I think everyone that has stacking dreams must go through exactly the same
spreadsheet excercise on guying materials. I know I did. A couple notes on what
I did and learned. Nothing new, just felt like adding to the QRM....
0) Yes, we all have budgets. However, look at the tower as a system and
determine where your overall costs are. N3RR did a great job of this and
presents his thoughts nicely on his web site. Check it out. Guy lines are a
large percentage of the cost, but they are also critical to do correctly. Most
everyone will agree that antennas are the #1 priority for a ham station. The
tower keeps your #1 priority in the air so why skimp on it's construction? If
you are stacking antennas down the tower you've already committed to a large
structure with significant costs. Steel conducts, Philly and Polygon rod do
not. Again, you're spending a good deal of money and time on a complex system
- consider present and future plans and be wary of false economies. As a
complete aside, it helps to have an XYL who says things like: "Just use 55G
because I don't want to hear you whine about how 25G sucks to climb."
1) Forget about using clamps instead of grips. I used clamps on my 45 foot
tower (to save a few pennies) and will never ever use them again. Some things
in life are worth a little more money and preforms are one of them. They are
probably easier for the average dude to install properly which would make them
safer as well. Not to say clamps are not safe if installed properly.
2) 55G rocks, but note that the 100 foot 55g tower cited with two guys at
50/100 feet is built to the 70 mph spec. Take it up to 90mph Rohn spec and you
need three guy lines. We're also talking about stacking antennas down the
tower - those antennas will put twisting moments into the tower in ways that
the Rohn specs don't account for, and that the typical ham probably doesn't
understand (I know I don't). Simply saying two guys is OK and going forward
may not be the best approach. Hank and Kurt can comment more if they like.
Having said that, my largest tower is 105 feet of 55G guyed with Philly 6700i.
Is that overkill? Perhaps, but I got a good deal on the sections, and rather
than trying to save 10% of my costs it was a lot more important to me to build
a robust structure that would be sufficient, safe, and which would meet my
predicted needs for the future.
Take home for me was simple: Towers in the 100 foot and higher range are large
investments meant to last a long time. Consider them as long term investments
where the costs are spread over a long period of time and then make today's
judgements with this in mind.
Happy building and do it safely!
Mark
KI7WX (Station in /4, Operator in /6)
http://pvrcnc.org/station/ki7wx/
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