Quick and Easy Bandpass Filters for Receiver Input Tuning - George Dobbs G3RJV

“READY-DESIGNED” DUAL TUNED BANDPASS FILTERS [50 ohms input/output] A series of Bandpass Filters designed for the input tuning of amateur band receivers by G QRP Club member Stefen Niewiadomski from his book The Filter Handbook. The filters are designed for 50 ohm input/output impedance and may be cascaded for better roll-off outside the passband. The TOKO coils also have a tap on the tuned winding which is useful for matching into input circuit of the order of 1k ohm. The designs use off-the shelf TOKO coils. The designations for the coils are the part number available in the UK. These can be ordered direct from the USA - see below. The inductors are variable [core tuned] but the mean inductance is given for matching to other inductors. From : The FILTER HANDBOOK Stefen Niewiadomski Heineman Newnes 1989 ISBN 0-434-91378-2

BAND
MHz

T1 - T2
TYPE

T1 - T2
Inductance

C1 - C3
[pF]

C2
[pf]

1.8 - 2.0

3333

45uH

150

12

3.5 - 3.8

3333

45uH

39

3.3

7.0 - 7.1

3334

5.5uH

100

8.2

10.1 - 10.15

3334

5.5uH

47

6.8

14.0 - 14.35

3334

5.5uH

22

3.3

18.07 - 18.17

3335

1.2uH

68

6.8

21.0 - 21.17

3335

1.2uH

47

4.7

24.89 - 24.99

3335

1.2uH

33

3.3

28.0 - 29.7

3335

1.2uH

22

3.3

T1 & T2 Inductor Types : KANK3333R, KANK3334R, KANK3335R

 

The named inductors are available in the UK from MAPLIN [sales@maplin.co.uk] A suggested US supplier for designated TOKO coils is PENSTOCK [800] 736-7862