Alfa Radio Ltd. Si Units.

Alfa Radio Ltd.
11211 - 154 Street, Edmonton, AB, T5M 1X8

It is the policy of AlfaRadio Ltd. to use SI (Metric system) in its measurements where possible.
SI is the standard method of units and measurement in all but three counties in the world. See SI standards
Conversion to the old Imperial units is possible see Conversion .

SI Units: SI - - International_System_of_Units

SI Standards: Bureau_International_des_Poids_et_Mesures Home page

ISO: International_Organization_for_Standardization

Torque: Nm An explanation of Torque

kilogram: kg The standard unit of Mass (kg is NOT a unit of weight see Newton) Difference here

Newton: N A derived unit of force.

Wind Load: A poorly defined non-standard value used to express the loading on an antenna due to wind, typically expressed in pounds per square inch or square feet. This often does not take into account: density of air due to humidity, elevation, airborne particles such as sand, water and ice as well as several other factors such as icing on the antenna. It is a poor method of determining the loading on an antenna or rotator due to the non-standard way in which manufacturers rate the antennas and rotators. If there were a standard method of defining the way to measure this value and if all manufactures used this method, then it would be OK.

These links may provide some insite to the problem:

ARRL - QEX K7NV WIMO NRC - Canada W6NL Powerline

Some things to consider when reviewing rotators and /or antennas:

Antenna wind load is fine to determine if your tower and/or mast can survive, or a rotator if it is mounted outside the tower.
Wind load ratings do not address how symmetrical the wind balancing is.
If wind was straight, there would be no horizonal torque (if antenna was wind balanced.) only vertical torque on the mast.
It does not say anything about the momentum the antenna builds up from its' movement in the wind.
Momentum or flywheel effect needs to be taken into account:
The momentum and/or flywheel effect is the shock load that breaks rotators.
You can have several antennas with same windload but they could have vastly different rotational torque profiles when measured at the rotator joint.

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