[TowerTalk] Questions

[K7LXC at aol.com]

In a message dated 7/3/2007 7:19:37 A.M. Pacific Daylight Time,  
k0rwl at townsqr.com writes:

>  The base will be a BPC25G  with pier pin atop 4x4x4 concrete.  
 
    I'm not a fan  of pier pin bases because of the extra work involved 
temporarily guying the  first couple of sections. While they're necessary for big 
guyed towers, for a  tower like yours it's totally unnecessary. Sinking the 
bottom of one section  in the concrete is easier all the way around. 
 
>  I will be using 2 sets of  GA25GD's for guying, through three GAR30s with 
equalizer plates.  while  living on 7 acres, the power company has run the 
power line through the middle  of the property thus causing me to have only one 
place for the tower.  I  am setting base and one (east) guy on level ground.  
The guys to the  southwest and northwest are slightly downhill from the base 
requiring 3-5 feet  more cable.  The cables are all 120 degrees apart and the 
prevailing  winds here are from the wsw.  I have a large grove of trees from the 
sw  to the nw on the property away from the tower which may ebb the winds a  
bit.  While I've got engineer drawings on how the base is to be set up, I  
cannot find anything on how to mount the guy anchors.  Is it like the  base with 
4x4x4 concrete, rebar, how is the GAR30 attached?  
 
    Unfortunately  the info isn't on the Rohn online catalog. It's a CB-1 
which is 2'x2'x4' deep.  There is 0.7 yards of concrete in it for the end of the 
anchor rod and the  rest is backfilled. There are just four #6 pieces of rebar 
(3/4") vertical in  the holes.  
 
>  After all of this is done  the plan is to mount a Cushcraft XM240 and 
TH7DXX on the tower.  What is  your recommendation for a mast to handle both 
 
    Depends on your  local windspeed conditions (at _www.championradio.com_ 
(http://www.championradio.com)  under Tech Notes  if you don't know) and the 
spacing of the antennas. Typically you'll need a  steel tube around 65 kpsi 
yield strength; e.g. A520 or SAE 1026. Make some  phone calls to steel tubing 
suppliers and you'll find someone that has it.  

>  and hopefully the T2X will  turn it.  
 
    It's about the  minimum but should be fine. 
 
>  Which antenna should go on  top and approximate spacing?  
 
    I like the  biggest antenna at the bottom since it's usually the one 
that'll need future  maintenance and being at the bottom will make it easier to 
get it up and down  if necessary. An additional 8 or 10 feet of height is just a 
small percentage  of wavelength and doesn't have much effect on the arrival 
and take-off angles.  

I've used  402CD's as close a 6 feet but more is better. Ten feet would be 
FB.  

Cheers & tnx for your kind  comments,
Steve      K7LXC
TOWER TECH -
Professional tower services for  hams
Cell:  206-890-4188



 



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