In a message dated 98-10-18 23:41:43 EDT, n4gn@iglou.com writes:
> 1) The Rohn book for 90 ft of 45G says guys at 39 and 85 ft for 110 mph.
> But my total ht to the flat top will be abt 87 ft. Having the top guy
> point only two ft below the top sounds awkward to me. Won't that kinda be
> in the way when I'm working on the C4XL? Would I be better off moving it
> down to 82 ft, or maybe just attach right to the top plate? (Can you tell
> I have very little experience working on towers?!)
The reason that the Rohn specs have the guys five feet or so down the
tower is because that would be the preferred configuration for a COMMERCIAL
installation where you have mounts, antennas, dishes, etc. that need to clear
the guys. For ham installations, the flat-top guy attachments are fine if not
preferred.
The only downside to the top attached guys is that it makes it a little
more awkward when tramming antennas. I sometimes disconnect 2 of the guys to
make tramming easier. Use of the recently discussed tiller will be helpful.
>
> 2) I was just about to start driving copper ground rods when someone told
> me I need to use galvanized rods instead for the tower. Engineering
> school is just a vague memory these days, but I can see how this makes
> sense. I'm leaning toward the 9-rod installation (3 per leg), but my
> question is, what should I use to connect the rods, assuming copper is
> verboten?
Ground rod material is determined by the ph of your soil. Unfortunately I
don't recall off-hand which is which.
You'll be using copper wire to attach the tower legs and ground rods.
Polyphaser makes a neat hose clamp with a stainless steel patch so that you
won't have copper on galvanized steel. For ground rod connections, you'll need
a good compression clamp or exothermic joint like CadWeld.
>
> 3) I have a 10-ft mast which is sufficient for just the C4XL. But I'd
> eventually like to have a nice 20-ft mast for flexibility in adding more
> antennas later. I think I can get what I need through a friend who runs a
> local metal shop. The only problem is it will probably not arrive until
> after SS CW. I think it would be much easier to build the tower around a
> 20-ft mast and pull it up through the middle than it would be to install
> it after the tower is up. So do I just wait until I have the 20-ft mast
> in hand before erecting the tower, or is there some trick to installing it
> after the fact (say, next spring)?
>
With a small mast (like your 10-footer), just use a ginpole. The
20-footer can be installed with the Rohn ginpole also but there is a larger
pucker factor. Go with what you've got now and re-do it later. You don't have
to lower the antenna - just hang it off the side of the tower while you make
the mast swap.
Congratulations on your spiffy new tower and antenna system. Three weeks
doesn't leave you much time to do everything! And there's LOTS to do.
Cheers, Steve K7LXC
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