No, the absence of a specified vertical power in the construction permit does not prohibit the use of vertical or circular polarized antennas by an LPFM station. LPFM stations are generally allowed to use either horizontal or circular polarization. When constructing your LPFM station, you have some flexibility in choosing the antenna polarization that best suits your coverage needs.
LPFM stations are allowed to use vertical or circular polarized antennas according to §73.816(a) of the rules. These antennas can be employed without the need for a horizontal antenna. Circularly polarized antennas, including "penetrator" style antennas, are also permissible for LPFM stations.
The choice between horizontal and circular polarization is typically based on engineering considerations, terrain, and other factors that affect signal propagation. Both types of polarization are permissible for LPFM stations, but the station's construction must adhere to the parameters outlined in the construction permit, including the specified horizontal power and the coordinates of the transmitting antenna.
If you plan to use circular polarization, it's essential to ensure that your equipment and antenna system are designed and installed correctly to achieve the desired polarization. Additionally, your station's operation should remain within the power limits and other technical specifications specified in the construction permit.