I strive to explain pickups in an objective way that uses measurements and experiments that can be repeated time and time again. Here are a few of my findings. More explanations to come as I find time to post them.
Using an AlphaLab gaussmeter, a tool that measures the strength of magnets, I have recorded magnets both new and vintage.
Alnico 5 -- 1300 mG
Alnico 2 -- 1100 mG
Alnico 3 -- 700 mG
1951 Alnico 3 -- 630 mG
1954 Alnico 5 -- 1100 mG
1957 Alnico 5 -- 1150 mG
I stock and use 38-46 AWG in my pickups. The bigger the number the smaller the diameter. This wire ranges from .0040" down to .0016". Generally most vintage pickups are wound with 42 or 43 AWG. The thinner the wire the more resistance which does not always equate to more output. More on this later.
Inductance is the measurement of the resistance to AC. It must be measured at a specific frequency. We measure this at 120 Hz in series using an Extech LCR meter. These readings are a better way to describe a pickups sound than simple resistance to DC. Resistance to DC will only measure the amount of wire and what gauge of wire is used in a pickup, the more windings and/or the thinner the wire, the higher the resistance. Inductance will take into consideration the materials being used as well as the wire. For instance, if you measure two pickups one with Alnico 5 and the other with Alnico 2, the Alnico 2 will have a higher inductance reading because of the weaker magnet. This is only true if all other specs are equal.
We use a Syscomp digital occiloscope to measure pickups to determine the resonant (or peak) frequency. We measure them without a load. This means that we do not take into consideration the added capacitance of the wiring harness or cable. I do this for the sake of consistency, there are too many variables that occur after the pickup leaves the shop. The resonant frequency of most guitar pickups fall between 3,000-9,000 Hz.