[Elecraft] ARRL book on receiving antennas

[Fred Jensen]

KFBK's are actually two, phased for day-night directional service.  Been 
awhile since I saw them but the bottom insulators were maybe 10 ft above 
ground level [I'm 6'2" and it was just above my reach] so the feedpoint 
is a tiny bit higher than 1/4 wave.  1/2 wave at 1530 KHz is just over 
300 ft and the feed system at 50 KW is mechanically complex and pretty 
heavy.  I think [not sure where I read it but it was moderately 
recently] that KFBK's Franklin is the last AM broadcast one in NA.

NIST photos of WWV HF antennas show about the same height more or less.  
WWVH uses 2-element phased elements to put a cardioid null at the CONUS 
to reduce interference.  I would think that getting anything [including 
ground] farther out in the near field would reduce losses.  The choice 
is an engineering cost-benefit trade off of course.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 9/10/2018 11:41 AM, Jim Brown wrote:
> On 9/9/2018 7:02 PM, Wes Stewart wrote:
>> The WWV antennas are center-fed vertical dipoles. 
>
> Thanks for the reminder about this -- I vaguely remember reading about 
> their antennas years ago.  Question -- from the description, is the 
> feedpoint higher than a quarter wave above ground?  A few years ago, I 
> did an NEC modeling study of HF verticals that showed that doing that 
> improved the vertical pattern and seemed to suggest that it reduced 
> ground losses. Your thoughts?
>
> The study is here.  http://k9yc.com/VerticalHeight.pdf
>
> 73, Jim K9YC
>
>
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