the 30th floor also supplies gin tonic. I'd like to install my radarbox there permanently, but that's another project.
I just tested the stock antenna for 24h at home, on a 4th floor terrace, surrounded by obstructions. Reception is still ok, roughly 70 nm for flights at FL20-40. I receive some random messages down to 1600ft around the airport, but reception is really only reliable above 5000ft. Polar diagram attached.
Todays project is to raise the stock antenna above my own roof using a 6m bamboo pole. I "weatherproofed" the stock antenna with some vaseline, and a childrens balloon stretched over the base and around the cable. A thingy which formerly contained fish oil capsules fits neatly over the top of the pole, I'm going to bolt the ground plane onto it. I'll mount the radarbox 2/3 up the mast, in a formerly airtight lunch box, again bolted to the bamboo pole. I drilled 2 holes into the bottom for the cables (and ventilation), and supported the connectors in styrofoam. 5m powered usb cable to a netbook from there. A 30 min build time antenna mast, ungrounded lightning rod, and static generator all-in-one.
Off to find nuts and bolts...hopefully I'll see somewhat improved reception. If not, I'll forget about mounting a permanent anteanna at home, and keep drinking gin and tonic...