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Why do you use any attenuation? You're not so close to any of the towers, so you shouldn't be getting overload from them. And you don't want to attenuate them if they're not overloading your scanner. That may be why you're not getting Mt Ord or Humboldt very well.
Or do you happen to live close by to some other transmitter site that is overloading your scanner, which forces you to use attenuation?
Another thought, do you happen to be in the shadow of a hill/mountain or tall buildings that happens to be in the line-of-sight path between you and Mt Ord and/or Humboldt? That could also block their signals.
When I was up on South Mtn a few months back, I had to use global attenuation to cut down on the overload I was getting from all the tower sites there. But that's an extreme example of actually needing to use attenuation. Unless you're close to a transmitter, you shouldn't need to use it.