Improvement of LOS horizon with relatively small elevation change

[n6gn]

John, K6PZB, and I flew my quadcopter in a local park today. I attached a camera and the craft towed a thread having markers every 50' so that we could accurately measure the height.  I think this provides a more visual demonstration of the value added by only slight antenna  elevation increase - such as that from a tower.   This is really a demonstration of the cause of "height gain" that we previously showed in "The Flying Antenna" YouTube video where more than 40 dB of S/N improvement was produced with only 250' increase of antenna height.
I've made a new  Video. and uploaded it to YouTube where you can view it.

At VHF and above, where we are currently doing our WSPR measurements,  antenna height is generally much more important than it is at HF. This is because for most communications at VHF, take off angle (TOA) is nearly zero degrees while at HF the ionosphere is normally used and TOAs are higher. Also, at VHF and up, the incremental attenuation from foliage and other obstructions is likely to be larger than at HF. If you watch the video, pay close attention to where the visible horizon is and what it's composed of. I think this may be helpful in assessing the improvements that are to be had by greater antenna height. Rule-of-thumb and RF propagation models each predict on the order of 6-7 dB improvement for every doubling of height. I think this video may help show why this happens.

Glenn n6gn

[KP4MD]

Thanks for sharing this video.  It certainly gives a visual dimension to the effect of antenna height at the frequencies we are using.

Carol