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.
Conclusion:
It is best that this antenna be dismantled and
other solutions be pursued.
Jan 4, 2010
Project
reconsidered…
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.