PVRC Contest Seminar March 19-20, 2005 A Few Words About TOWERS Don Daso K4ZA

TYPES OF TOWERS Most common variety—guyed tower (stacked identical sections) What do the guy wires do? restrain wind forces, translating lateral forces into downward compression angular spacing guy tension also translated downward

TypicalTower Guying Details

Hams often move the top set of guys further down tower—allowing easier access & installation of beams, wires, etc. (especially useful if/when tramming antennas into place)

SELF-SUPPORTING Non-guyed towers, free-standing, but principles are the same! Forces translated on to base, which must hold one side up & down simultaneously Thus, bases are usually much larger

CRANK-UPS Crank-ups constructed of telescoping sections, w/overall height set by pulleys & cable system Primary advantage—able to work “closer” to the ground (sometimes tilted over) Retracted except when in use Disadvantages—high cost (including cost of concrete), dangerous, load limits are less

Wind Zone ratings USA

Structures under 300 ft high built to withstand winds: ZONE A…up to 87 MPH ZONE B…up to 100 MPH ZONE C…up to 112 MPH

ICE—can cause serious problems if not taken into consideration

Okay, now what? Selecting a manufacturer/model is complicated process DX/contester height & angles primary importance Typical ham, cost and/or real estate restrictions (what’s practical?) Being pragmatic is perhaps best choice

ZONING (working with & within the law) Permits? Usually easy to obtain with only small fee Inspectors will ask for plot plan & tower specifications (hazard to community) IF it falls, cannot fall beyond owner’s property boundary (almost every state has this rule)

You must also make it difficult to access Known as “attractive nuisance”

Concrete FACTS & FIGURES (Concrete in Practice)

TOWER BASE Soil—assumption is always for “normal” soil, a mix of clay, loam, sand, small rocks IF any doubts/questions, contact your local county’s agricultural extension office

Typical bases small crankups or free-standing towers

Typical TRYLON base

GUY WIRES (for guys who have to guy) Use only material designed for guying! Attaching—to tower & to anchors

Preformed Guy Grip products Insulators—if using EHS (which is often available free from local CATV as short- ends, anything under 200-ft) Non-conductive guys (Phillystran or Polygon fiberglas rod)

ANCHORS Screw-In Dead-man (buried) earth anchors Elevated guy posts

If you learn nothing else, please remember this…. Nominal Strand Size & Recommended Thimble Size 3/16 5/16 1/4 3/8 5/16 7/16 3/8 1/2 Only heavy duty thimbles recommended

EXAMPLES…the right way to use Crosby clips/safety wires

What about GUY lengths? Rule of Thumb: Guy lengths should NOT be evenly divisible by 16 or 22-feet…

K4JA 160M 4-square

Tools & Gear Needed SAFETY always critical!

A “basic” tower installation (contesting focus) IMHO, guyed towers make most sense! Rohn 25/45 usually readily available Simple & easy to build, inexpensive Capable of supporting 2L-40 & tribander stack & wires

Tower Alternatives? Rooftop tower—Create or Glen Martin (cf. W3DQ) AB-577—military “rocket launcher” portable antenna support (cf. K4VV & PVRC’s FD efforts) Push-up masts—Radio Shack/Lowe’s

Purchasing USED tower? If you feel uncomfortable, ask experienced hams to help you inspect prospective purchase. I’ve only encountered structurally-damaging rust once. Align/assemble sections on ground. Always use NEW hardware (SS makes sense).

Now for something completely different…a more “serious” setup… Near Austin, TX, N5CQ’s 195-ft rotating 55G, tries to cover all the angles with six Force 12 tribanders. Three pair are fed with three "Mini Stack-Match" transformers & a Stack-Match control unit on 20/15/10M, allowing selection of any pair, any two pairs, or all three pairs. Three of the antennas are C3s (at 35/95/125 feet) & three are C4XLs (at 65/125/195 feet). Also on the tower are a WARC-7 beam for 30/17/12 meters at 105 feet, a 2L Force 12 Magnum 280C at 185 feet, & a 160M sloper.

Resources Rohn Commercial Commercial catalog catalog

K1VR’s Antenna Antenna Zoning Zoning ARRL ARRL

Questions?

Shameless self-promotion ! TOWER WORKS Specializing in Rohn guyed towers Antenna repairs/installations Reasonable rates Don Daso 515 Withershinn Drive Charlotte NC home cell

Thanks for your attention!