Ground Wave Propagation... how far?

[mondomusique]

Shortwave broadcast related question...

I've only skimmed the wikipedia entry on radio propagation Radio propagation - Wikipedia, the free encyclopedia but I thought I would turn here for the answer...

How far do ground waves propagate, at an example frequency of say 7000khz, power = 100,000 watts? 50,000 watts?

Reason I ask is I live 100mi/160km from Sackville transmitter site (100,000 watts) and 240mi/380km from Monticello Maine (WBCQ 50,000 watts) and I'm wondering if I'm receiving groundwave or skywave from these transmitter sites.

 

[k9rzz]

I would venture you're getting a mix of ground wave and D layer skip. For example, the Chicago area medium wave stations running 50kw can be heard, weakly, up in northern Michigan all day, and they are some 300+ miles away, and on medium wave at noon, you know that's gotta be ground wave. Up on 7,000khz, the D layer is probably refracting some of that energy back down to earth. If you get on the 40 meter ham band with a mere 100 watts, you can talk 300 miles all day long and that's certainly not ground wave. So, again, my guess is that it's a mix.