Re: Double dipole better than YAGI 5 elements??


"Jim Lux" <james.p.lux@xxxxxxxxxxxx> wrote in message news:fsh1ts$no8$1@xxxxxxxxxxxxxxxxxxxx
John KD5YI wrote:

"user" <dag@xxxxxxxxxxxx> wrote in message news:fs91dk$r6d$1@xxxxxxxxxxxxxxxxxxxxxxxxxxxx



Take a look here too:
http://cordis.europa.eu/ictresults/index.cfm/section/news/tpl/article/BrowsingType/Features/ID/89327


“The transmit antennas need to be spatially separated by between 10 and 20
wavelengths and a delay applied to one antenna to achieve effective
de-correlation. The amount of separation and delay depends on the type of
environment to be covered,” says Bard.



Can someone explain this de-correlation to me? Is this not the same as a phase shift?

They're talking about that the received signals from the two antennas are decorrelated, generally, with respect to the multipath. For the two direct paths, it is just a time delay difference. But when you throw reflections into the mix, they'll be decorrelated.

Virtually all DTV receivers use some form of adaptive RAKE receiver to effectively utilize the energy in the multipath and to provide resistance to multipath fading. To the receiver, adding another transmitter just looks like another reflected path.



Would there not be a de-correlation when moving from
broadside to end fire?

Depends.. How far did the phase center move when moving from broadside to end fire.


Well, as it says ABOVE, “The transmit antennas need to be spatially
separated by between 10 and 20 wavelengths...", so that must be how far.

.