[TowerTalk] NVIS and Antenna Height

[Jim Brown]

On 1/17/2019 2:59 PM, Keith Dutson wrote:
> I guess I should have said NVIS rather than cloud warmer.   Used a 40 meter
> dipole at 30 feet to work a lot of stations in US from YN2 a couple of years
> ago.

This is another serious misconception caused by the way ARRL plots 
vertical radiation patterns, setting the scale to the angle of maximum 
radiation. If you plot patterns for all antenna heights on the same 
scale, you learn that, in general, higher is better for NVIS, and, over 
"flatland", for DX too.

http://k9yc.com/AntennaPlanning.pdf shows that 0.2 wavelength is 
approximately optimum height for horizontal antennas for NVIS, and that 
height has to be increased a lot to degrade NVIS. It also shows that 
verticals are lousy for NVIS because they have very little radiation at 
high angles.

I STRONGLY agree with KQ2M regarding the importance of terrain, and you 
don't have to be on a mountaintop for it to matter a LOT.

73, Jim K9YC