One rule of thumb for the distance considered to be in the "far field" is
roughly 10 times the height of the vertical, or the spacing of verticals in
an array. At this distance, there is essentially no difference in the
distance to the top and bottom of the antenna.
Your friend's house 1 mile away might provide the most repeatable test site,
since a test antenna can be fixed in place.
> Following on from the antenna modelling I did a with EZNEC a few
> months back I am now building the antenna and planning the ground
> system. I want to do some measurements of the antenna (approx 48ft
> vertical) with different ground system components. I can measure the
> differences in feed impedance easily enough (I use Larry N8LP's
> LP-100 vector RF wattmeter). In addition I want to measure the field
> strength with the different ground system components as well. (also
> using the LP-100). My question is how far away from the antenna
> should I measure the field strength? I am primarily interested in
> 160/80/40m Two options spring to mind...
> 1) A friend just over 1 mile away
> 2) I could set up in the back of my car about 400yrds away.
> Any thoughts or advice would be appreciated.
> Dave G3UEG
Antennaware mailing list