[TowerTalk] [Bulk] Re: antenna choices

[Jim Thomson]

Date: Fri, 10 Apr 2015 08:56:06 -0700
From: Jim Brown <jim at audiosystemsgroup.com>
To: towertalk at contesting.com
Subject: Re: [TowerTalk] [Bulk] Re: antenna choices

Want to reduce the cost of an antenna? No problem. Pull out the ARRL 
Antenna Book, pick a design, order the hardware, and build it. Or get 
some version of NEC and design it yourself.

While you're at it, keep track of the number of hours you spend. From 
the cost of those overpriced antennas, subtract what you paid for 
materials, and divide that number by the number of hours. Chances are it 
will be less than what you could make flipping burgers at McDonalds.

73, Jim K9YC

##  Nonsense. Tubing is dirt cheap at dx eng and other outlets. 
Any small drill press  will easily drill all the required rivet holes, and fast.
I can flip the table on my drill press over 180 degs... and then it exposes the
V notch trough.....made to hold tubing and pipe.  Only a small V notch is required,and
will hold any size tubing  from tiny stuff up to 4-5 inchs in diam. 

## I have yet to see any ant maker that know how to build a 
proper boom to mast assy, they all screw it up imo.   By the time you get through
fixing the megabuck wonderbar, you may as well call it HB.

##  The .120 inch wall thickness on the boom material that dx eng sells
is superb. (6061-T8).   It slides together real easy. Then just bolt it
with a pair of 1/4-20  SS bolts + nylocks.  Then its easy to configure
any boom you want.   For heavy duty applications, a pair of 6 ft long
3 inch OD x .120 wall  sections are spliced in the middle with an internal 
2.75 inch OD  x .120 wall piece.  Then the middle 6 ft is .240 wall. 

##  Outboard sections continue on with 2.75 inch OD  x .120 wall, then
down to 2.5 inch OD x .120 wall.   Ok,  now your boom is  35 ft long.
Want it longer ?   Continue on with 2.25 inch OD x .120 wall. 
Now you are at   46.5 ft.   For that length, install a truss half way out
each side, and a 2nd truss out towards the very ends of the boom. 

##  The mech software is fun to use to design both ele and booms to any spec
you want.   My 15m boom starts off with 2 inch OD x .125 wall material, then
drops down to 2 inch OD  x .058 wall.  There is 100 ways to fabricate a boom.
This is NOT rocket science here folks. 

##  In N6BTs  book, array of light, he publishes every design you can think of.
YO-7.3  will tweak up any Telrex yagi.  The eles are fixed, so only the tips are tweaked.
I did this for a few telrex 20m yagis..and it make a big improvement.  

##  I just downloaded  the manual for the steppir  DB-36. The boom to ele plates
they use, use additional plates at an angle from below. to support the main plate.
Fubar design.   They could have easily just used a thicker plate to begin with, or
better yet, used channel aluminum.  Typ channel aluminum is the bomb, imo, for
this application. Typ 4 inch wide channel aluminum  has .25 inch thick sidewalls. 
The 4 inch wide portion is called the web.  The web is available in 2 thickness. 
.181  and also .281 inch thick.   Channel aluminum wont bend under a load. 
Comes in 2-3-4-5-6 inch wide widths. Cut it to any length you desire. Local
metal shop just lops off what I require. 

##  baffles me why steppir wants $200.00 just for a pair of 6m directors ! 
I mean, come on, a 6M dir is aprx  9 ft long.   $200 for  2 x 9 ft tiny eles ?? wtf. 
A 3 ft piece of 6063-T832  from dx engineering is $1.48 !   That’s for a .375 OD x
.058 wall.  Heck, F-12 only used .035 wall  for their .375 OD tip sections.   Those 6m 
dirs are worth dick. 

##  My time is my own, so could care less how long it takes to do it right.  Take the cost
of the megabuck ants, then add your time spent re-engineering them, buying the material to
fix em, etc, and  you are into it for a bunch. 

##  and no, they don’t come fully assembled, they come in a  million pieces, in kit form.
So you have to build it anyway.  If u are in a real rush to install rivets..fast, and have an air compressor
in the shop, just get the attachment that goes on the end of the air hose...made by POP and others. 
Then you can blast in rivets  super quick like.   Local metal shop has miles of AL  tubing and also plate
and ditto with channel.   I phone em up and tell em what sizes I want plate and channel cut to. Bam, done,
and I pick it up an hr later. 

##  Take the time you spent reading thousands of tower talk postings, and  you could have built a lot of
ants.

Jim  VE7RF