By dipl. ing. Tasić Siniša Tasa YU1LM/QRP. All rights reserved, project is free for personal use only

HF/5MHz Receiving and Low Power Transmitting Band Pass-Low Pass Filters for SDR transceivers Genesis G****, AVALA**, ADTRX** and HF transceiver CER-1 By dipl. ing. Tasić Siniša Tasa YU1LM/QRP All rights reserved, project is free for personal use only SDR subject has some specific requirements compared to classic RX/TX design. All SDR receivers as DC (direct conversion) receivers are sensitive more or less to the harmonic receiving. My SDR receivers including receivers built in SDR transceivers AVALA series have also sensitivity to harmonic receiving. I made this test at the very beginning but for the very low frequencies below 2MHz and results was good from my point of view 2-35 db rejection odd harmonics and more than 35dB even harmonics, results are comparable with receivers with moderate input filters. I declare that it is possible receiving with my SDR receivers without input filters and practical experience confirm this but it is partly true. I received very interesting mail from Tim DJ4JM who told me that had been measured results little over 1 db lower sensitivity for third harmonic for DR2A+ 7MHz receiver. I check these measurements again and obtain little better results but only 15dB for third and 34dB for second harmonic. My practical experiences with all my SDR RXs are that harmonic receiving exist and that it is negligible even with my big antenna such 84m delta loop is. Receiving at 1.8MHz band I can hardly detect in the evenings hours presents of very strong broadcast stations from 5 and 7MHz band. Only extremely strong carriers are visible and noticeable. Because of that some kind of filter LP (low pass) or better BP (band-pass) are welcome and they will improve overall characteristics of all previously published SDR RX. The second problem is in connection with SDR transmission. I published several transmitters/modulators with CMOS switches series 74HC453, 74HC466 [1] and all are working better than any other types I tested before when we are talking about linearity at fundamental frequency. This realization has specific that modulator is working digitally that mean it has a lot of odd harmonics also modulated of course lower level than wanted output signal. The problem becomes serious when this spectrum arrives to RF linear power amplifier. To keep on unchanged output spectrum it is necessary to attached amplifier with extremely wide working bandwidth what it is no true in case RF amplifier I am using. All used RF amplifiers have limited bandwidth to 6 MHz maximum. The final results we have even harmonics hardly noticeable in output modulator terminate with resistive termination 5Ohms.The bigger problem is products around output signal which is results this harmonics and unwanted phase shift in RF power amplifier at harmonic frequencies. It is interesting that odd harmonics not third only as we are expecting but higher order 5, 7 become problem (see spectrum at picture below). Builders who first assembled my mono-band SDR transceiver AVALA-1 Bodo DJ9CS noticed problems measuring output spectrum from power amplifier with IRF51. He proposed solution which LP filter which dramatically improve output spectrum see picture below also. I made changes in all my new designs and added LP as option for RX and necessary part for the transmitters section (see new version of AVALA-1 and new AVALA-2). Of course it is possible to add BP filters as best solution but also as most complicate for practically realization. Here down in article there are two proposals for LP and four for BP. All filters are possible solder at PCB layout ADTRX**AVALA** and Genesis*** transceivers or on separate board with RF power amplifier. The filters target specification at start ware: 1. Filters are with maximum IL(insertion loss) lower than 2.5 db with inductors Qo ~6 2. All filter components values have to be standard values. 3. Coils are without taps! 4. Termination return loss S11, S22 have to better as possible target value db (VSWR=1.22). 5. Frequencies harmonically related to central frequency from upper side are attenuated ~2-3dB or more. For BP filters this target value is from the lower side fo/2 ~2-3dB. 6. BP/LP filters have 5Ohms termination impedance and filters are symmetrical structure and it is not important what is input or output. 7. Calculated bandwidth -3dB 5-25% of central frequency 8. All filter BP/LP variation is possible solder at the same PCB AVALA transceivers 9. No tune design with low sensitivity to the components tolerance.

Output spectrum at output SDR transceiver AVALA-1 (Pout 35.67dBm (4.2W) without LP/BP at modulator output Output spectrum at output SDR transceiver AVALA-1 the same conditions as it is on picture up (Pout 38.6dBm (8.2W) ) with 2 L section LP/BP at modulator output

1. LP(low pass) with 2 coils Fc -3dB [MHz][band] L1,L2[uH] C1A,C1B[pF] C2[pF] 2.5 [1.8] 4,7 18 33 5.3 [3,5] 2,2 82 15 8 [5,7] 1,2 47 82 15 [1.1,14],68 27 47 25 [18,21],39 15 27 35 [24,28],33 12 22 57 [5],18 68 12 2.844 MHz -.4375 db 3.515 MHz -24.6 db 5.2896 MHz -3.352 db trans 7.79 MHz.9 db 1 MHz -38.87 db -1 7.12 MHz -58.7 db 1 MHz -74.7 db.1 2.1 4.1 6.1 8.1 1 Picture1. LP (low pass) filter for 1.8MHz and 3.5(5.3) MHz

8.86 -.178 db 14. -.2292 db trans 2.46 MHz -15.7 db 28.15 MHz -33.7 db -1 14.5 MHz -25.96 db 21.6 MHz -46.46 db.1 1.1 2.1 3 Picture2. LP (low pass) filter for 7MHz and 1(14) MHz 25.53 -.5557 db 32.456 MHz -.5398 db 55.943 MHz -29.3 db trans 83.524 MHz -49.4 db 1 MHz -57.39 db -1 36.334 MHz -15.77 db 42.181 MHz -24.47 db 62.341 MHz -44.42 db.1 2.1 4.1 6.1 8.1 1 Picture3. LP (low pass) filter for 18MHz and 21,25,28 MHz

55.94 MHz -.1476 db trans 1 MHz -29.19 db 144.3 MHz -47.39 db -1.1 5.1 1.1 15 Picture4. LP (low pass) filter for 5MHz 2. LP(low pass) with 3 coils Fc -3dB [MHz][band] L1 [uh] L2 [uh] L3 [uh] C1pF] C2[pF] C3[pF] C4 pf] 2.5 [1.8] 4,7 5,6 4,7 12 27 27 12 5.3 [3,5] 2,7 3,3 2,7 56 12 12 56 8 [5,7] 1,5 1,8 1,5 33 68 68 33 15 [1.1,14],68,82,68 18 39 39 18 25 [18,21],47,56,47 1 22 22 1 35 [24,28],33,43,33 47 15 15 47 57 [5],22,27,22 39 1 1 39

2.781 MHz -.1637 db 3.522 MHz 7.2588 MHz -31.1 db trans -81.1 db 2.176 MHz -26.83 db -1.1 2.1 4.1 6.1 8.1 1 4. -.73 db 6.982 MHz -32.46 db trans 1.52 MHz -61.17 db 14.13 MHz.24 db 4.2-26.63 db -1.1 5.1 1.1 15.1 2

7.6 MHz -.2219 db 7.4 MHz -.2291 db 1.1 MHz Graph -15.1 db1 14.2 MHz -41.52 db 21.26 MHz -69.84 db 7.3 MHz -21.4 db 7.39 MHz -22.21 db.1 1.1 2.1 28 15.7 -.2724 db 22.23 MHz -24.21 db trans 28.1 MHz -42.51 db 42.13 MHz -7.38 db 14.48 MHz -22.28 db -1.1 1.1 2.1 3.1 4.1 5

21.542 MHz -.1695 db 36.883 MHz -27.4 db 42.169 MHz -37.28 db trans 54.862 MHz -55.72 db 63.663 MHz -65.6 db 22.3-24.55 db -1.1 2.1 4.1 6.1 8.1 1 33.91 MHz -.2649 db 55.94 MHz -29.6 db trans 1 MHz -66.59 db 144.3 MHz -89.16 db -1 3.1 MHz -33.36 db.1 5.1 1.1 15

5.1 -.812 db 54.91 MHz -.585 db trans 1 MHz -42.47 db 144.3 MHz -66.62 db -1 5.1 MHz -28.73 db.1 5.1 1.1 15 3. A New BP(band pass) filter with 3 coils BP-LP YU1LM This band pass filter realization is something new. I didn t see something similar in literature ever before. This filter offers very good performances but it is sensitive to component variation if we like to build very narrow filters. This statement is related to precise values of C3 and C4 capacitors. Filter is ideal for SMT component use especially for critical components. BAND L[uH] L2[uH] L3[uH ] C1[pF] C2[pF] C3[pF] C4[pF] C5[pF] C6[pF] 1.8MHz 12 1.8 12 47 1 68 68 1 47 3.5MHz 4.7 1 4.7 33 82 33 33 82 33 7MHz 2.2.27 2.2 18 82 39 39 82 18 1MHz 1.2.15 1.2 15 82 33 33 82 15 14MHz 1.91 1 82 33+18 27 27 33+18 82 1-14MHz.82.43.82 22 56 68 68 56 22 14-18MHz.56.22.56 15 68 82 82 68 15 18-21MHz.39.12.39 12 82 1 1 82 12+15 21-24MHz.33.1.33 1 68 82 82 68 1 24-28MHz.33 68nH.33 68 47 91 91 47 68 5MHz.15 33nH.15 47 33 56 56 33 47 5MHz*.1 6,8nH.1 33 68 27 27 68 33 Table1. Element values for BP filters with 3coils BP-LP-YU1LM (*Super-selective BP)

1.5 MHz -32.92 db 1.54 MHz -15.31 db 1.82 MHz -2.639 db 2 MHz -2.229 db 3.58 MHz -48.93 db 1.811 MHz -19.91 db 1.99 MHz -25.87 db.1 1.1 2.1 3.1 4.1 5 BP for 1.8MHz with molded chokes Qo~6 1.5 MHz -32.9 db 1.54 MHz -15.14 db 1.82 MHz -1.848 db 2 MHz -1.529 db 3.58 MHz -48.81 db 1.811 MHz.98 db 1.99 MHz -28.92 db.1 1.1 2.1 3.1 4.1 5 BP for 1.8MHz with ring core Qo~18

1.8431 MHz -28.47 db 3.583 MHz -1.532 db 4.151 MHz -1.514 db -46.52 db 1 MHz -67.33 db 4.38 MHz -22.35 db 3.54-26.1 db 1 3 5 7 9 1 BP for 3,5MHz with molded chokes Qo~6 1.843 MHz -45.4 db 3.53 MHz -33.43 db -1.577 db 1.16 MHz -36.9 Graph db 1 14..9 db 7.15 MHz -36.43 db 1 6 11 16 21 BP for 7MHz with molded chokes Qo~6

1.843 MHz -45.3 db 3.53 MHz -33.4 db -.7835 db 1.16 MHz -36.81 Graph db 1 14..7 db 7.15 MHz -34.84 db 1 6 11 16 21 BP for 7MHz with ring core Qo~18 1.843 MHz -47.81 db 3.58 MHz 1 MHz 14.2 MHz 18.6 MHz 2.21 MHz -39.75 db.18 db -1.394 db -31.4 Graph db 1-51.8 db -58.34 db 1.1 MHz -35.69 db 1 11 21 3 BP for 1.1MHz with molded chokes Qo~6

1.843 MHz -56.82 db 3.58 MHz -5.5 db -38.53 db 1 MHz -25.11 db 14.2 MHz -1.534 db 18.6 MHz -25.2 db 21. -41.6 db 27.9-61.68 db 14 MHz -46.75 db 1 11 21 3 BP for 14MHz with molded chokes Qo~6 1.843 MHz -3.12 db 3.58 MHz -22.96 db -9.588 db 1 MHz -.96 db 14.35 MHz -.8228 db 18.6 MHz -13.6 db 21. -26.29 db 28.6 MHz -45.6 db 1.1 MHz -19.32 db 14.5 MHz -25.23 db 1 11 21 3 BP for 1-14MHz with molded chokes Qo~6

3.58 MHz -31.25 db 1.843 MHz -37.73 db -21.22 db 1.8 MHz -11.5 db 14.35 MHz -.8639 db 18.28 MHz -.9726 db 21. -7.482 db 28.6 MHz -33.19 db 36.25 MHz -5.28 db 14.3 MHz -27.1 db 14.45 MHz -21.26 db 18.21 MHz -22.93 db 1 11 21 31 41 5 BP for 14-18MHz with molded chokes Qo~6-27.26 db 3.58 MHz -35.78 db 1.843 MHz -41.95 db 1.8 MHz -19.95 db 14.35 MHz -6.765 db 18.28 MHz -.992 db 21.62 MHz -.9732 Graph db1 36.21 MHz.85 db 42.1-51.2 db 18.21 MHz -25.93 db 21.1 MHz -28.7 db 21.46 MHz -25.32 db 1 11 21 31 41 5 BP for 18-21MHz with molded chokes Qo~6

-3.74 db 3.58 MHz -38.44 db 1.843 MHz -44.43 db 1.8 MHz -24.9 db 14.35 MHz -15.51 db 18.28 MHz -4.243 db 21.62 MHz -.782 db 25.54 MHz -.7821 db 36.21 MHz -26.2 db 42.1-38.65 db 21.46 MHz -28.28 db 25.16 MHz -25.28 db 1 11 21 31 41 5 BP for 21-24MHz with molded chokes Qo~6 1.8 MHz -33.35 db -38.43 db 3.58 MHz -45.68 db 1.843 MHz -51.56 db 14.35 MHz -26 db 18.28 MHz -17.42 db 21.62 MHz -7.586 db 25.16 MHz -21.18 db 25.54 MHz -.8498 db 3.51 MHz -.918 db 3.1 MHz -27.81 db 49.95 MHz -45.2 db 56.1 MHz -52.77 db 1 21 41 6 BP for 24-28MHz with molded chokes Qo~6

14.35 MHz -34.13 db 1.8 MHz -38.25 db -41.93 db 21.62 MHz -27.71 db 3.51 MHz -18.71 db 49.95 MHz -.8713 db 54.58 MHz -.9441 Graph db1 98.9 MHz -49.8 db 144.1 MHz -72.64 db 3.58 MHz -48.29 db 5.12 MHz -26.38 db 52.49 MHz -25.43 db 1.843 MHz -53.96 db 1 51 11 15 BP for 5-52MHz with molded chokes Qo~6 21.619 MHz -46.87 db 14.352 MHz -53.17 db 1.83 MHz -57.25 db 3.512 MHz -38.5 db 46.872 MHz -4.856 db 49.948 MHz 54.585 MHz -1.723 db -1.819 db 57.35 MHz -4.833 db 88.546 MHz -58.81 db 1 MHz -67.64 db.92 db 3.583 MHz -67.26 db 5.116 MHz.56 db 52.492 MHz -26.58 db 1.8431 MHz -72.93 db 1 21 41 61 81 1 BP for 5-52MHz with molded chokes Qo~6, super-selective realization is very touchy to the component variation!

4. BP with 2 coils This type of filters I published in several articles at WEB pages. Published BP filters were with 3 coils which offer much more freedom in design than with 2 coils especially if want obtain wider BP this type is very good for narrow BP type. These filters for wide bandwidth are not so good they have moderate selectivity. It is hard expect more from 2 coils only. BP filter with 2 coils BAND L1[uH] L2[uH] C1[pF] C2[pF] C3[pF] C4[pF] C5[pF] C6[pF] C7[pF] 1.8MHz 1 1 33 1 68 27 68 1 33 3.5MHz 4.7 4.7 56 39 56 24 56 39 56 7MHz 2.7 2.7 33 22 24 68 24 22 33 1MHz 1.5 1.5 22 22 22 56 22 22 22 14MHz 1 1 15 15 18 56 18 15 15 18-21MHz.68.68 47 15 1 56 1 15 47 21-24MHz.33.68.33 1 68 82 82 68 1 24-28MHz.47.47 56 91 68 56 68 1 56 28MHz.33.33 18 15 12 47 12 15 18 5MHz.22.22 68 68 56 18 56 68 68

1.4 MHz -19 db 1.56 MHz -7.151 db 1.843 MHz -1.563 db 2.12 MHz -1.881 db 3.58 MHz Graph -32.35 db1-62.85 db 1.812 MHz.38 db 2.65 MHz -21.4 db.1 2.1 4.1 6.1 7.2 BP for 1.8MHz with molded chokes Qo~6 1.843 MHz -25.9 db 3.58 MHz -1.22 db 3.822 MHz -1.234 db Graph -38.2 db1 11 MHz -55.91 db 11 MHz Schematic -55.91 db 1 3.498 MHz -21.41 db 3.84.99 db.1 5.1 1.1 11 BP for 3.5MHz with molded chokes Qo~6

1.843 MHz -37.48 db 3.58 MHz -28.43 db -1.119 db 7.355 MHz -1.231 db 1.9 MHz Graph -25.63 db1 14 MHz -42.5 db 21 MHz -58.18 db 7.2 MHz -29.96 db 7.39 MHz -25.71 db.1 5.1 1.1 15.1 2.121 BP for 7MHz with molded chokes Qo~6 3.58 MHz -36.63 db 1.843 MHz -43.7 db -22.45 db 1.8 MHz -1.349 db 14 MHz -25.84 db 14.66 MHz -28.93 db 2.21 MHz -45.38 db 24.78 MHz -54.1 db 28.43 MHz -59.58 db 1.2 MHz -23.99 db 1.42 MHz -25.58 db.1 1.1 2.1 3.131 BP for 1MHz with molded chokes Qo~6

-29.75 db 3.58 MHz -39.2 db 1.843 MHz -45.53 db 1.8 MHz -19.81 db 14 MHz -1.228 db 14.11 MHz -26.99 db 14.66 MHz 21.25 MHz -1.237 db -29.86 db 14.58 MHz -29.11 db 24.78 MHz -37.96 db 28.43 MHz -44.22 db 42 MHz.18 db.1 1.1 2.1 3.1 4.142 BP for 14MHz with molded chokes Qo~6-19.38 db 1.11 MHz -14.15 db 14 MHz -6.715 db 18.24 MHz -.7866 db 21.16 MHz -.8368 db 28 MHz -16.92 db 35.73 MHz -31.6 db 41.1-38.92 db 3.58 MHz -26.53 db 1.816 MHz -32.5 db 18.4 MHz -19.74 db 18.16 MHz -21.59 db 21.45 MHz.28 db 21 MHz -29.4 db.1 1.1 2.1 3.1 4.142 BP for 18-21MHz with molded chokes Qo~6

14 MHz -9.197 db 18.24 MHz -4.683 db 21.16 MHz -2.33 db 24.8 -.5937 db BP 24-3MHz 3.3 MHz -.6137 db 5. -27.42 db 56.5 MHz -32.67 db 1.11 MHz -13.44 db -17.34 db 1.816 MHz -29.59 db 3.38 MHz -25.45 db 28.6 MHz -23.3 db 24.9 MHz 3.58 MHz -22.21 db -23.77 db.1 2.1 4.1 6 BP for 24-3MHz with molded chokes Qo~6 1.8 MHz -26.59 db 14.35 MHz -21.56 db 21.25 MHz -11.3 db 24.78 MHz 28.2 MHz -3.865 db -.9721 db 3.51 MHz -1.321 db 49.95 MHz -36.48 db 56.18 MHz -42.7 db -3.59 db 3.58 MHz -37.12 db 28. -29.14 db 3.5 MHz -21.96 db 1.843 MHz -42.83 db 1 21 41 6 BP for 28-3MHz with molded chokes Qo~6

14.352 MHz -34.18 db 21.619 MHz -28.98 db 3.512 MHz -22.42 db 49.948 MHz -1.56 db 54.585 MHz -1.31 db 88.546 MHz -37.16 db 1 MHz -43.32 db 1.83 MHz -37.84 db -41.3 db 52.492 MHz.45 db 3.583 MHz -47.5 db 5.116 MHz -25.3 db 1.8431 MHz -53.14 db 1 21 41 61 81 1 BP for 5-52MHz with molded chokes Qo~6 5. BP with 2 coils the simplest solution ver1 This type BP filters I used several times it simple as possible solution for BP with minimum components but still very useful realization. These filters for wide bandwidth are not so good they have moderate selectivity. It is hard expect more selectivity from 2 coils and few capacitors only. BP with 2 coils ver1 BAND L1[uH] L2[uH] C1[pF] C2[pF] C3[pF] C4[pF] C5[pF] 1.8MHz 8.2 8.2 68 39 39 39 68 3.5MHz 5.6 5.6 33 91 12 82 33 7MHz 2.7 2.7 15 82 1 82 15 1MHz 2.2 2.2 1 39 56 39 1 14MHz 1.5 1.5 68 33 47 33 68 1-14MHz 1.2 1.5 22 47 27 1 15 14-18MHz.68.82 18 82 33 47 15 18-21MHz.47.47 12 82 47 91 12 21-24MHz.43.43 1 68 39 68 91 24-28MHz.39.39 82 47 27 47 82 28MHz.39.39 56 47 39 47 56 5MHz.18.18 39 33 22 33 39

1.2 MHz -21.15 db 1.499 MHz -8.358 db 1.8 MHz -1.767 db 2.16 MHz -2.226 db 3.58 MHz Graph -3.82 db1-55.36 db 1.812 MHz -19.91 db 2 MHz -25.34 db.2 2.2 4.2 6.2 7.2 BP for 1.8-2MHz with molded chokes Qo~6 1.2 MHz -28.25 db 1.8 MHz.6 db 3.58 MHz -1.95 db 4.1 MHz -1.6 db -28.1 db 1. -41.8 db 3.58 MHz -21.97 db 3.994 MHz -22.53 db.1 5.1 1.1 BP for 3.5-4MHz with molded chokes Qo~6

1.8 MHz -34.7 db 3.58 MHz -24.59 db -1.155 db 7.322 MHz -1.22 db 1. Graph -21.9 db1 14.1 MHz -36.53 db 2.95 MHz -5.58 db 7.64 MHz -21.84 db 7.339 MHz -27.6 db.1 5.1 1.1 15.1 2.121 BP for 7-7.3MHz with molded chokes Qo~6 1.8 MHz -36.86 db 3.58 MHz -29.43 db 7.18 MHz -14.6 db 1. -1.53 db 14.1 MHz -18.1 db 2.28 MHz -35.68 db 3.62 MHz -49.75 db 1.1 MHz -22.15 db.1 1.1 2.1 3.131

BP for 1MHz with molded chokes Qo~6 7.18 MHz -25.63 db 3.58 MHz -35.34 db 1. -15.53 db 14.1 MHz 14.46 MHz -.969 db -.9582 db 21.9 MHz -24.1 db 28.4 MHz -37.2 db 42 MHz -51.1 db 1.8 MHz -41.94 db 14 MHz -28.7 db 14.46 MHz -28.24 db.1 1.1 2.1 3.1 4.142 BP for 14-14.5MHz with molded chokes Qo~6 7.18 MHz -7.519 db 3.58 MHz -18.23 db 1. -.7561 db 14.46 MHz -.646 db 21.9 MHz Graph -15.51 db1 28.4 MHz -26.81 db 42 MHz.22 db 1.8 MHz -25.9 db 1.14 MHz -15.16 db 14.34 MHz -21.25 db 13.95 MHz -24.2 db.1 1.1 2.1 3.1 4.142 BP for 1-14.5MHz with molded chokes Qo~6

7.18 MHz -12.93 db 3.58 MHz -21.65 db 1.8 MHz -28.6 db 1. -5.744 db 13.95 MHz -19.43 db 14.34 MHz -19.8 db 14.46 MHz -.5557 db 18.2 MHz 21.9 MHz -.6152 db -4.382 db 18.1.62 db 28.4 MHz -18.91 db 36.13 MHz -29.5 db.1 2.1 4.1 54 BP for 14-18.5MHz with molded chokes Qo~6 7.18 MHz.72 db 3.58 MHz -28.39 db 1.8 MHz -34.57 db 1. -14.97 db 14.46 MHz -5.537 db 18.2 MHz -.6741 db 21.66 MHz -.7556 db 28.4 MHz -12.88 db 36.13 MHz -26.13 db 42.16 MHz -32.87 db 18.1-24.85 db 21.48 MHz -19.27 db.1 2.1 4.1 54 BP for 18-21.5MHz with molded chokes Qo~6c

7.18 MHz -23.46 db 3.58 MHz -3.7 db 1.8 MHz -36.77 db 1. -18.45 db 14.46 MHz -1.77 db 18.2 MHz -3.294 db 21.48 MHz -19.87 db 21.66 MHz -.5825 db 25.5 MHz -.7611 db 25.28 MHz.15 db 28.4 MHz -3.826 db 36.13 MHz -19.24 db 5.3 MHz -34.6 db.1 2.1 4.1 54 BP for 21-25MHz with molded chokes Qo~6 14.458 MHz -13.59 db 1.69 MHz -19.6 db 7.18 MHz -23.99 db 3.583 MHz -3.85 db 1.82 MHz -36.84 db 21.1 MHz -3.213 db 24.962 MHz.81 db 25.154 MHz -.4676 db 3.232 MHz -.4958 db 3.22 MHz -25.69 db 5.29 MHz Graph -24.37 db 1 56.19 MHz -29.36 db 74.898 MHz.65 db 83.979 MHz -44.97 db.1 2.1 4.1 6.1 8.1 1 BP for 24-3MHz with molded chokes Qo~6

14.458 MHz -21.23 db 1.69 MHz -27.7 db 7.18 MHz -31.37 db 3.583 MHz -38.17 db 1.82 MHz -44.15 db 21.64 MHz -1.27 db 28.6 -.5714 db 28.34 MHz -28.88 db 3.232 MHz -.6277 db 3.22 MHz -31.5 db 5.29 MHz -29.5 Graph db1 56.19 MHz -34.1 db 74.898 MHz -45.24 db 83.979 MHz -49.44 db.1 2.1 4.1 6.1 8.1 1 BP for 28-3MHz with molded chokes Qo~6 14.46 MHz -27.11 db 1. -3.94 db 7.18 MHz -34.4 db 3.58 MHz.65 db 1.8 MHz -46.5 db 21.6 MHz -22.23 db 3.2 MHz -.211 db 3.23 MHz -15.34 db 5.3 MHz -.643 db 49.9-28.62 db 53.95 MHz -.6492 db 54.6-25.3 db 11.4 MHz -32.14 db 144.5 MHz -46.42 db.1 5.1 1.1 15 BP for 5-54MHz with molded chokes Qo~6

5. BP with 2 coils the simplest solution ver2 This type BP filters I used several times it is simple as possible solution for BP with minimum components but still very useful realization. This solution is similar to BP ver1 original idea for design going from 2m LP-BP from DJ8ES. These filters for wide bandwidth are not so good they have moderate selectivity. It is hard expect more selectivity from 2 coils and few capacitors only. BP filter with 2 coils ver2 BAND L1[uH] L2[uH] C1[pF] C2[pF] C3[pF] C4[pF] C5[pF] 1.8MHz 1 1 15 68 33 68 15 3.5MHz 5.6 5.6 1 33 91 33 1 7MHz 2.7 2.7 56 18 47 18 56 1MHz 2.7 2.7 24 82 22 82 24 14MHz 1.5 1.5 24 82 22 82 24 14MHz ver1 1.5 1.5 27 82 18 82 27 18-21MHz 1 1 1 56 33 56 1 24-28MHz.68.68 82 47 27 43 82 5MHz.43.43 82 22 4.7 22 33+39

1.4 MHz -11.49 db 1.56 MHz -2.962 db 1.84 MHz -1.283 db 2. -1.48 db 3.58 MHz -34.5 Graph db 1-67.33 db 1.811 MHz -24.12 db 2.6 MHz -24.24 db.1 2.1 4.1 6.1 7.2 BP for 1.8MHz with molded chokes Qo~6 1.56 MHz.95 db 2. -17.29 db 3.58 MHz 3.89 MHz 1.48 MHz -1.174 db -1.56 db Graph -42.86 1 db -63.23 db 3.542 MHz -22.72 db 3.83 MHz -23.6 db.1 5.1 1.1.5 BP for 3.5MHz with molded chokes Qo~6

1.789 MHz -25.83 db 3.89 MHz -18.36 db -.9818 db 7.35 -.9664 db 1.48 MHz -27.26 db 14.1 MHz -45.38 db 2.98 MHz -65.72 db 7.2 MHz -24.24 db 7.329 MHz -21.3 db.1 5.1 1.1 15.1 2.121 BP for 7MHz with molded chokes Qo~6 1.789 MHz -31.86 db 3.89 MHz -24.8 db -13.7 db 1.12 MHz -.8286 db 14.1 MHz -18.76 db 2.98 MHz -43.12 db 3 MHz.29 db 1.14 MHz -3.74 db.1 1.1 2.1 3 BP for 1MHz with molded chokes Qo~6

3.52 MHz -26.19 db 1.789 MHz -32.14 db -18.9 db 1.12 MHz -11.51 db 14.1 MHz -.9248 db 14.48 MHz -.929 db 21.9 MHz -26.9 db 28.5 MHz -44.9 db 41.98 MHz -64.12 db 14.3 MHz -3.66 db 14.56 MHz -31.67 db.1 1.1 2.1 3.1 4.142 BP for 14MHz with molded chokes Qo~6 3.52 MHz -28.11 db 1.789 MHz -33.9 db -21.28 db 1.12 MHz -14.27 db 14.1 MHz -1.131 db 14.48 MHz -1.52 db 21.9 MHz -29.41 db 28.5 MHz -46.93 db 41.98 MHz -67.16 db 14.3 MHz -21.97 db 14.56 MHz -29.5 db.1 1.1 2.1 3.1 4.142 BP for 14MHz with molded chokes Qo~6 ver1

-15.25 db 3.52 MHz -22.45 db 1.789 MHz -28.55 db 1.12 MHz -1.1 db 14.1 MHz -3.696 db 18.8 MHz -26.67 db 18.4 MHz -.549 db 21.58 MHz -.6196 db 21.52 MHz -24.8 db 28.5 MHz -12.4 db 36.9 MHz -27.12 db 42.6 MHz -34.86 db 63 MHz -53.58 db.1 2.1 4.1 6.1 63 BP for 18-21MHz with molded chokes Qo~6 1.12 MHz -13.91 db -17.9 db 3.52 MHz -24.4 db 14.1 MHz -9.486 db 21.58 MHz -1.647 db 24.91 MHz -24.74 db 24.85 MHz -.618 db 3.3 MHz -.821 db 29.9 MHz -19.6 db 28.4 MHz -21.16 db 5.8 MHz -29.25 db 56.2-34.51 db 74.93 MHz -48.25 db 85.73 MHz -54.42 db 1.789 MHz -3.35 db.1 3.1 6.1 9 BP for 24-3MHz with molded chokes Qo~6

14.1 MHz -27.81 db 1.12 MHz -3.63 db 21.43 MHz -23.82 db 3.3 MHz -19.34 db 5.8 MHz -1.6 db 53.9 MHz 1 MHz -1.128 db -47.26 db 144.1 MHz -65.75 db -33.79 db 5.3 MHz -22.92 db 53.4 MHz -21.55 db 3.52 MHz -39.76 db 1.789 MHz -45.58 db.1 5.1 1.1 15 BP for 5-52MHz with molded chokes Qo~6 August 28, rewritten September 29 VY 73/72 and GL in homebrew Tasa YU1LM/QRP tasayu1lm@gmail.com References: 1. www.yu1lm.qrpradio.com 2. www.genesisradio.com.au 2. http://www.linear.com/designtools/software 4. M.Martin DJ7VY :A New Type of Preamplifier for 145 MHz and 435 MHz Receivers/UKW berichte 1/1978 5. www.dl5swb.de 6. Ed Wetherhold W3NQN Clean Your Signal with Band-Pass Filter part1 ), QST May 1998(pages 44-48), 7. Ed Wetherhold W3NQN Clean Your Signal with Band-Pass Filter part1 ), QST June 1998(pages 3-42), 8. http://www.bavarian-contest-club.de/projects/bandpassfilter/1w-bp.pdf 9. http://www.atceramics.com/ 1. Lew Gordon K4VX-Band-Pass Filters for HF transceivers, QST September 1988 (pages 17-23)