Topband: BOG antenna-more info ?

[Guy Olinger, K2AV]

"The ground around here is mostly sandstone, clay, shale and sand. The 
BOG could run about 270' in a straight line but that doesn't seem long 
enough even using a pre-amp."


The issue for the unpredictability of BOG performance is (IMHO) the 
velocity factor when placed on the ground, which depends on some as 
yet poorly defined relationship to ground characteristics.

I have measured VF's on dipoles laying on the ground as low as 60%, 
meaning that an 80 meter dipole laying on that particular ground is 
almost resonant down at 160 meters.

W0UCE has a NW pair and NE pair of phased 270' BOG's (on property 
where a traditional 500' beverage is not workable) which work very 
nicely. The need for a preamp is arguable, depending if you want the S 
meter deflection to drop when you switch RX to BOGs.

Their performance deteriorates in an extended dry season, resulting in 
an activity called "watering the BOGs" which restores their 
performance, sometimes wishing that he "had a bog for his BOGs".

Making the wire "slow" by placing it on the ground means that the 
incoming wave's exciting all points on the wire does not sum the same 
way at the feed point, because the ELECTRICAL distance from each point 
of excitement along the wire to the feed is longer or not 
proportionately, depending on how far out the wire. With bare wires at 
non-garroting heights above ground, this is not an issue.

This issue changes design, including "best" terminating resistance, 
and particularly renders useless for BOGs the traditional lengths for 
elevated beverages.

73, Guy




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