I have a Rohn catalog ca. 1976. At the end of the section on 20G, it has a
picture of 20G and 11G side by side. The tower in question looks like 11G.
For comparison, both are laid out horizontally between two supports with
weights on them. The 20G shows little sag, but the 11G has really, really
Also, a comparison of 20G and 25G specs reveals that the 20G has 18 gauge
tubing, while the 25G has 16 gauge legs. Also, the 20G is rated at about 60
percent of the 25G in terms of maximum loading.
One might want to keep this in mind before putting much of a load on the
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