How are the broadcast signals are polarized?

Most U.S. FM broadcast stations broadcast their signals now with some form of a circularly polarized antenna  .   It's actually very rare to find horizontal only or vertical only stations except in odd situations or if we need to lash up an emergency antenna for some reason or other.   There are a few horizontal only stations using a log periodic transmit antenna, but they tend to be rural low power translators.  In our case our transmit antennae are circular. 

You may be interested in seeing the typical brand & models that we use here:  https://eriinc.com/product/rototiller-circularly-polarized-fm-antenna/

You may find this website useful for finding a direction to aim your receiver antenna here.  https://radio-locator.com/

 As an alternative to a Yagi, we are fond of this antenna   https://www.dxengineering.com/parts/dxe-afhd-4?seid=dxese1&gclid=Cj0KCQjw9MCnBhCYARIsAB1WQVW4d_IWY4by4OqoDMepp0foW0hLAdpk5jJhjrX8gJXdSWBnvnrbR90aAgr-EALw_wcB

We've also had success with this half wave antenna:  https://www.amazon.com/MAGNUM-DYNALAB-ST-2-FM-Antenna/dp/B003ETW2F0