Most of the old articles I have found, with the exception of receivers using slider-tuned inductors, call for x turns of a particular gauge of cotton or silk covered magnet wire on a coil form of y diameter (#22 DCC seems to have been a favorite). Given the scarcity of silk and cotton covered magnet wire, is there a formula or table available that will allow me to wind coils of the correct inductance with enameled wire? I know length is a factor as well as diameter and number of turns (yes, I still remember the formula for winding solenoidal air-cored coils from my days of crystal set experimentation in high school), but I have no idea what the diameters of the various gauges of cotton or silk insulated wires were so I can figure them into the equation and know what the inductance of the "original" coil was supposed to be.

You can try Litz for a "deluxe" coil:

http://makearadio.com/coils/cylindercoils.php

Or just use enameled wire and the Professor Coyle calculator:

http://www.crystalradio.net/professorco ... ecyl.shtml

Depending on the variable capacitor you have, if you want to cover the whole AM band, you will need something like 240 to 300 microhenries inductance.

Rich

I will probably be using the "standard" 365pF variables that are still being made.

The number of turns for cotton, silk is the same for enamel. It is the spacing that is the problem. In the solenoid the adjacent tuns add capacitance which decreases the natural resonance of the coil. Cotton wire and silk because of the thicker insulation will have a higher resonances for the same number of turns and diameter form... That said, manufacturers could use a variety of denier in the covering textile and vary the angle of the wind. Generally, that would control the thickness of the textile insulation. There was no set rule for the denier or angle of lay. Therefore no specific calculation could suffice to equate between textile covering specified and enamel. Space winding enamel is a choice the builder can make to control the capacity of the coil.

Small gages of textile covered magnet wire have a larger percentage of the diameter as insulation. Best suggestions as an experimenter. Wind the coil with magnet wire and determine the inductance. Note the other tuning element that may be involved and calculate the wavelength range the the tuned circuit should select. Try space winding so that the tuner will cover the entire BC band with the variable condenser fully open...

Alternately, cotton covered wire is still available from ebay vendors and others that frequent the Forum.

BTW If you have any A-K tuner elements kicking around, these are ready made for experimenting... enamel wire.

Chas

As a matter of fact, I have a junk chassis for an Atwater Kent 35 that still has all the RF coils and tuning capacitors.

Wind a coil with parallel enamel wire, then apply Q Dope and unwind the dummy wire as the dope starts to set. The dummy can be whatever diameter you want.

Or wind with both in a vise an under steady tension. Secure the form in another vise, cut the ends of the dummy and unwind and then apply the dope for a neater appearance.

Other times the dummy can be used as the other winding and interlaced as many turns as desired which works well for shortwave plug in coils.

Carl