DB here is my wires description for your green model "6ft-m-nr" with a mast attached and no radials, mounted @ 6' feet above Earth.
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Here is the pattern I get.
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Here is what I get for the pattern if I isolate the mast using Average Earth.
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And, here is the pattern I get if I isolate the mast over Extremely Poor Earth instead of Average Earth.
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My model now is very similar to what you get for your model "6ft-m-nr" with a little bit less gain at 2.96 dbi vs. your gain of 3.22 dbi for the green model.
Here is my wires description for my model with the mast isolated not connected.
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You did a lot of work here and a lot of little details. I had trouble just trying to duplicate what you've done for us. I hope there is an easy explanation. I've only done the first model in green, and I sure would hate to go back and recheck all these models again, which I've already done on my end...just to get my one model at the various heights to 36' feet. I hope I'm wrong and I messed up somewhere here. That is why I posted my wires descriptions for you to check maybe.
Note the only difference between the two wires descriptions is in (Wire 2 End 2) for the 6' vs 5.5' mast where I isolated the antenna.
I think this is a very important topic for us to try and understand a bit more. Thanks!