I have just returned to ham radio now that I am retired.
My first project is to get a tribander (10, 15, and 20m) up and on the air
as quickly as possible. I have selected a ROHN 9H50 telescoping mast that
extends to 50’ and has guy mounts at 4 locations up the mast. ROHN
recommends each set of guy wires start at 30’ from the base of the mast. I
have bought a pair of Chicago Grips for tensioning the guys and a LOOS
tension meter for setting the guy wire tension to 10% of its maximum
I thought this would be an easy project (even though I don’t have any
experience in erecting towers). But, it hasn’t turned out to be so easy
when I realized the projected area of the tribander I have chosen is about 4
sq ft of projected area (EPA), but the footnotes for the mast say the
antenna load should not exceed 2 EPA! When I add 1 sq ft for the rotator
and mast to support the antenna, my EPA is over 5 sq ft!
So, my question is: should I abandon this project or can I make changes in
the support of the mast so my tribander can stay up even in the 100mph area
max wind speed estimated for my county?
What I have thought of changing is: 1. Not using the ROHN recommended 18GA
wire as the guy wire but going to ROHN 3/16 EHS, 2. Using the software
called MARC (Antenna & Rotator Calculator) to calculate the required steel
alloy and thickness of the antenna mast, 3. Limiting the antenna mast and
rotator to only 2 ft above the top of the telescoping tower mast, and using
4 guys instead of 3 (for a total of 16 guy wires).
Can I make this mast stand up? What are the weak areas and how can I make
them stronger? Would you direct me to books that discuss tower supports?
Thank you for your help… I really need it.
TowerTalk mailing list