Progressive Receiver Design - Tuned Circuit Data

Freq. Low

Freq. High

C1

pF

C2

pF

C3

pF

C4

pF

C5

pF

C6

pF

C7

pF

C8

pF

L1

uH

T1

uH

T2

uH

0.45Mhz *

0.46MHz

10-100

100

2200

6800

6800




82



1.8

2.0(a)

10-100

10

470

1500

1500




20



1.8

2.0(b)

5-50

10

270

820

820




35



3.5

3.8

5-50

47

270

470

470




8.5



7.0

7.1

5-10

33

100

330

330




4.5



9.0 *


9-10

22

100

330

330




3.3



10.0

10.15

5-10

22

82

220

220




2.9



14.0

14.35

5-10

18

68

220

220




1.83



18.06

18.17

5-10

18

47

180

180




1.3



21.0

21.45

5-10

18

47

180

180




1.0



24.89

24.99

5-6

15

33

150

150




0.90



28.0

29.7

5-11

12

33

100

100




0.71



50.0

52.0

5-9

10

22

100

100




0.30



Notes:

Suggested winding details are shown below.

The inductance values for T1 and T2 are for the tuned winding.

All frequencies in MHz unless otherwise stated.

Capacitor C1 is shown in the form minimum value - maximum value.

The values shown for 450-460KHz and 9MHz are suggested values when the NE602 is used as a product detector in a superhet receiver. Constructors might like to try ceramic resonators instead of conventional tuned circuits on these frequencies.

Coil Assemblies:

If constructors wish to wind their own inductors and transformers there are a variety of new and second hand coil assemblies available from the amateur radio market. The most common types are in ½ inch square aluminium cans, approximately ¾ inch high which are available from rallies and surplus suppliers in the form of assembled PC boards out of mobile radio equipment. Half inch diameter iron dust toroids may be used but will require tuning with trimmer capacitors and only limited details have been provided.

Finished coil assemblies should be tested and then the windings varnished and left to dry for at least 24 hours - clear polyurethane varnish is suitable for this purpose. To retain the adjustable core a small amount of silicon tap grease may be put into the former thread prior to assembly - do not use a grease that contains any metallic or conductive compounds.

For use in a 50ohm environment transformers T1 and T2 should have a turns ratio of between 8:1 and 10:1 between the tuned winding and the coupling link - the coupling link is wound over the cold or earthy end of the tuned winding. The tuned winding is connected to the tuning capacitor C6 or C8 and the coupling link to the aerial or receiver circuit.

Transformers T1 and T2 form a bandpass filter, slightly overcoupled on some bands in order to cover the whole of each band without retuning.

The following table gives coil details (Toko part numbers where available from one or more UK suppliers) and suggested winding details for use with the ½ inch square assembly - capacitor values as shown on the first page:

Frequency Range

L1

T1

T2

450-460KHz

68t, 7/48# Litz wire plus a pot core



1.8-2.0MHz (a)

65t, 7/48# Litz wire



1.8-2.0MHz (b)

79t, 7/48# Litz wire



3.5-3.8MHz

40t, 7/48# Litz wire



7.0-7.1MHz

23t, 36# wire



9.0MHz

27t, 36# wire



10.0-10.15MHz

KANK 3335

23t, 36# wire

KANK 3335

KANK 3335

14.0-14.35MHz

17t, 30# wire



18.06-18.17MHz

14t, 30# wire



21.0-21.45MHz

12t, 30# wire



24.89-24.99MHz

12t, 30# wire



28.0-29.7MHz

11t, 30# wire



50-52MHz

7t, 26# wire



Winding wire should be solderable-enamel covered copper wire. The 7/48# Litz wire is seven strands of 48# enamelled wire with an outer covering of cotton and gives a higher Q value than single strand wire. If Litz wire is not available use 40# (swg) single strand wire.

Each winding should be close-wound and take up no more than two thirds of the former length. If more space is required then the winding should be scramble wound back and forth over itself until the required number of turns has been achieved.

Make each winding off to the base pins by pre-tinning the wire before threading it into each pin and soldering in place. Test each coil before applying any varnish.

Additional oscillator coil information has been provided by project participants as follows (frequencies in MHz):

Freq. Low

Freq. High

C1 pF

C2 pF

C3 pF

C4 pF

C5 pF

L1 uH

6.97MHz

7.105MHz

8-30

330

110

390

390

13t, 26swg, enamelled copper wire on T50-6 toroid

13.6

14.4

8-30

39

56

220

220

KANK3335 1.5uH

13.95

14.5

8-30

110

56

220

220

KANK3335 1.5uH

16.8

19.5

8-30

0

56

220

220

KANK3335 1.5uH

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