... but this little 70 cm band ground plane antenna works beautifully.
As always, click to embiggen.
SWR is 1.2 to 1.15 across the band. The dimensions are 17.0 cm for the vertical whip (including the mounting sleeve on the coax connector) and 19.0 cm for the radials. Those should be the measurements for the bottom of the band according to MOUKD's online ground plane calculator, but the lowest SWR is at the top of the band. Go figure. In any case, with SWR < 1.2 across the band, it doesn't seem to be all that critical.
Construction notes: Keep It Stupid Simple. The elements are 12 ga solid copper house wire left over from another project, stripped of insulation. Had to whittle down one end of the vertical to get it to seat in the coax sleeve; a pocket knife worked OK on the soft copper. For the radials, the inner ends were bent into crooks that slipped through the coax panel mount's bolt holes. Used a solder stand with two adjustable clip arms to pre-position and hold parts for each solder joint. Nothing special, in fact it's a really cheap solder stand, but it more than payed for itself with this one project. Cut the elements about 1 cm long, and trimmed to length after soldering. Finished it off with a gob of bathroom silicon caulk to cover the center insulator and keep water out, but that's not shown.
The cost was nil. I see that these connectors go for $1.80 each over at Amazon if you're willing to buy a 5-pack. I had one laying around, so call it free. Scrap wire.... maybe $1? Again, it was laying around. So... somewhere between $3 and free for the whole thing.
Yes, the elements are a little wavey. They are scrap copper wire after all, and a 70 cm wavelength will barely notice. Taped to a yardstick and lofted to about 10 feet while standing on the porch, it reached the new repeater in Diamondhead very easily. Atop a 20' pole it should do even better, but that will have to wait for the weekend.
It's good to have access to a 70 cm repeater over here in the western wilds of Hancock County, especially one that is practical to use with an HT. Thanks to the folks who put this repeater up.
Rick Atkinson, author of the WWII Liberation Trilogy, now turns his attention to the American Revolution in his new book The British Are Coming. Here's an interview with the author over at NPR. I've read the first two in the Liberation Trilogy (the third is on my short to-do list), and there is every reason to believe that this new book will measure up to the same high standard.
