Hi John
An interesting article. I noticed that although the writer discusses that the PVC didn't get hot in his microwave oven (inicating it's not lossy), the detuning effect of the PVC dielectric isn't discussed. This was one of the major problems I had when using PVC pipe as a former. If you can take the dielectric effect into account (assuming all PVC pipes have the same dielectric properties), then great. Another common fault is to use a non-central support.
Had I known the above tips, I would have saved myself weeks of fruitless efforts!
Helices are very forgiving antennas in general. The things to pay attention to detail on are the former and the matching section if you're interested in picking up weak signals.
One further thing - the amount of RF at 2.4GHz now that wasn't there seven years ago is astonishing. The pick up from sidelobes of the helix may make performance disappointing for satellite use.
I have a number of articles on building helices including:
http://www.g6lvb.com/60cm.htm#PerfectHelix http://www.g6lvb.com/quadruple_helix.htm
Cheers, Howard G6LVB