The National SW3, SW5, SW34, SW58 and SW45 all share a coil design characterized by three independent windings and a unique 6 pin base. These coils are enough alike that they tend to be confused. Besides the obvious frequency coverage differences, some are designed for the RF stage while others work best in the detector stage. Also, as National upgraded the tube lineup, the number of turns in the tinkler/antenna winding were reduced.
The table below catalogs these coils.
Series Series Series 10-20 60-70 30-40 RF Tube 35/34/32/24/36 58/6C6 6J7/1N5 Detector Tube 35/34/32/24/36 58/6D6 6J7/1N5 ****************** General Coverage Coils ************************ Range MHz .09-.16 22 72 42 .15-.22 21 71 41 .19-.28 20 70 40 .25-.39 19 69 39 .32-.65 18(Purple) 68 38 .50-.90 17(Yellow) 67 37 .69-1.5 16(Orange) 66 36 1.5-2.7 15(Blue) 65 35 2.5-4.5 14(Green) 64 34 4.2-8.0 13(White) 63 33 7.0-12.0 12(Red) 62 32 12.0-21.0 11(Black) 61 31 19.0-35.0 10(Brown) 60 30 ******************* Bandspread Coils *************************** Range MHz 1.7-2.2 15A(Blue) 65A 35A 3.5-4.0 14A(Green) 64A 34A 7.0-7.35 13A(White) 63A 33A 13.9-14.4 11A(Black) 61A 31A 27.0-30.0 10A(Brown) 10A 30A Notes: Bandspread coils have a pigtail that goes to the grid caps of the RF and detector tubes. The bandspread detector coils have a padding capacitor for calibration adjustment.
The coil forms used are made of National R39 material, which ensures the minimum loss at these high frequencies; this material is far superior to ordinary bakelite. The tickler coil may be wound in the slot at the bottom of the National form; the primary winding can be wound in between the turns of the secondary as shown in the diagram below.
The secondary winding of the coils is shunted by 90 mmf. (.00009 mf.) variable condensers. Diameter of the coil forms is 1 1/2 inches:
| Coil Number | 10 - Brown |
| Frequency | 9 to 15 meters (20-33.3MHz) |
| Secondary | 2 5/6 turns of No. 16 Enamel |
| Primary | 1 5/6 turns of No. 34 Enamel |
| Tickler | 3 turns of No. 32 Double Silk. |
| Coil Number | 11 - Black |
| Frequency | 14.5 to 25 meters (12-20.7MHz) |
| Secondary | 6 1/4 turns of No. 16 Enamel |
| Primary | 3 5/6 turns of No. 34 Enamel |
| Tickler | 3 turns of No. 32 Double Silk. |
| Coil Number | 12 - Red |
| Frequency | 21 to 41 meters (7.3-14.3MHz) |
| Secondary | 11 5/6 turns of No. 18 Enamel |
| Primary | 7 5/6 turns of No. 34 Enamel |
| Tickler | 3 turns of No. 32 Double Silk. |
| Coil Number | 13 - White |
| Frequency | 40 to 70 meters (4.3-7.5MHz) |
| Secondary | 19 5/6 turns of No. 18 Enamel |
| Primary | 12 5/6 turns of No. 34 Double Silk |
| Tickler | 4 turns of No. 32 Double Silk. |
| Coil Number | 14 - Green |
| Frequency | 65 to 115 meters (2.6-4.6MHz) |
| Secondary | 34 5/6 turns of No. 24 Enamel |
| Primary | 21 5/6 turns of No. 34 Double Cotton |
| Tickler | 4 turns of No. 32 Double Silk. |
| Coil Number | 15 - Blue |
| Frequency | 115 to 200 meters (1.5-2.6MHz) |
| Secondary | 62 5/6 turns of No. 28 Enamel |
| Primary | 38 5/6 turns of No. 32 Double Silk |
| Tickler | 5 turns of No. 32 Double Silk. |
The majority of this information is from the AWA Old Timer's Bulletin, Vol. 34 issue 3. This magazine (with other interesting articles) is available from the AWA.