W3NQN Multiband Transmitting BPF Project

 

Completed Filter

All cable connections are made to the rear apron. An auto/manual rotary select switch together with LED indication of filter selected is available on the front panel, as shown below:

A desire to improve upon the performance of commercially available multiband transmitting BPFs whilst at the same time simplifying rig interface and antenna select mechanisms, led to the conception of this project. Interest among other contesters made commercial production of high quality printed circuit boards economically viable.

Features

 

Filter Performance Measurements

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These were made using an HP8568B spectrum analyzer and HP8444A tracking generator. Plots for each of the filters follow:-

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160m - Insertion loss 0.4dB. 2f attenuation 48dB.

80m - Insertion loss 0.3dB. 2f attenuation 50dB. f/2 attenuation 45dB.

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40m - Insertion loss 0.4dB. 2f attenuation 60dB. f/2 attenuation 45dB.

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20m - Insertion loss 0.4dB. 2f attenuation 57dB. f/2 attenuation 40dB.

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15m - Insertion loss 0.4dB. 20m attenuation 35dB. 10m attenuation 48dB.

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10m - Insertion loss 0.4dB. f/2 attenuation 45dB. 15m attenuation 25dB.

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Performance Comparisons

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The following table incorporates our prototype figures into a table produced by Peter Pfann, DL2NBU when he built W3NQN filters for the Bavarian Contest Club in 2002. The table provides useful comparison with sample filters from Dunestar and ICE.

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Frequency

1.81-1.89

3.50-3.80

7.00-7.20

14.0-14.35

21.0-21.45

28.0-29.0

10m Dunestar

10m ICE

10m DL-NQN

10m 5B-NQN

53dB

74dB

72dB

80dB

48dB

71dB

69dB

80dB

43dB

65dB

74dB

70dB

41dB

36dB

38dB

45dB

35dB

16dB +

18dB +

25dB

0.9dB * +

0.4dB

0.4dB

0.4dB

15m Dunestar

15m ICE

15m DL-NQN

15m 5B-NQN

50dB

73dB

76dB

80dB

45dB

61dB

78dB

80dB

40dB

46dB

58dB

60dB

43dB

21dB +

28dB

35dB

1.0dB +

0.3dB

0.4dB

0.4dB

51dB

11dB +

60dB

48dB

20m Dunestar

20m ICE

20m DL-NQN

20m 5B-NQN

48dB

66dB

75dB

75dB

43dB

70dB

61dB

60dB

40dB

39dB

38dB

40dB

0.8dB +

0.4dB

0.4dB

0.4dB

45dB

19dB +

43dB

38dB

45dB

29dB

32dB

57dB

40m Dunestar

40m ICE

40m DL-NQN

40m 5B-NQN

48dB

77dB

67dB

70dB

51dB

35dB

42dB

45dB

0.6dB +

0.5dB

0.4dB

0.4dB

49dB

25dB

82dB

60dB

44dB

34dB

56dB

50dB

45dB

43dB

47dB

45dB

80m Dunestar

80m DL-NQN

80m 5B-NQN

50dB

40dB

45dB

1.0dB +

0.4dB

0.3dB

37dB

53dB

50dB

58dB

65dB

60dB

32dB

53dB

50dB

23dB

39dB

40dB

160mDunestar

160m DL-NQN

160m 5B-NQN

1.2dB +

0.3dB

0.4dB

35dB

48dB

48dB

57dB

90dB

>80dB

33dB

65dB

60dB

24dB +

60dB

60dB

19dB +

70dB

80dB

.* Dunestar IL at 28.5MHz. (1.2dB @ 28.75MHz, 2.0dB @ 29.0MHz)

.Best performance is indicated by figures in italics. Figures followed by a + designator signify either <25dB attenuation of another band or >0.5dB insertion loss. These reflect questionable to inadequate performance. The BCC filters were built using air-wound coils at L1 & L2 for 20, 15 & 10m. This was essentially a cost saving measure but happens to provide superior attenuation of signals in the next higher band. However, this benefit comes at a price, as can be seen by comparison with our figures for the next lower band. As the W3NQN topology inherently favours good high side rejection it was considered more important to protect low side performance. Consequently toroidal cores were employed in all six filters.