[TowerTalk] Positive ID of Unknown tower on Trailer

Sun Jan 16 22:49:21 EST 2005

Folks:

I am trying to positively ID the tower mounted on a tower trailer that I 
picked up, and I am refurbishing.  The tower is 3ea 20 ft sections, nested, 
slightly taller than 20 ft, and looks like a Tristao tower, (now US tower) 
from the lattice work.  Lattice work is flat steel diagonals, with heavy, 
open channel horizontal cross members.  The center to center (face) 
dimensions of the corner tubes for each of 3 sections is:  24.5" 20.0", and 
16.5", measured at the base of each section.  Does/did  Tristao attach a 
nameplate to their towers? Where?

I believe the tower is an HDX 555.

The tower has two motors, (tilt up, and telescope)  each with pulleys, 
rubber V belt drives, reduction gearboxes, and lifting cable drums, with 
1/2" lifting cable.
Tnx,
73, DX, de Pat Barthelow   AA6EG
aa6eg at hotmail.com

>From: "Tom Rauch" <w8ji at contesting.com>
>Reply-To: Tom Rauch <w8ji at contesting.com>
>To: <keith at dutson.net>, "'Frank Donovan'" 
><donovanf at erols.com>,<towertalk at contesting.com>
>Subject: Re: [TowerTalk] There's 'ground', and then there's 'ground'
>Date: Sun, 16 Jan 2005 21:25:41 -0500
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>
> > However, it is empirical evidence that I am seeking.  My
>station ground
> > system design is based on what I have found in ARRL and
>other publications
> > such as the technical documents provided by Polyphaser and
>Harger.  I found
> > nothing published that spoke of the adverse effects caused
>by using braided
> > straps.  Your posts are the only source.
>
>Sometimes we can't easily find things that are commonly
>known or understood in engineering circles. Most engineers
>and many hobbyists understand skin effect, and it only takes
>a moment to reason through this.
>
>The problem with any conductor at high frequency is skin
>effect "pushes" current to the outside. When the conductor
>is woven, current either has to flow from inward moving
>strand to a surface stand through pressure contact or suffer
>a path of greatly increased impedance if it follows the
>original strand inside the braid.
>
>The typical clean copper braid with a basically parallel lay
>and minor weave has perhaps four times the resistance per
>unit length of a similar width smooth surfaced conductor. Of
>course it varies with the braid construction and contact
>resistance between strands, but that is generally for better
>braid that is clean with good pressure contact between
>strands.
>
>In HF power amplifiers, I have found a good general rule of
>thumb is this:
>At 30 MHz is the clean braid from RG-8 cable has about the
>same current carrying capacity as #14 or 16 tinned solid
>buss wire.
>
>It's quite common to have braided leads of rather large size
>overheat and fail even at just several amperes at radio
>frequencies.
>
>Many construction standards prohibit braided straps in RF or
>lightning paths unless the connection absolutely must have
>braiding in order to withstand flexing, and then the braid
>is often substantially oversized to make up for its reduced
>current capacity. It's my understanding NASA restricts use
>of braiding, and I can cite many cases where braiding will
>either cause excessive loss or actually fail in high current
>RF systems.
>
>By the way, that permanent loss increase you see in coaxial
>cables that have been wet, even after they dry back out? It
>primarily comes from loss of strand contact in the weave
>caused by the tarnishing of conductors.
>
>If the Handbook tells readers braiding (especially braiding
>that might be exposed to moisture) is a good idea in high
>frequency or lightning grounds....they are giving bad
>advice.
>
>73 Tom
>
>
>_______________________________________________
>
>See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless 
>Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any 
>questions and ask for Sherman, W2FLA.
>
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