On 11/1/22 4:36 PM, WB2UAQ wrote:
Jim Allyn, I don't have a tower to test this idea. I read the Notes on measuring tower resonances that you posted where Rudy couples to the tower with a rectangular loop. What if a number of insulated turns are wrapped around the tower (tighter coupling than with a loop standing parallel to the tower) and the impedance looking into the loop is measured? When the tower structure resonates the impedance should show a drop when energy is sucked out of the nanovna. I am thinking this will happen if the tower is grounded or not. Wish I had a structure to test this on. \
I don't know that you want to wrap the coils *around* the tower. You want them magnetically coupled - which is sort of challenging, since you'd normally have a magnetic core, the tower is "one turn", and your test coil is multiple turns.
If you have a rectangular loop next to the tower, but "sticking out", the field from the closer wire couples more than the field from the farther wire, so you get some coupling (as an "air core transformer") much like some magnetic loop antennas do.
I would think, too, that you could capacitively couple
