in Russian

файл CLASSIC SL3.DSN - в формате Capture OrCAD 7.20.170-S
в схеме могут быть ошибки, но не специально сделанные .
На схеме не показан стабилизатор LM 2930T.
В classic III применена катушка Blue Max 450 (950?)
типа "кольцо" диаметром 24см ,самое интересное на
 ней - номер патента (U.S.Patent #4293816)
Чувствительность classic III на воздухе 
5коп СССР
 в режиме макс.дискриминации(только цветные)     -30см
 в обычном режиме ALL METAL                      -35см ,
 в режиме PINPOINT(Плавное нарастание громкости) -40см 

частота передатчика 6592 Hz. (T=151,7 us)



in English

A file CLASSIC SL3.DSN is Capture's OrCAD 7.20.170-S
format. At the circuit may be mistakes, but it is done
not specially. LM2930T is not figured.
A coil is Blue Max 450 (950?), 24 cm of diameter.
Test sensitiveness on 5 copecks of ex-USSR :-) 

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For a start you can look up White's patent # 4293816 on the US Patent Office web site
This may not exactly match any of the coils they are selling today but it gives you some basic information that would be helpful in building your own.

There is a capacitor across the transmit winding that tunes it to 6592 Hz.

Robert
---

Fisher uses the fundamental and the third harmonic (15kHz) as its two frequencies. TX amplitude was 9.8vpp. The DFX uses 3kHz and 15kHz for its frequencies; waveform has an amplitude of 7.3vpp and a total period of 335us, which is right on the nose for 3kHz. The Explorer claims to use 28 frequencies but I think it really only uses 3. Total period is 620us (1.6kHz) and amplitude is 10vpp.

The oscope photos show roughly a period-and-a-half. The times marked are individual pulse widths, waveforms are fully symmetric. 


