Am Sonntag, 7. Februar 2016 19:14:14 UTC+1 schrieb Jim Wilkins:

The two local station I use that antenna for are near 200 MHz, and I
haven't found loss tangent data on thoroughly dried wood above 50 MHz.
Immersing wood in 280F molten wax certainly forces a lot of water out
the end grain, and seals the wood to keep it out. I made a waxed
pulley from scrap casket mahogany that lasted unchanged outdoors for
many years until a glue joint failed.

I salvaged some mahogany from transmission line switchgear which was dismantled in 2010. There was a date on the gear: 1959. The mahogany was externally weathered, but not at all rotten. The weather resistance of mahogany is remarkable.