[TowerTalk] G5RV vs 40M dipole

[Fuqua, Bill L]

   Not everyone knows that a tuner only protects the rig. That is the job of a dummy load.
In fact the tuner matches the impedance of the antenna system to the rig and not only that,
by doing so providing the antenna with a conjugate match, that is to say the antenna's radiation 
resistance is matched and its reactance is also matched by the equal and opposite reactance thus
making the antenna system resonant. If the antenna has a radiation resistance of 10 Ohms and
a capacitive reactance of 100 Ohms the antenna tuner matches it with 10 Ohms real resistance and
an inductive reactance of 100 Ohms thus providing  maximum energy transfer. While at
the same time it provides 50 Ohms resistive load for the transmitter. 
  Resonating the antenna system with a tuner is equivalent resonating the antenna. The only difference
is that there may be some additional losses within the tuner and transmission line which are generally 
minimal at HF frequencies. Also, there is a reduction in bandwidth of the antenna system. 
  Yes it does change the currents and voltages in the antenna. The G5RV was an antenna developed back
when we had tube transmitters with a PI network output that could accommodate a broad range of 
impedances. It also was made to work on 5 bands.
  Just about every AM broadcast antenna system has an antenna matching network. It is a shame that
they don't work. 
73
Bill wa4lav