In this post I want to add some miscellanies about the project.
For those interested in repeat my line of thinking, this is an easy and simple program made for MS DOS QBASIC, which helped me to obtain a better values for the circuit elements of the oscillator and RF stages, but I suppose than can also be adapted to another programming language, surely more modern that this.
Here is the code used:
/code:
CLS
LET Tc = 16 { Value in Farad of the trimmer capacitor }
LET P = 552 { Value in Farad of the padder capacitor }
LET Tl = 38.4 { Value in Farad of the fixed capacitance in the oscillator coil }
LET Lo = .000089 { Value in Henry of the oscillator inductor }
LET Fi = 465000 { Value in Hertz of the intermediate frequency amplifier }
LET Ls = .0001885 { Value in Henry of the antenna and RF tuned inductor }
LET Ct = 37.4 { Value in Farad of the antenna trimmer capacitor plus fixed and starys }
PRINT "Fsint", "Cosc", "Fosc", "FI conv.", "Error"
FOR i = 1 TO 21
READ G { Step Gang capacitance read from data statements }
LET Cs = Ct + G { Total capacity in the RF section: gang (Read from data statements), trimmer and stray }
LET Fs = 1 / (6.28 * SQR(Ls * (Cs * 1E-12))) { Incoming signal frequency }
LET Co = Tl + (((Tc + G) * P) / (Tc + G + P)) { Total capacity in the oscillator section, gang (Read from data statements), trimmer and stray }
LET Fo = 1 / (6.28 * SQR(Lo * (Co * 1E-12))) { Oscillating frequency }
LET Fic = Fo – Fs { Intermediate frequency obtained }
LET DFi = Fi – Fic { Intermediate frequency error respect to the wanted }
PRINT Fs, Co, Fo, Fic, DFi
NEXT i
DATA 12,25,50,75,100,125,150,175,200,225,250
DATA 275,300,325,350,375,400,425,450,475,500
/end code.
The first sentence clears the screen between tests. Then, in the following, I load the fixed values of some constants that will not be changed in the program. Following it, a simple titles for the columns of results from the computations below them.
A for – next loop for the total points of the gang capacity for which is wanted to estimate the tracking error. The capacity values to be read are stored in the data sentences at the end of the program. With this value, simple frequency calculations are made for oscillator and incoming signal paths, and checked (substracted) to obtain the final error.
Bibliography:
F. Langford Smith “Radio Designer’s Handbook”, 1997.
George E. Valley and Henry Wallman “Vacuum Tube Amplifiers”, 1948.
Samuel Seely “Electron-Tube Circuits” 1950.
ARRL “Radio Amateur’s Handbook”, 1949 (Version in Spanish).
Héctor Algarra y Alberto Rodríguez “La Técnica del Receptor de Televisión” (In Spanish).
Some patents in PDF format at Google Patents, Advanced Search.
Tubes data sheets found in the Internet from Google Search.
Software:
MS DOS 7.10 edit.com
Microcap IV (For DOS) (Simulation program for DOS’ers)
Microsoft Word, Office 97
LT Spice (From http://ltspice.linear.com/software/LTspiceIV.exe)
Microsoft Paint.
Express PCB and Schematic capture at http://www.expresspcb.com
Adobe Acrobat Reader from http://www.adobe.com
Thanks to Luciano Alvarez LW1EL for support my large comments and crazy ideas almost every Sunday nights at the QAP frequency.