At our last Work-Play session on August 12th, we tried to retune our 160 meter Off Center Fed (OCF) antenna.
We had been using it as our primary multi-band HF dipole antenna. It worked well on a number of bands: 80, 40, and 30 meters, portions of 17, 15, and 10 meters, and the upper half of the 160 meter band. We could not, however, tune our transceiver on the lower portion of 160 meters, including the CW portion, without using an extra antenna tuner. Now we have dedicated dipole antennas for most of those other bands. And so, led by the Station Operation Committee team, we decided to try to retune the 160 meter OCF, to make it usable on the rest of the 160 meter band.
Our first attempt was to change the lengths of the antenna wire at each end. We removed earlier extensions at the ends and soldered different lengths.
The antenna analyzer results looked good. That is, we had resonance now at a lower frequency on the 160 meter band. However, later testing with our rig showed we still had a high Standing Wave Ratio (SWR) with the rig grounded. Time for more Sherlocking.