The 160 Meter Inverted L Project
I have a lot of open space around my house with many tall trees nearby. The wife & neighbors are not at all concerned with what I do with antennas.
The thought was that I would take advantage of the existing ground and radial field that I have been using for my 40 Meter Vertical experiments. It is also handy that I have a nice little barn there with electricity. The plan for an L quickly degraded to an end fed ¼ wave wire. As things progressed the wire left the barn at about 45 degrees up and West to about 50 feet. Then it turned North and continued to about 60 feet until the full length of wire was deployed. Prudent trimming left about 120 feet that has a resonant dip at 1.9 mhz. Unfortunately, there was also a high SWR (2.4) associated with the measurements. Measurements were made with an MFJ 269 Analyzer. The actual measurement of the antenna at the terminals was Z = 20 +j8. Calculations performed with TLW (Software Included in recent ARRL Antenna Handbooks) indicated it would take an L-Match with 1.39uh and 4041pf to correct to the 50 ohm Coax.
Not wanting to expend the resources to try that match, I opted to try an on-the-air test using an SGC-237 Autotuner. (The SGC-237 Autotuner automatically matches the antenna to the Coax. Unfortunately, it is limited to 100 watts of power and there is no clue as to the costs in efficiency!)
That test indicated the antenna does indeed work but leaves a lot to be desired. It would appear that the radiation is neither horizontal nor vertical.
It is best that this antenna be dismantled and other solutions be pursued.
Jan 4, 2010
Discussion on the local tech net reminded me that polarization is not all that important to successful operation. Further, in this instance the horizontal section of the antenna is mostly functioning as a capacitive hat.
However, this configuration is directional and the test was conducted in the direction of minimum gain. Further testing & tuning will be performed.