[TowerTalk] Radial question

[Jim Brown]

On Sat,2/27/2016 7:49 AM, Vincent Weal wrote:
> I'm installing a 40/80 meter vertical (DX Engineering 8040VA-1) which calls
> for 65 foot radials. However, I recently saw a video of an antenna
> presentation by W3LPL in which Frank suggests 70 foot radials for an 80
> meter antenna. I'll be burying the radials about an inch in the ground.

Several thoughts. First, length of elevated radials IS somewhat 
critical, because length affects current distribution, which in turn 
affects loss. N6LF, who has done what may be the most extensive work on 
this, suggests that elevated radials by a few percent shorter than 
resonant.

Second, if you have a lot of radials on/in the ground, length is far 
less critical, and a good rule of thumb is "more is better" and "longer 
is better."

Third, proximity to earth strongly affects the velocity factor of a 
conductor, and significantly lowers the resonant frequency. This can 
easily be a factor of 0.7 - 0.6 for radials laying on or in the ground. 
Applying this factor, for 80m, radials in the range of 50 ft would be 
close to resonance.

If you want to go to the source on this, google to find N6LF's website 
and prepare yourself for a lot of reading.

73, Jim K9YC