Monday, April 13, 2009

Setting up HF

My station's HF capability is in the making, but rather requires that I set up a decent antenna before I can get operating. Everything about HF is "in the large" when compared to the basic requirements for getting going on VHF - for which my VX-8R is already serving well for the simple task of getting into repeaters and digipeaters.

In the UK I had a 6m/2m/70cm vertical which was compact enough to be securely installed with two stand-off brackets anchored into the brick (yeah, I used to have a house made of brick like most in the UK - these days it's made of dead trees).

No such simplicity is going to work now - both due to the sheer size of the HF vertical I'm planning to erect, and the structural integrity of the building material. Rather, a light-weight tower will be installed up the 3 storeys to the roof apex, with a bracket at the eaves. While this isn't a large tower installation in the grand scheme of things, it will be the largest antenna installation I've made, and hoisting it will be a challenge requiring a bit of forward planning as well as a lot of care and attention while handling a length of metal (including antenna) circa 17m in total length!

The first order of the day will be to build something of a footing for the tower base to rest on. This will also need to include some anchoring rods through the cement/concrete of the footing that will anchor the tower base. Once this is set, the tower can be assembled with the antenna attached and carefully hoisted into place with the help of a few extra pairs of hands.

The plan for stage 1 - the setting of the base is as follows:

  1. Prepare work area
  2. Raise ladder to roof apex and install a pair of strong rings under the eaves near the apex.
  3. Install a small ring/hook on the centreline near the apex and run a plumbline down to just above ground level.
  4. Plan a footing relative to the plumbline (bearing in mind stand-off/clearance at the eaves/roof apex for the upper part of the tower)
  5. Dig a sufficiently large footing trench, and place bars through the trench, including the vertical threaded ones that should present themselves through the top of the tower base plate, and in the correct triangular configuration. The tower should present one edge of the triangle section parallel to the wall.
  6. Mix sufficient cement and fill trench.
  7. Ensure level and correct positioning of bars. Recheck as cement hardens.
  8. Once cement is hardened, install base plate and secure with bolts on threaded bars.

Getting past this to stage 2 will be definite progress!

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