[TowerTalk] High VSWR

[Jim Thomson]

From: "dj7ww at t-online.de" <dj7ww at t-online.de>
To: Jim Thomson <jim.thom at telus.net>
Cc: "towertalk at contesting.com" <towertalk at contesting.com>
Subject: Re: [TowerTalk] High VSWR

<That is a bad idea, the torque force on the rotor under high winds will become much larger.

<73
<Peter

## Nope.  It  will  reduce  torque  down  to  virtually  zero.  In  his  case, it  gets  even  better,  the  LPDA
is  mounted  ABOVE  the  mast, instead of  the  SIDE  of  the  mast.  Tq  will  be  zero. 

##  Two  ways  to  tq  balance a  yagi.    1- mount  at  center  of  boom, and  use a counterweight  at far  end of  boom,  the  light  end. 
2-   mount  boom  at    CG, then  use a sail /  vane  at  far end .....short  end  of  boom.  

## I  have  used  both methods  with  great  success.  Both  designed  with  software  from  DXE  +  also K7NV.  

##  Fellow  across town has a  20m  yagi,  with CG  way  away  from center of  boom.    It  would   rip  up  a  T2X in  mere
months.  After  3  destroyed, I  designed a flat  plate  sail  as a TQ  compensator.    It  was  tested on  the  low  30  ft  high  test  tower.
No  rotor  installed,  just a mast  and a pair  of  bearings.  Owner  climbed the  30  ft  tall  bracketed  tower  during  a windstorm, and  could
point  the  boom  in  any compass  direction....  by hand...and  it  always  stayed  put.   Good  enough,  so  yagi moved  to  top  of  higher  tower.

##  zero  problems  with  rotor ever  since,  that  was  13  yrs  ago.   Zero  issues  since  u  can turn it  by  hand.   Its  tq  balanced.   However, 
since  the  yagi is  mounted to the  side of a 2 inch mast,  and  with  boom  directly  into  wind,   there is a slight  offset  between center  of  2 inch boom,
and  center  of  2 inch  mast,   which  is a 2 inch  offset.....  so  not  quite tq balanced for  that  case.    With  boom  broadside  to  wind,  it  is 100%  tq  balanced. 

##  yagis  and  LPDAs that  are  not tq  balanced is a pet peeve  of  mine.   Simple fix.    Alternative is stupid  amounts of  tq  required....esp on  long booms. 

Jim  VE7RF