SW3 and SW5 Coils

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.


Back to W0VLZ's Radio Bay