Thanks Grant.
I'm buying the base/cage from the mfg. I think it's all fastened together.
Hy-Gain calls for 2000 psi/28 days and a max of 7 1/2 gls. of water per sack.
I'll talk to the concrete guy about a stronger mix.
I'll be using a raising fixture and tilt plate for the antenna, so no climbing
required.
Mike NF4L
On Nov 30, 2013, at 8:10 PM, Grant Saviers <grants2@pacbell.net> wrote:
> Contrary to other advice, do ground the tower anchor bolts to the rebar.
> Then you have a great Ufer ground, considering the area of the concrete in
> contact with the earth. The rebar should be tied per code, with sufficient
> overlaps and inside the concrete envelope per code. Depending on your site
> and storm patterns, additional ground rods may be appropriate.
>
> For my two HDX589's we mounted the anchor bolts tightly to the base plate and
> tack welded rebar between the six bolts to make a solid sub frame so that the
> bolts wouldn't move when the concrete was placed and vibrated. That way the
> concrete can be placed and finished without the interference from the base
> plate. This sub frame was wire tied to the main rebar cage. After the
> concrete hardened the base frame was installed and leveled. You can order
> stronger concrete (4000psi or higher) than the UST spec (2500) for a very
> slight up-charge. The limiting factor in concrete for towers is tensile
> strength, not compression, considering the tensile/compressive strength
> ratio. A free standing tower has opposite forces in the legs, 1 or 2 in
> tension and the others in compression when the wind blows hard.
>
> Proper water content and curing is important. You can get a slump test and
> post cure strength report from an independent testing outfit. Code required
> this for my towers and I think it cost about $250 per tower, as they were
> poured on different days.
>
> The 589 is positive pull down, but it doesn't matter vs the HD70 since for
> either design the tower weight is always on a cable, unless down and blocked
> for climbing. Better to avoid that anyway and use a ladder or rent a boom
> lift.
>
> The NF7P coax standoffs work well for me - the loop types not the "holds coax
> off the ground" type.
>
> Grant KZ1W
>
> snip..
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