1,000,000 Point Coax Connector

The weather broke for long enough for lowering the XM240 40 meter yagi from my Trylon tower. I previously noted that I lost the antenna during the CQ WW CW contest, probably due to a loose connection at or inside the balun. It has happened once before. Losing this antenna cost me a lot in the contest since I had no backup 40 meter antenna due to ongoing antenna work.

The first day I rigged a winch on the ground to handle the lowering and lifting of the 75 lb antenna. My lawn tractor could not be used because its weight is too low for traction on snow. On the second day I climbed the tower with the cable and other ropes to rig the antenna. Before doing that I disconnected the coax at the rotation loop.

It's a good thing I did that first. I had a good look at the connection once I had the weatherproofing removed. At that point I could have dropped the cable and rope to the ground since I knew I wouldn't need any of it.

The problem was the connector. In a way that was fortunate since I really didn't want to lower and lift this yagi in the cold and snow, not to mention the difficulty of getting friends out in this weather and their increasing family commitments due to the approaching holidays. It's a busy time of year.

The UHF female barrel connector is old and not the best quality. Notice that the outer edge has only 4 indentations; the best have a continuous set of indentations. There are typically 2 or 4 matching tangs on the male PL259. When engaged they resist the connection from unscrewing from twisting and vibration. Failure to engage those tangs promises future problems, perhaps sooner than you think.

On one side you can see the orange discolouration and grime from past water damage. The dielectric should be white. Despite the appearance this is the side that is working properly. We have to turn it over to discover the proximate cause of the problem.

At first glance it looks good. A closer inspection reveals discolouration surrounding the centre conductor. By eye (obscured by the camera exposure) it is clearly visible. The same discolouration is on the centre pin of the mating PL259 from the rotation loop. It comes from vapourization of the metal plating.

Sliding the two connectors together and apart a few times tells the tale. There is almost no contact between them. The springiness of the female receptacle tabs is gone. This leaves a gap and hence the intermittent continuity, and arcing when running high power.

The barrel connector is old. How old I don't know, possibly decades. I pulled it out of a bin of new and used barrel connectors I keep handy I ought to have tested it before putting it to use. It is the same barrel connector that was on the yagi when it was atop the big tower, where it also was occasionally intermittent.

With the weatherproofing on the feed point side in good condition I never inspected it as I moved the antenna from tower to tower. The intermittency followed. Each time I managed to convinced myself that other known problems such as dirty relays were responsible. Assumptions are dangerous weapons.

I picked a new (and better quality) barrel connector from the bin, tested it and installed it between the rotation loop and the coax running along the boom to the balun. Done? No, not yet. Troubles never travel alone. They enjoy company.

After testing the new barrel connector -- it was good -- I proceeded to inspect the connector on the rotation loop. It was not good. In addition to water damage there was evidence of arcing. Worse yet the body of the connector rotated. Pulling back the outer shell I saw that there was more corrosion inside the PL259 solder holes and the solder had no hold on the coax shield.

Now thoroughly irritated with myself and the chill from working on the tower in cold weather I removed the rotation loop and descended. In my workshop I pulled it apart and quickly realized I had to discard the coax and connectors. I made a replacement with better connectors and, after testing it, ascended the tower. Although it was a chilly 0 C with snow flurries it was would the best weather for close to a week. So I kept at it hoping to get it done before sunset.

After successfully testing the rejoined sections of coax with an analyzer I did a careful job of weatherproofing with my best materials, then routed and secured the new rotation loop. I descended and cleaned the site in the deepening dusk.

With some trepidation I entered the shack and moved the rig and antenna switch to 40 meters. This time the antenna worked perfectly. Assuming I did it right this time the repair should last. An hour later I made my first QSO with 4U1UN for a new one, counting from when I returned to the hobby in 2013.

I call it my 1,000,000 point coax connector (connectors actually) because that it cost me at least that much in the recent CQ WW contest. My claimed score is ~3.5M. Had I done comparably well on 40 meters the estimated additional 700 contacts and 40 multipliers would have lifted my score to about 4.8M.

According to the raw scores that would have moved me from position #55 to #37 in the single op unassisted high power category. That's a big jump though still not a great score. The higher score certainly wouldn't win me a plaque, not even for Canada. It's annoying though not a disaster. I had no illusions about winning or placing high in the standings.

In a big station there are so many parts that some mistakes and unexpected faults are inevitable. When the mistake is up in the air at the end of a long boom it can be costly. An expedient decision at a critical moment is all that it takes. It isn't easy to force yourself to slow down and test every little thing yet it saves time and pain in the long run.

I'll try to do better. We all should.