[TowerTalk] Tower and antenna decisions

[Jim Brown]

On 10/26/2013 9:05 PM, Richard Karlquist wrote:
> After considering the above, an outboard tuner looks like a much
> better option.  Or use antennas that are well matched in the first
> place. 

Exactly right.

Two VERY important fundamental facts are that both 1) the behavior of a 
power stage (linearity, efficiency, gain) and 2) the response of filter 
networks, are exquisitely dependent upon source and load impedances. In 
our case, the source is the dynamic (AC) output Z of the rig (usually 
less than 50 ohms) and the load is the antenna as reflected by the 
transmission line.

We MEASURE filter networks using 50 ohm sources and terminations, but 
practical antennas, even with a great tuner, are at best approximations 
of 50 ohm loads at the TX output at the operating frequency, and are 
wildly different at all other frequencies, including the harmonics those 
filters are intended to suppress.To assume that these 50 ohm 
measurements represent the behavior of these rigs and filters with real 
antennas is total fiction.

These facts are no less true today than when I studied EE 50 years ago.

73, Jim K9YC