[Elecraft] Remote Antenna Tuner

[Vic Rosenthal]

Bill Johnson (WR Johnson Consulting) wrote:
 > If the antenna doesn't match transmitter output without  a tuner,
 > does it really matter where  the tuner is placed as long as the rig
 > output is matched?

If the antenna doesn't match the the impedance of the line, there will 
be an SWR greater than 1 to 1 on the line.  Inserting a tuner at any 
point will enable the SWR to be reduced to 1 to 1 on the portion of the 
line between the transmitter and the tuner.  It will have no effect on 
the SWR on the portion of the line from the tuner to the antenna.

 From the point of view of the rig, there is no difference -- as you 
point out.

Every kind of transmission line has a certain amount of loss which is 
proportional to the length of the line.  Coax has higher losses than 
air-insulated balanced line.  Under conditions of low SWR this loss is 
usually negligible for HF amateur installations.  However, high SWR 
multiplies the losses that would be incurred by a matched line.  Usually 
the line is short enough and the SWR low enough that the loss is STILL 
negligible, so it doesn't matter where you put the tuner.

But when you get SWR in the range of 20-50 to 1, such as you would get 
from feeding a dipole on its second harmonic or loading a short whip, 
losses DO become significant.  The example I gave before of a 40-meter 
dipole operated on 20 meters, fed with 50 feet of RG-58 and wasting 90% 
of the transmitter power is instructive.  In that case, it would be 
highly advantageous to put the tuner at the antenna feedpoint.

Vic K2VCO