38 Miles NVIS?

[WA2WMR]

I just called CQ on 80 meters with 90 watts. Then I looked myself up on Reverse Beacon and the closest station was 38 miles away with a 10db signal to noise ration. Does this sound like NVIS  or would it be ground wave?

 

[K3MRI]

At 38 miles, round (aka surface) wave.

Here is a nice graph from VU2NSB (https://vu2nsb.com). With 100W, you would have a ground wave propagation at S9 at 100 Km, so 60 miles. Could it be a combination of NVIS and surface wave? Absolutely but you'll never know until you speak to someone. When we do the Cherry Tree net, the reason our signals are fairly subject to conditions, including weather, is that we are mostly using ground waves close by. To get true hyper-local NVIS you would need a near 90-degree takeoff angle on your antenna, which is rarely the case. Our NVIS signal, again depending on the antenna, only really kicks in well beyond the horizon.

Does my argument make sense?

[WA2WMR]

Makes sense. Wasn't aware that 100 w ground wave would do so well. But then, why was Frank AA4ZS (SK) the only one on the Cherry Tree net that I could hear. But then again, I could hear almost everyone on the Friday night 10 meter net. Hmmm.

 

[K3MRI]

Antenna, antenna, antenna. Half the people we spoke with in those days had lousy antennas with steep take-off angles that flew over you. The trick to surface waves is a very very low take-off angle, as in under 10º and NVIS is ideally 80º to 90º. Anything in between is headed for Namibia.