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

• Self contained unit for the 6 HF contest bands.
• Band filters and associated select relays assembled on individual daughter boards providing for replacement on failure without withdrawing the complete unit from service.
• 100W or 200W rating dependent upon user preference.
• Interface directly with transceivers providing 250mA current sinking band line drivers. E.g Ten Tec Orion
• Optional plug-in band data decoder and antenna relay driver configurable for current sourcing or sinking antenna relay drivers. Band data decode in Yaesu format, providing direct compatibilty with Yaesu binary band data outputs and with the Elecraft K3.
• Configurable for "no filter selected" by-pass or open circuit.
• By-pass low SWR to VHF.
• Front panel rotary band switch for local/remote filter selection with LED indication of band in use.
• Performance compatible with stand-alone W3NQN filters. i.e. Not materially compromised through use of motherboard.
• DB9 connector pin compatible with Dunestar 600 providing for direct substitution where required.
• Configurable for Dunestar compatible +ve or -ve keying .
• 5 Pin DIN connector for control using binary band data.
• 8 Pin DIN connector providing access to antenna select relay drivers.
• RF path via 2 standard SO239 connectors.

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.