[600MRG] more antenna musings

[michael polia]

Jim,
I'm designing/building an inverted L for my QTH for 475 KHz. It's a variation of the top-fed Marconi or Steeple antenna described in "Practical Wire Antennas" by John Hayes, G3BDQ. The vertical section is a 25 foot length of 3/4 copper pipe grounded at the bottom. The top connects to a horizontal run of 18 AWG back to my house, about 130 feet.  I'm feeding it via a tuner where the horizontal run enters my house. 
I chose this configuration hoping to get most of the antenna current maximized in the vertical section rather than using a base-loaded vertical w/ coil losses.

I measured the impedance at the feedpoint end of the horizontal section to be roughly 350 ohms w/ -j 400 (more or less) using a Palstar ZM-30. Then I custom designed a tuner to match that to 50 Ohms.
I still need to build out the ground systems; radial, etc. but I do get a decent SWR less than 1.4:1 at 475 KHz.
 Right now I'm still playing, futzing, etc with about 1 watt power level but hope to be up and running with 20 to 30 watts soon.
73 MikeAB1AW