Quote
jmaryt

,i was always curious about fisher'd stated
"fourier domain analysis"..i believe,but am not sure that this pertains to the 5khz,
and 15 khz frequencies transmitting simultaneously.

j.t.

Transmitting more than one frequency at the same time is technically based on
"Fourier domain analysis" actually. More precise on fact, that some shape of signals
(par example square wave, triangle wave etc.), that are not pure sine wave, are in fact
composited from broad spectrum of sine waves or spectrum of different harmonic
frequencies, that are all sine waves.

So if we need to drive coil with two simultaneously acting sine frequencies (here 5 and 15kHz)
we need to drive coil with 5 kHz square wave frequency that incorporate both 5 and 15 kHz
sine harmonics.

Then we need on RX side two RX channels (for 5 and for 15 kHz), adequate filtering depending
on detector search intention ... etc.

Despite almost equal scheme, CZ 3d detector is not the same as others from Fisher CZ series.

It is different in some filtering stages and dedicated to old ancient coin searching. In conclusion
it is more suitable to old (Roman, medieval etc.) Europe sites, than North America sites, where
mostly new era coins are found. For N. America sites suit better others CZ models, than CZ-3d.

More clarification on how to "frequencies transmitting simultaneously" in drawings below: