Retuning the 160 meter OCF

Redoing our 160 meter OCF antenna. Our group changing the length at the northeast side.

Redoing our 160 meter OCF antenna. Here our group took down the northeast side of the antenna, and soldered a different length extension.

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.

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Temporarily removing the southwest end of the 160 meter OCF antenna from the fence post.

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Michael KG4OZK, Emily KM4LLT, Rob KB5EZ, and Matt KA0S. Rob attached an extension to the southwest half of the OCF antenna.

Emily and Rob soldering an extension to the southwest half of the OCF antenna.

Emily and Rob soldering an extension to the southwest half of the OCF antenna.

View along the OCF antenna from the southwest to northeast.

View along the OCF antenna from the southwest to northeast.

Dave KK4IKR reattaching the southwest end of the OCF.

Dave KK4IKR reattaching the southwest end of the OCF.

Matt KA0S tested the 160 meter OCF with his antenna analyzer. He also checked the other dipole antennas that have replaced the OCF on the other bands, to make sure we have the capability on those other bands.

Matt KA0S tested the 160 meter OCF with his antenna analyzer. He also checked the other dipole antennas that have replaced the OCF on the other bands, to make sure we have the capability on those other bands.

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.

After working on the OCF antenna, we reviewed how to use our radio and software for meteor scatter.

After working on the OCF antenna, we reviewed how to use our radio and software for meteor scatter.

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