Inductors Introduction


In this phase, the builder undertakes the most tedious part of the build, the winding, installation, and testing of the 4 coils and the transformer.

Note that, while the schematic calls for a L5 coil, this has been eliminated as not needed/used in the 6m, 4m, and the 2m versions.

The inductors are band-specific items and their values and turn counts will depend on which version of the converter you are building (6m, 4m, or 2m). In the installation tasks below, the band-specific items are separated out into band-specific "Bill of Material" (BOM) pages for your convnience.

The inductors are tested for continuity following installation, using points on the board physically removed from the actual solder joints of the inductor's leads, but still electrically connected via the board traces.

1 turn Remember, when winding toroidal inductors, a single pass through the core counts as 1 turn. You might want to review Leonard KC0WOX's excellent 10-minute video on winding toroidal coils and transformers.

Also, please refer to the common component mounting instructions for toroids

Inductors Schematic

(Resistor testpoints (hairpin, top, or left-hand lead), as physically installed on the board, are marked in the schematic with red dots)

(Click for Full Schematic)

Inductors Bill of Materials

Stage Bill of Materials

(resistor images and color codes courtesy of WIlfried, DL5SWB's R-Color Code program)

L1band-specificmisc  Inductors
L2band-specificmisc  Inductors
L3band-specificmisc  Inductors
L4band-specificmisc  Inductors
L5band-specificmisc L5 is unused in current designInductors
T1band-specificmisc  Inductors
T25-12T25-12 toroid coregreen greentoroid  Inductors
T25-6T25-6 toroid coreyellow yellowtoroid  Inductors
wire26#26 magnet wirewire  Inductors
wire30#30 magnet wirewire  Inductors

Band Specific Items for 6m Band

L10.35uH 11T #26 on T25-6(yellow) (7")yellowcoil  Inductors
L20.35uH 11T #26 on T25-6(yellow) (7")yellowcoil  Inductors
L30.35uH 11T #26 on T25-6(yellow) (7")yellowcoil  Inductors
L40.78uH 17T #30 on T25-6(yellow) (9")yellowcoil  Inductors
T10.53 uH 14T/2x7 bifilar #30 on T25-6(yellow) (8")yellowtransformer  Inductors

Band Specific Items for 4m Band

L10.22uH 9T #26 on T25-6(yellow) (7")yellowcoil  Inductors
L20.22uH 9T #26 on T25-6(yellow) (7")yellowcoil  Inductors
L30.22uH 9T #26 on T25-6(yellow) (7")yellowcoil  Inductors
L40.53 uH 14T #30 on T25-6 (10")yellowcoil  Inductors
T10.13uH 7T/2x4 bifilar #30 on T25-6(yellow) (6")yellowtransformer  Inductors

Band Specific Items for 2m Band

L10.08uH 6T #26 on T25-12(green) (5")greencoil  Inductors
L20.06 5T #26 on T25-12(green) (4")greencoil  Inductors
L30.06 5T #26 on T25-12(green) (4")greencoil  Inductors
L40.53 uH 14T #30 on T25-6 (10")yellowcoil  Inductors
T10.13uH 7T/2x4 bifilar #30 on T25-6(yellow) (6")yellowtransformer  Inductors

Inductors Summary Build Notes

Inductors Detailed Build Notes

Top of the Board

Inductors Top View

Wind and Install Coils

Wind and Install coils L1, L2, L3, and L4

Note: L5 is not required on any of the manifestations of the current design.

L5 is unused in current design
6m L40.78uH 17T #30 on T25-6(yellow) (9")yellowcoil  
6m L30.35uH 11T #26 on T25-6(yellow) (7")yellowcoil  
6m L20.35uH 11T #26 on T25-6(yellow) (7")yellowcoil  
6m L10.35uH 11T #26 on T25-6(yellow) (7")yellowcoil  
4m L40.53 uH 14T #30 on T25-6 (10")yellowcoil  
4m L30.22uH 9T #26 on T25-6(yellow) (7")yellowcoil  
4m L20.22uH 9T #26 on T25-6(yellow) (7")yellowcoil  
4m L10.22uH 9T #26 on T25-6(yellow) (7")yellowcoil  
2m L40.53 uH 14T #30 on T25-6 (10")yellowcoil  
2m L30.06 5T #26 on T25-12(green) (4")greencoil  
2m L20.06 5T #26 on T25-12(green) (4")greencoil  
2m L10.08uH 6T #26 on T25-12(green) (5")greencoil  

Wind and Install Transformer

Wind and install T1

You should review the materials in the pdf file Winding_T1_for_the_20m_SR_Lite_II, which depicts winding and installing a toroidal transwformer (the 8x2 transformer was for the Softrock Lite II, but the techniques are the same here, with the turn counts being different).

Take care in winding and installing this transformer, since it has a real effect on image rejection issues that might be experienced in operation once completed.

6m T10.53 uH 14T/2x7 bifilar #30 on T25-6(yellow) (8")yellowtransformer  
4m T10.13uH 7T/2x4 bifilar #30 on T25-6(yellow) (6")yellowtransformer  
2m T10.13uH 7T/2x4 bifilar #30 on T25-6(yellow) (6")yellowtransformer  

Inductors Testing

Test coils L1-L3 for Continuity

Test Setup

With power OFF, test for continuity between the numbered test points (they are numbered in the bottom view as 1 thru 3, corresponding to L1 - L3).

Test coils L1-L3 for Continuity

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
Testpoints numbered 1ohms0.00.0_______
Testpoints numbered 2ohms0.00.0_______
Testpoints numbered 3ohms0.00.0_______

Test L4 and T1 Continuity

Test Setup

Test L4 continuity by checking the resistance between the points labeled 4 on the topside view.

Similarly, test the continuity of the primaries and secondaries of T1 by probing points "P" and points "S" with your ohmmeter (the points have black letters on a yellow background dot).

Test L4 and T1 Continuity

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
Testpoints "4"ohm0.00.0_______
Testpoints "P"ohm0.00.0_______
Testpoints "S"ohm0.00.0_______