1. Click for the old QRP HomeBuilder Graphics page.  Click for my Pin Outs page.  Click for my Homepage

2. Some simple tools written in JavaScript for the QRP/SWL HomeBuilder:
    Minimal input error checking

A.  Calculate DC Voltage Divider Bias
DC Bias
Enter Voltage:    Enter R1:   Enter R2:      Bias voltage  =  

B.  Calculate Inductive Reactance

Enter Inductance in uH:    Enter Freq in MHz:      XL (ohms) =  

C.  Calculate DC Current for a Current Mirror
Current mirror
Enter VCC:    Enter RC in ohms      Current (mA) =  

D.  Calculate # of Turns To Obtain a Desired Inductance on a Ferrite Torroid
Calculate turns for a ferrite core
Enter Inductance in millihenries:    Select Core:        Turns  =  
The AL for this ferrite core is   =  

E.  Calculate Cut off Frequency for an RC Low Pass Filter

Enter resistor value in ohms:    Select capacitor values in uF:         3 dB down frequency (Hertz)  =  

F.  Calculate Power in dBm and mW from Peak to Peak Voltage

Enter measured peak-to-peak voltage into a 50 ohm load:           dBm,     mW

Application Note: This web site follows the EMRFD standard for dBm power measurement. dBm = the power delivered into a 50 Ohm resistive load which is temporarily substituted at that point in the signal chain

G.  Calculate  Lm and Cm For a Crystal using the G3UUR Method

Enter frequency in MHz written on crystal (series resonant frequency):

Enter measured frequency in MHz with switch open:  Enter measured frequency in MHz with switch thrown:

Enter crystal capacitance in pF:  Enter open switch circuit capacitance in pF

    Cm   =    femto Farads ,  Lm  =   Henries

Supplemental web page for this applet: Crystal filter measurement and adjustment  Link

H.  Calculate Decibel Power Gain or Loss from 2  Peak-peak Voltages

Enter voltage 1:    Enter voltage 2      dB gain or loss =  

I.  Calculate Decibel Power Gain or Loss from Input and Output power 

Enter input power in watts:    Enter output power in watts      dB gain or loss =  

J.  Calculate dBm and mW from RMS Voltage (50 ohms)

Enter RMS voltage            dBm       mW

K. Calculate Return Loss and VSWR (50 Ohms Detector) 

Enter the detector signal in pk-pk volts when the unknown port is terminated in an open circuit:    Enter the detector signal in pk-pk volts when the unknown port is terminated in the unknown impedance: 

    Return loss =   dB,   VSWR=1:   

Measurements per Figure 7.41 EMRFD. Schematic here

L.  Calculate Power from the DC Output of an AD8307 Meter

1. Linear calibration steps:

Enter measured DVM voltage at -10 dBm:    Enter measured DVM voltage at -20 dBm:   

2. Calculate power in dBm from DVM voltage:

Enter measured DVM voltage:           Power  =  

M.   L-C-C Tee Network

Enter frequency in MHz: 

Enter R1 in Ω:     Enter R2 in Ω:      R1 must be < R2, but the network is bi-directional

Enter Q:       Perhaps start with 2-5

      C1 =   pF,  C2 =   pF,  L =   uH

N.  Parallel Resistor Values   (2-4 resistors)

Enter R1:    Enter R2     Enter R3:    Enter R4:   

        R =   ohms

O.  LCR -- a Reactance Calculator    In beta -- do not use !

Mode:    Inductance:    Enter frequency in MHz