[TowerTalk] Cable loss revisted.

[jimlux]

Jim Thomson wrote:
>   I visited some contest stations, and after having a look at things,  cringe at the thought of the loss on the coax cables used. 
> Some had really long runs of coax from station to base of tower.. then more up the tower, etc.  300-400'  was typ. 
> Biggest cables used were 1/2" heliax.     A lot of it was 213-U    Some was LMR-400 or eq. 
> 
> I don't see why one would want to try and squeak out another .5 db  of gain on a longer boom yagi,
> [ then repeat on every other yagi].. then turn around and lose a whole bunch  from the long run's
> of coax being used !!   Sure... 1db  doesn't  sound like much.. but  that's 21% of ur power gone.... and it
> drives me nuts to think I burned up 21% of the power coming out of the  linear.   That equates to 472 watts
> burned up.  [ 2250w pep out  x .21 = 472 w] 

Ham contest stations aren't the only folks who do this.  They do the 
same thing on spacecraft link budgets.. obsess about another tenth of a 
dB in coding gain to get ever closer to the Shannon limit, or agonize 
about tenths of a dB in power amp end-of-life output power, and then put 
the Xband antenna at the end of 6 ft of coax which has 3 dB of loss.