[TowerTalk] Half Wave Verticals @ WWV/VH

[Jim Reid]

It was wondered:

> Are the antennas phased?  

Yes.  These are the 15 MHz antenna array. Two half-wave 
vertical dipoles separated by a quarter-wave length and 
driven 90 degrees out of phase

>Or are they antennas for two different freqs?

Nope,  phased on 15 MHz.

> They look the same heighth.  There's no mention of  
> coverage preferences in the text; just 'omnidirectional.

They are phased to provide a "cardioid" pattern to the
West.  So to the East,  the signal is way down.
 
> I'm thinking seriously now of elevating my ground mounted 
> vertical to at least 1/4-wave of 20m -- if it's good enough 
> for WWV, it's good enough for me.

Excellent idea,  but,  you must provide an excellent ground
radial field to get ALL the benefit!  And,  it is also 
a good idea to provide the "other half" of the antenna with
a steeply sloping set of elevated radials,  just as at WWVH.
 
> Can two antennas be fed for an omni-directional pattern?  

No, there is nothing to be gained from two vertical antennas
for omni coverage.

> Why two and not just one?  

Phased cardioid pattern to the West.  Over to Asia,  JA, DU
land,  etc.

The goal was US Naval facilities/ships located in the far Western
Pacific,  so the cardioid pattern faces West.  Now,  of course, the
ships of the fleet are all using GPS,  so the NIST and WWV/WWVH
are searching for reasons to continue "to be".

There is much technical info on the previous link provided,  but
you must click about to find same,  hi.  Including,  some excellent
photos of the transmitters and 10kW power supplies out here
at WWVH.

73,  Jim KH7M



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