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Sun, 10/02/2019 - 08:53 -- andyripley

My HF vertical, veteran of GB6VMR had developed a severe wobble, the insulator on the feed point had failed. It was only a piece of tube with a liner and was riveted together. Over time the rivets had loosened and the tubing had cracked. Drastic repair was needed - there's nothing similar on the market at the moment, and as this was one with a raised radial kit, certainly not at a reasonable price.

A few years old and no longer made, it came from Moonraker, an EVX-4000. Had made a good number of contacts over the years. Previous modifications had included those to stop water getting the traps with self amalgamating tape and neutral cure silicone.

The bits had been sitting around home for some time. Next month it's CQWW, and I usually have a bash at that. Others had noticed the rakish angle it could attain given the right wind direction.

First was to think up a solution, so in conjunction with Neil G6MC (for whom I'm a pair of hands in the antenna department) the idea of replacing the tube piece with a solid Delron rod came up as the best fix. So I ordered a suitable item for Bay Plastics in North Shields, 45mm x 250mm.

I'd already done a fair bit of stripping down, so we had the feed point to finally break down and measure up the tubes.
The Delrin we then machined down so the tubing would be a snug fit and then substituted this for the old one. It's a lot better than the original (but then that is the case of most DCD modifications!).

Our initial tests show it's done the job, it is resonant on the 40, 20, 15 and 10m bands, and barring a few minor adjustments in situ, ready for service. Less than a new antenna, and probably in parts than a few weeks' beer supply for the farm.

When finally home and with a new fixing to the short mast, it was on the air and R2DLS was 57 both ways on 20m, then YO2019EU was landed first shout (at 59+) with RV3YR following quickly on. So it's definitely back on form.

Pictures show the insulator when out of the fittings, with the nice crack, the feed point before we started work, machining in progress and initial tests out on the antenna field.

Andy M0DCD