"Time Traveler" wrote in message
...
Broadcast stations and shortwave are vertically polarized.

AM broadcast band signals are vertically polarized when they're propagating
in ground-wave mode: in other words, over distances up to 150 miles or so.
Once it bounces off the ionosphere, as in late-night skip, the polarization
is random. It doesn't matter which way your antenna is polarized then.

Short wave is almost all ionospheric-skip, so it never matters which way
your antenna is polarized.

It would
behoove you to go vertical as a first choice,horizontal second.From
memory I believe there is a 50 per cent drop if a station is
broadcasting vertical and you are receivng horizontal.

That's the rule-of-thumb, but it only applies to line-of-sight (VHF) or
other space-wave transmission (some ducting, satellite, etc.). There's no
way to predict polarization in sky-wave, which is ionospheric skip. And true
ground wave is always vertical, as one end of the wave is "sunk" into the
ground.

This stuff is covered well in all editions of the ARRL Antenna Book.

--
Ed Huntress