Topband: E51D and OHQP

[n4is at comcast.net]

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Contrary to what you hear repeated on the bands year after year, what Jim said is *exactly* right! :-)
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I'll add that NVIS is rarely —if ever— useful for working DX on 160m.
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 I am sure we never going to learn 160m propagation, but we can learn the basic stuff. We can learn by example or by engineering it.
I moved outside Sao Paulo back in 1986 (I was PY2DP), first time in an almost rural suburb area. I build a 160m dipole/inverted V with the apex 35 ft hung in one three. With 800 W,  I experienced a pile up of JA's on 160m  , JA is the antipode of SPaulo, the far you can go, few weeks later I run a pile up W4 W2, East Coast US on 160m CW. 
So, by experience, the best antenna is the one you have, and you can use.
By engineering, You can check with any antenna modeling software. Any dipole has actually two different pattern,  one vertical polarized pattern along the wire an another horizontal polarized pattern broadside with the wire. Use 3D to separate the two pattern using EZNEC. One line is green and another is red.
So the dipole or inverted V performs as a vertical antenna along the wire, like any short vertical, but.. and here is the but. A vertical antenna is good for TX, and a horizontal antenna is good for RX, the two pattern are 90 degree apart, together they become a unidirectional antenna. 

Jim is 100% right on both subjects I mentioned above. We just seems not to care about the basic stuff anymore.

73's
JC
N4IS