Xtal Set Society, Inc
Kit Index:

Updated 12-13-09
This page:

  • XS-SC The Standard 365 Capacitor Kit
  • XS-90uH The Standard 90 uH Coil Kit
  • XS-250uH The Standard 250 uH Coil Kit
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  • Oat Box Radio Pack
  • XS-402 Little Wonder Crystal Radio
  • XS-500 Basic Crystal Radio
  • XS-W Crystal Set
  • XS-EAK Ear-Piece Transistor Amp
  • XS-DE Dual Ear
  • XS-TGK Test Generator
  • XS-SDLK Smart Dummary Load - for QRP


  • capacitorThe Standard 365 Capacitor Kit

    This kit is designed to assist you in carrying out crystal set measurements and experimenting with crystal set designs. It features a pre-drilled hard-board chassis, pre-drilled panel, panel dial graphics on paper, a 365 air variable, mounting spacer, nylon isolation shaft, pointer knob, hardware, and manual that includes measurement applications. Assembly time is about 45 minutes. As noted in the picture , unit hand capacitance is minimized by including a nylon shaft extender, made up of 1/2- and 1/4-inch nylon spacers. These are also available for purchase separately.

    panel graphicPanel graphic is shown at left. Approximate capacitance, in pf, is shown every 15 degrees. A large sampling of our XS-365 was measured for minimum capacitance; the spread was from 12 to 14.8 pf. Full capacitance, with the rotor plates fully meshed, exceeds 365 pfs, as you can see, giving the unit a bit more range than expected.

    The Standard 365 Capacitor Kit
    Qty: Price: $25.95


     


    90 uH coilThe Standard 90 uH Coil Kit

    This kit is designed also to assist you with measurements and aid in experimentation. Coil Q is > 200, making it suitable for experimenting in the high portion of the 550-1500 kHz broadcast band. Kit includes pre-drilled chassis, a 100 foot spool of #24 AWG hookup wire, A 3.5 inch diameter pre-drilled ABS form cut to 2.7 inches in length, 10-32 nylon standoffs (screws) hardware for mounting, other hardware, and manual that includes measurement applications.

    The diameter of the coil includes that of the form and the wire (with coating). Given that the wire is 50 mils, including its pvc coating, the coil diameter is 3.55 inches. With close winding (snug), pitch is also 50 mils and coil length is pitch*N-1. The diameter of the coil includes that of the form and the wire (with coating). Given that the wire is 50 mils, including its pvc coating, the coil diameter is 3.55 inches. With close winding (snug), pitch is also 50 mils and coil length is pitch*N-1. Self-capacitance, Co, was calculated and measured with reasonable agreement. Using Medhurst's equation:

    90 uH Coil Specification
    dia 3.55 inches
    length 1.5 inches
    form 2.7 inches
    turns, (N) 30  
    Co 6.6 pf
    fo 6.36 MHz
    Q 248 @ 1 MHz
    wire #24 pvc

    Co = k*D,

    where C is in pf, k is a function of length/diameter of a coil, and D, the diameter, is in inches, our coil has a self-capacitance of

    Co = .45*3.55*2.54 ~= 4 pf.

    The self-resonance of the coil, fo, was calculated knowing its L and Co, indicating a value of 6.36 MHz. Q was measured using the two-frequency method. Details can be found in "Standard Coils and Capacitor, With Uses," in The Xtal Set Society Newsletter, Vol. 17, No. 5, September, 2007.

    The Standard 90 uH Coil Kit
    Qty: Price: $18.95




    250 uH coilThe Standard 250 uH Coil Kit


    This kit is also designed to assist you with measurements and aid in experimentation. Q is > 150, making it suitable for general measurements in the broadcast band. Kit includes pre-drilled chassis, a 100 foot spool of #24 AWG hookup wire, A 3.5 inch diameter pre-drilled ABS form cut to 4.1 inches in length, 10-32 nylon hardware for mounting, other hardware, and manual that includes measurement applications. Self capacitance of a coil can be determined using the two frequency measurement method and the following equation.

    Co = (C2 - 4C1)/3, {all in pf}


    250 uH Coil Specification
    dia 3.55 inches
    length 3.05 inches
    form 4.1 inches
    turns, (N) 61  
    Co 8.6 pf
    Fo 4.15 MHz
    Q 193 @ 1 MHz
    wire #24 pvc

    where C2 is the capacitance at resonance at frequency F2; and , C1 is the capacitance at resonance at F1 (wherein F1 = 2* F2). Details, including derivation of the equation, can be found, as mentioned above, in The Xtal Set Society Newsletter, September, 2007.

    The Standard 250 uH Coil Kit
    Qty: Price: $18.95