I used eight elevated tuned radials. They angled about 45 deg from about 4' at the feed to ~15' for their horizontal run. To initially tune, I used my MFJ-259 to feed a pair of radials (dipole), then cut the rest to match them. I set the system resonance via the length of the vertical/horizontal "L".
Your point is a good one. It may be that all I was doing was tuning the entire antenna system...radials and L portion...by adjusting the length of the L. I never fussed with the length of the radials after build, nor did I check them for tuned length. I have other 80-90' trees available, but now am considering a top loaded wire vert to see if it's more frequency stable as temps change. 73, Gary NL7Y > Hi Gary, > > The frequency shift may have been partly due to the raised radials and > relationship to the freezing earth. > > Frozen earth becomes an insulator so capacitive coupling between unfrozen > earth and radials is getting less as temperatures drop. This can be overcome > somewhat by also having on ground radials connected. This also helps the > transmitted signal. > > Sorry you lost your tree. > > 73 > Bruce-K1FZ > >> >> The following obs were an annual occurrence until my 85'+ support tree blew >> down this year. The 160 antenna described below was supported by the tree, >> and was no more than 4' from the trunk in the middle...the top an bottom >> were closer, ~1'. >> >> A wire Inv-L (#12 stranded THHN) with tuned elevated radials for 160, pruned >> in summer, dropped in resonance with each winter's freezing of the support, >> surrounding trees of similar height, and the ground below. It took up to 3' >> of vertical shortening (~2%) at the feed point to return it to 1.825, versus >> the same resonant point in summer. >> 73, Gary NL7Y _______________________________________________ Stew Perry Topband Distance Challenge coming on December 29th.
