If you are changing nothing except the impedance matching, you can put
the field strength meter anywhere, and the highest reading will mean
you've adjusted it for the strongest signal at any distance.

Roy Lewallen, W7EL

Norbert M. wrote:
When matching a very short whip one gets a big reading but
further down the road is could all be dissapeared.

Can a closeby fieldstrenght measurement be done ?
The magnetic field is also great with a short whip.