How do you test your antenna idea? Well, our approach was to get a portable network analyzer that can show received dBm, put a commercial antenna on it, and strap the whole thing to a PVC pipe (for insulation and to get repeatable height). Then, zip-tie a cough drop to the PTT of a walkie talkie set to low power, so that it transmits continuously.

Now you can walk around your contraption with your Drain Pipe of RF measuring, and get a (rough qualitative) idea of how the pattern looks like. Much to my surprise, it actually worked.