Basket/spiderweb coil design

The tuning circuits of my xtal sets are made out of old fashioned type of coils as seen in old magazines and photo`s, these can be Honeycomb, Basket weave, Spiderweb and other forms of coils. In German these are: Honigwaben, Korbspule, Spinnwebenspule. Basket weave coils are also mentioned in books as "Lorenz" coils, and can be made in different shapes and sizes, as the Honeycomb and Spiderweb coils.

These coils were made because of their low own capacitance, this gives your coil a higher Q because the windings are further apart from eachother, there is more air between the layers.

You can make your coils using enameled copper wire, or silk or cotton insulated wire. Better if you make coils for the middlewave band using Litze wire, this wire is made out of many insulated smaller wires, from 3 up to 1500 or more small wires. But the more wires, the more expensive the wire.

A honeycomb coil is not more then a one layer cilinder coil. Many variations are made of this type of coil. After many tests and research they came to the conclusion that the selfinduction is going through a maximum when the cross section has a rectangular form (Thickness is same as width) like in fig.19 is the same, and when the average diameter is the same is 3x the thicknes of the winding.

Calculation of Spiderweb/basketweave/cilinder coils can be done with the "prof. coyle" programme, but I didn`t find a formule to calculate honeycomb coils, these calculations were so complex they only published the data to create these honeycomb coils. I have the data below as found in old books:

Used capacitor in table 1 is 1000cm (+/-1100pF) wire size 0,5mm. The coil form has a diameter of 5cm, thickness is 4cm.

Number of windings Wirelength Wavelength
180 - 430 meter
200 - 550 meter
250 - 700 meter
400 - 1000 meter
500 - 1300 meter
700 - 2000 meter
1000 - 2700 meter
1300 - 3600 meter
1600 - 4200 meter

Source : Bastelbuch fur radioamateure, 1925

Coilform in table 2 is 5cm in diameter and a width of 2,5cm. Own wavelength is the wavelength of the coil with its own capacitance.
Number of windings Induktion in "milliHenry" Own wavelength  in meters (approx) Wiresize in mm Wirelength in meters  (approx) Range with C of
50pF-1000pF  in meters
4 meter
6 meter
9 meter
14 meter
20 meter
30 meter
40 meter
50 meter
60 meter
80 meter
120 meter
225 meter
  90 - 400
120 - 550
175 - 750
  250 - 1000
  300 - 1500
  500 - 2000
  650 - 3000
  800 - 3500
1000 - 4500
1250 - 6000
1500 - 7000
  3000 - 15000

Source: Der radioempfangsapparat, 1924 

Coils as in the upper tables are made on a coilform as seen on description and photo`s below, but you can alter these by varying number of pegs used.

The Honeycomb coil

Coil form with its measurements are in the following drawings. You can use your own measurements and  the number of pegs. But the above values are for these coils here.
You can make your form out of wood, but I made it out of alluminium on a lathe, the pegs are made out of knitting pins, bought these at the weekly market here, if you buy these with 2 pointed sides you can make two pegs of `m, so you need to buy half of the knitting pins you need for the coil form.

A Honeycomb coil is getting larger in diameter the more layers are wound on it, but the width stays the same.

You can use your own style the make your coil,...over2/under2, over2/under3, over3/under2. Do it as you like and look at the results.

Winding method seen at the left: Over1/under 4.

If you use only one side of the coil form, you can wind your spiderweb coil on this coilform, but you have to fix it with glue, the needlework will not work here.


November 2010
On a lathe I made two new coilforms to wind coils. Both have two rows of 15 holes in it to put in some knitting pins to wind the wire around.
The sizes are as mentioned in old books for the coils mentioned above, one 4.5cm thick and one 2.5cm thick with a inner diam of 5cm.

Winding method: Over two, directly to other side and again over two at the other side. (over 2/under 0)

I wound the smallest coil mentioned above (2.5cm wide). Precisely according the description in the books with 25 windings. The value should be 50µH, but after I measured it with my AADE meter and another LCR bridge the value was around 122µH. Same for wire length, I took 4 meters and wound the coil till I got no wire left,..8 windings with a value of 12µH. So just wind your coil, measure and put some more wire on it or take some windings off till you get what you want.


For the above honeycomb coil I made a table for future use when I need to make some coils. I made 3 and put the value and windings on mm-paper, I connected the points to get a rough guess of inbetween points.
Then I made the coils I needed and measured them and also put them inside the table. It only goes to 162µH because I didn`t wind a bigger one.

Table is for honeycomb coils using the "Over2/Under0" method, wound onto a 5cm in diameter form, 2.5cm wide with 2x15 pins.

The basket weave coil.  (lorenz coil)


You can create your basket weave coils using a piece of wood  or something. I used a piece of plexiglass with a thickness of around 1cm and drilled holes in it, I used steel nails to put in the holes. The nails are placed in a cicle of around 12cm. I wound the wire around the nails using the over1/under2 methode. But this can be re-arranged by you using anothe method,..over1/under1, over1/under3, name it.

Right over1/under2

Left over2/under1

Another type of coil is the basket weave coil made using two rings of nails to wind your wire through. At the right you see 2x11 steel nails. The methode of winding here is over2/under2, but you also can use over1/under2 or something else.

Note: Of you follow the wire in the over2/under2 methode, you get to the starting point after 3 circulations of the wire. Now you layed down just one layer. This also includes the coils mentioned above.
This is what they mean by the windings do not see eachother, there is lots of air between every layer, this gives you a coil with a better Q.

This way I made several basket weave coils and some of these had one layer after 8 windings.

In table 1 they used 25 windings and 4meters of wire on a coilform of 5cm in diameter. These 25 windings are the windings,..not the layers. You have to watch out not lay down 25 layers.

A basket weave coil stays the same diameter while the width is getting more.


Below some pictures of coils I made and on their form. (this is my first and old coilform)

My homebrew coilform.

Coil being made using the form with knitting pins

Close-up of the coil

This coil is not glued, but I did some needlework. 

Honeycomb coil
Spiderweb coil

3D coil made on a 1mm thick piece of "trespa"

Side view of the 3D coil

10 layer Honeycomb coil, made out
of 0,75mm thick enameled wire. Fixed
using shellac and zapon laquer.

Pictures of coils are made by me. © 2005

Fixation of the coils so they do not fall apart can be done using some needlework, another used methode from the beginning of the 20th century is to fix the coil using "zapon-laquer". This a laquer on a nitrocellulose basis. Long time ago you could make this yourself by dissolving celluloid film negatives into ethanol. Beware: film negatives these days are not made out of celluloid. Now you submurge the coil into the solution you get and after that you get it out of the solution and let it dry. You also can use "shellac" to fixate the coils, this is available plentyfull on Ebay,..a kilo for 8 Euro`s or so.

Self resonance of coils

I made a cilinder aircoil with a value of 15µH. Without a capacitor connected I measured the resonance of this coil. It was resonant at 11.110Mhz. -3dB point was at 11.220 and 10.930, this makes a bandwidth of 290khz.



So this is the frequency where the coil is resonant with it`s own capacitance. The Q of this coil is 11.110mhz/0.29mhz=38
Not really a good choise to use for a chort wave crystal receiver.


Its own capacitance is approx. 13pF.
If I use this coil on shortwave, the selectivity would go any better then this 290khz. Q is only getting better at a lower frequency.






I also measured the self resonance of my 440x46 spiderweb coil of my 2006 BTTF receiver.
Resonant at 2.523Mhz, -3dB point at 2.539 and 2.505Mhz, this makes a bandwidth of 34Khz.
The Q of the coil at this frequency is 2.523/0.034=74.
Here I see that the Q is much better at lower frequency as i measured in another chapter on my site.
Self capacitance is around 16pF

If I wanted to make myself a 10-15Mhz shortwave crystal receiver with a bandwidth of around 9Khz, then I
would have to use a coil with a Q of around 1300, this means a self resonance point that is at a much higher level, and
a even lower capacity,..even lower as 5pF,..I still want to seperate the station,..won`t I.

I also made a aircoil out of 6mm copper brake piping, 11cm in diameter, 8 windings, space between winding is 6mm.
These type of coils were used very often in old radio equipment.
Self resonance at 17.690Mhz, -3db point at 17.980 and 17.350, makes a bandwidth of 630Khz.
Q of this coil at 17.690Mhz is 17.690/0.63=28

How do I get I veeery high Q at shortwave,..I think never, even a aircoil I made with a diameter of 25cm
had a low Q.


I also made myself a coil winder according to the Gingery Coil Winder manual. With this type of winder you can make yourself some nice small radio coils for your project. Below a small movie I found on the internet on how the coil winder works.


Another type of coilwinder is seen here and here

The coil winder in the above links are in principle the same as the Gingery winder, only the cam has been changed into a heart shaped one. This type of cam has the advantage that the wire does go around the circumference of the coilform in a triangle shaped fashion, instead of a sinus with the round excentric cam. The heart shaped cam gives the coil a much higher stability when winding the coil. Below a scan from WM. Querfurth`s book of the heart shaped cam with the round excentric cam in red to compare the two cams.

Cheap litze wire I bought from:

The better choise of Litze wire is from  "Pack - feindrähte" in Germany. There also is a
retailer of Pack in the Netherlands. The company "Huibers" from Amerongen.
Litze I use is Rapulit®classic.

Idea`s and descriptions on.  
Another coil description   

Trefwoorden: honingraatspoel, Korfbodemspoel, Korbbodenspule, Honigwabenspule, Honeycomb coil, flachspule, Spinnwebenspule, spiderweb coil, zaponlack.