For portable operations, we have been using a portable rotatable HF dipole from EmComm-Products (model RADS 9-11/A) since 2008. The antenna provides HF (160m, 80m, 40m, and 20m) and a second VHF/UHF antenna on top of the dipole which is fed by a separate cable enabling concurrent operations of both a HF and VHF/UHF radio on one mast.
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| Activating Hatteras Island, NC |
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| KC2VSR (Field Day at Fort Ord, CA) rotating the dipole by giving the mast a simple twist |
When setting up the antenna for portable operations to teach the radio merit badge in 2018, we discovered that we could no longer tune up when using the 20m elements. SWR was extremely high. The was the first time we had an issue when using the antenna after a decade of use. It was time to give the antenna some attention and bring it back to working order.
Diagnosis
Once back home, we brought out each of the elements and check them individually for continuity using a ohmmeter. To perm this test, we placed one of the ohmmeter probes on one end of an antenna element and the other problem on the other end of the antenna element.
All the elements passed this basic test with the exception of one of the 20m elements. The 20m element had no continuity indicating that the wire had a break somewhere along the fiberglass element.
I visually inspected the element for apparent damage and found none. This suggested that something was amiss with connection between the wire and one or both end connectors.
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| Corrosion on the joint between the antenna wire and antenna connector |
Using an X-acto knife I carefully cut a window in the shrink wrap at the junction between the antenna element wire and the end connector to inspect the connection. This revealed corrosion on the junction. Using the continuity tester, I checked for continuity between the wire and both end connections. This showed continuity at the junction to the far end connector and no continuity to the near connector. Ah ha! We found the issue. The corrosion was likely caused from a decade of operating near saltwater and in the rain.
Repair
A brass wire brush was used to remove the corrosion. The connector was then resoldered to the wire along with a copper wire wrapped all the way around the connector to assure positive contact. The connector was recovered with shrink wrap and relabelled as a 20m element. This was a straightforward and easy repair.
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| Repaired 20m element |
Results
We setup a wilderness radio station to teach the radio merit badge at summer camp with the portable rotatable dipole as one of the antennas.
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| Portable rotatable dipole back on the air at summer camp near Truckee, CA |
We setup the antenna with the 20m elements and it performed flawlessly all week while at summer camp. We made numerous SSB contacts on 20m.
Several people have contacted me asking about buying their own portable rotatable dipole antenna. Sadly, the manufacturer, EmComm-Products, is no longer in business. It has been an outstanding antenna.
Good DX and 73,
NJ2X
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