Hi Fire and all,
Ah the old familiar ground plane, I've made more than I can count. I've used an SO-239 flanged chassis mount connector and 5 pieces of 1/16" diameter non fluxed brazing rod as it's stiff and won't turn into a pretzel in the wind. The article says coat hangers but they rusted quickly although this doesn't matter with an indoor installation. Outdoors it's advisable to waterproof the center insulator with a big gob of silicone bathtub caulk and wrap the connector assembly tightly with cheap black vinyl tape, the "quality" stuff doesn't stretch well and won't wrap tightly for a good moisture seal.
A note on final assembly and soldering, put a 90 degree bend at the radial ends so they fit properly into the holes in the flange. Fasten the connector and radial temporarily but firmly, it shouldn't move during soldering or you'll get a poor connection. A dab of liquid or paste rosin flux (not acid as used for plumbing) will facilitate the operation. Use a big horse's leg iron that won't cool when it contacts the work so it goes faster and you won't overheat the work. I don't recommend a soldering gun, those things are pretty useless because the tip cools and tends to stick to the work or you have to hold it on so long it overheats the work. The key is speed, if it takes longer than two seconds to form the joint you've messed it up. When the soldering is done turn it upside down, put it in a vise and file the tips and excess solder off nearly flat leaving just enough to hold things together.
Outdoors an ordinary TV antenna mast is a good way to go, shove the coax and PL-259 up through the center before final assembly and the antenna sits nicely on top. Indoors it's own radials will support it rather well unless you use copper wire, not recommended in any case.
Last but not least for receiving only it doesn't matter if the radials are 90 or 45 degrees off axis, that only affects the impedance and SWR slightly on transmit. If you choose 45 degrees of course you'll have to hook the radial ends accordingly before soldering.
My two cents worth on the coax is avoid Rat Shack like the man said. As for the type, avoid RG-58, RG-59 and RG-8X being they're too lossy for VHF and up. Otherwise it needs no special consideration for "normal" runs around 50' or maybe a little longer, more than 100' you start to get into hard line and gain antennas.
OOPS! I almost overlooked the guy with the RG-6U quad shield! The trouble with that is it requires a special F connector which means a rather uncommon crimping die to put it on. More than that you'll have to use adapters which all in all isn't really a bad idea but more involved than necessary. It's better to use RG-8U type 1/2" cable for the PL-259 and an adapter on the receiver end to fit whatever is on it, probably the usual BNC female. You may consider a short flexible jumper of RG-58U there with a PL-259 on one end and a BNC male on the other to avoid straining and damaging the connector.
WHEW! I hope I didn't forget anything, my fingers are tired. (;->)
Good luck, it's nice to see a builder/experimenter for a change!