Nov 1, 2009

The MPV project II

The MPV rises to 16mtrs !

I have found a top section of an old 12m spiderpole. This came from a damaged Heavy Duty version and has served as an 160m vertical during a HB0 dx-pedition. However, despite wall thickness up to 2mm it didn't last long in high winds.

The 12m fibreglass pole can be spotted on top of a 20m alum mast which serves domestic logistics.

I allocated the top sections in the back of my shed and found them in good shape. A total length of 6.40m is available and it fits tight on the top section (22mm dia/2.5mm wall) of the earlier installed 10m DJ6NI mast. For the experiment I added a couple of hundred windings using 0.85mm lacquered copper clad steel wire from

Nice job done, but a quick check with my antenna analyser using some ground radials and a 3m ground rod, shows resonance at 1570KHz. And I haven't even hoisted up the bottom 10m sections. A few too many windings I say!
With the 40cm overlap and true snug fit the Most Pitiful Vertical is now at 16m.

I run upstairs in order to make a nice 'total view picture' from the 1st floor.
Looking outside I quickly recognize the downside of this kind of structures; wind.
Even the slightest afternoon breeze bends it like this:

Another guying point at the 10m point, just below the black top section, is not feasible. My guying locations are way too close and there's no room for attachment points farther away. Let alone the risk of tangled up guying wire during the daily job of sliding the whole structure in and out. BUMMER.

OK, where are we now?
  • This current 16m version is not an option.
  • Guess that a max of 12m vertical is possible, provided I use a thin wall fishing pole and no extra windings on the top section to minimize the load.
  • Explore option of a T-version, where the top-hat functions as guying. Max 12-14m height?
  • Better install an electrical 30m Bigh Bertha, which needs no guying and is 3m high (and the same amount buried in the ground with several tons of concrete, right?).
What went well?
  • Back yard has been cleaned up
  • Found that chicken mesh-wire functioning as ground screen is a realistic option

Only few weeks till CQ-WW CW

1 comment:

Mark, PA5MW said...

Further field tests have shown serious issues in wind load as well as negative input from the neighborhood.
Unfortunately I have had to put this project to an early end.
Mark, PA5MW