On Wed, 14 Nov 2007 08:51:10 -0800, Jim Lux wrote:
Roy Lewallen wrote:
I'm glad my harping on this topic (mostly via Chapter 8 in the _ARRL
Antenna Book_) is having an effect, and that some folks are catching on.

The receiving antenna trick is to begin with elements that are either
very short or very lossy or both. This reduces the effect of mutual
coupling to a negligible value, so all elements will have the same
source impedance. Then the transmission lines are all terminated in
their characteristic impedances at the receiver end. This is the
condition under which the delay in the lines equals their electrical
lengths. Under those conditions, the scheme works nicely.

Or, as the OP mentioned, if you have an *active* array, with buffer
amplifiers at the elements, the amplifier provides the needed impedance
characteristics.

If you're speaking of phasing together two or more *active* antennas,
you'd best employ identical brand and models of the devices. Elsewise,
knowing the phase change _through_ the active antennas would be a crap
shoot.

Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
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