Sunday, December 6, 2015

DIY 137 MHz WX sat BP filter



Here is the simple band pass filter designed for the central frequency 137 MHz in order to filter the APT weather satellites reception and protect the receiver front-end from the strong signals nearby the central frequency. The biggest problems are coming from the close WBFM radio transmitters located on the 88-108 MHz. They can be successfully attenuated using the notch filter but still the rest of the possible „blockers“ may create a lot of problems in reception. The bandpass filter is the optimum solution where most of the problems should be solved. The broadcast TV towers, GSM/cell towers, Wi-Fi signals, radars are kept well bellow 35db. Even the aircraft AM transmissions are attenuated in a descent manner but not so effectively as other mentioned signals. The pass-band attenuation (insertion loss) is kept under 2dB and this value directly affect the overall receiving system noise figure. This should not be a problem as the man made and surrounding noise on that band is even higher . Even your LNA should be placed after the filter if you are using one. This should protect your system from IMD products that may come also from the wide opened LNA input.


Of course, it will be nice to have a small size filter, with low insertion losses, high out of the band attenuation and low cost at the end. As usual compromises are required, even here. I decided to give a try to a DIY project characterized by the small size, low cost, simple to design and fairly descent filter shape / performance. Small Butterworth bandpass filter can do the job. The calculations gave us a bit different part values and this should be corrected in manner to meet the standard capacitor and coils values so you can copy the design using the of the shelf parts. At the same time I try not to spoil the nice filter design. Here is the scheme using the standard capacitors 1pF, 4.7pF, 15pF and 68nH inductance. 


The filter is designed for the 50 ohms input/output impedance. If you plan to use the wire wound SMD coils than this will end as the no tune project. All you can do is test the filter and hope for the best, that your pass-band is really working on 137MHz  as calculated. If you make the coils by your self using the speaker wire, then you will be able to tune a bit the filter to the desired frequency. Using the one of the many on line inductance calculator make the 68nH air coil where you will have a possibility to stretch it in order to obtain the required pass-band. The tuning can be done using even the simple noise generator and the SDR dongle itself. You should reach the values where the WBFM is at least 35dB down at the end of the band (108MHz) and 50dB at the beginning of the band (88MHz). If this is not enough, you can combine the FM notch filter in series with the proposed BPF. Such a setup should result of 60dB plus attenuation of the WBFM signals which should be more than enough for the majority of RTL dongle users. Attenuation above 137 MHz is 35-40dB up to 2 GHz. Shielding the filter is always good approach but this is pain in the ass for the most of the builders. Yes, the filter will work even without the shielding using just the input / output connectors but the attenuation of the unwanted signal may suffer because of that. The strong signal may penetrate through the unshielded filter structure. Advice – use the shield for the best performance. That's it, check the video and everything should be clear, even on your spectrum :-)


69 comments:

  1. How much is the 137 MHz BPF please ?
    Thanks
    PLs : reply to iw2fvo@yahoo.com.
    Ambro

    ReplyDelete
  2. How much is the 137 MHz BPF please ?
    Thanks
    PLs : reply to iw2fvo@yahoo.com.
    Ambro

    ReplyDelete
  3. for two LNA with connector cost? I can pay with PayPal?
    plase reply to iw1cbg@cota.cc
    Thank you

    ReplyDelete
  4. This comment has been removed by the author.

    ReplyDelete
  5. What is the cost of 137mhz BP filter with 2 sma connectors? Also do you have a LNA I can use in conjunction with the filter for 137MHZ?

    ReplyDelete
  6. ordered the parts today for delivery tomorrow will let you know how it goes. Anyone asking about prices.. well i just speant 5 euros on parts and that builds the above 137mhz BP filer, an L-Band BP filter, with 3 way (137, l-band, bypass)switch, 2x female sma pcb mounted, and a bunch of spares cause the capacitors are so cheap i bought 10 of each value. most expensive part is the inductors at 1 euro each. Only comment i would make, tiny value cap especially the 4.7pF are hard to find in stock, im in bulgaria and i spent 3 days to find a company without a 2 week import delay on them including europes bigger suppliers like mouser so be prepared to wait!

    ReplyDelete
  7. This comment has been removed by the author.

    ReplyDelete
  8. Built the filer, so the supplier screwed up the order with 2 items MH not nH inductors and etch board instead of a strip, so after a few hours frustration i decided to make good with what i had. never etched before but i had a lil HCL lying around, a trip to the pharmacy for some 40% H2O2, spoon of table salt and i had what i guessed to be a good etching fluid, green fumes, thich thick green fumes and fizzing, 20 mins later the bubbles started to clear and i could see 90% success, a lil hcl injected over the unreacted parts and 5 mins later i had a board, washed it and soaked in baking soda solution and i had a nice board, a length of 1mm diam copper wire and 5 mins later i had 2 inductors, 5 miles from an airport i had a -15db signal with zero gain before on 126.660, now i need 15db gain to see it, waiting for morning noaa and m2 to see if we killed the pagers and airport likes in lrpt.wideband without tuning a nice hump from 132-143mhz, fantastic job on with broadcast fm, it's 20yrs since i touched a circuit board so i can say nice easy novice project!

    ReplyDelete
  9. I have a 36ft mast with a 5 element Yagi bolted to the top where the rotator is, running 600w. Now my interest includeds satellite tracking. Could I bolt a Turnstile with LNA attached and still run 600w. Or will there be some sort of explosion!! or I could run the coax 10 meters to under the house where I could attach it to LNA (water-proof to) then another 5 meters to the receiver inside. Are either of these two options plausible.??

    ReplyDelete
  10. Hello

    How much is the 137 MHz BPF please ?
    Thanks

    Reply to: domi93mc@gmail.com

    ReplyDelete

  11. บ้านโมเดิร์น ขนาดเล็กถึงขั้นกลาง ใช้พื้นที่ก่อสร้างไม่มากแล้วก็ปลูกภายในที่ดินที่หน้าไม่กว้างมากได้ โดยปรับลดส่วนพื้นที่ซึ่งไม่จำเป็นออก
    แล้วก็กระทำการยกระดับบางส่วนเพื่อใช้พื้นที่ได้อย่างคุ้มมากขึ้นเรื่อยๆ จึงทำให้ได้เป็นแบบบ้านขนาด 3 ห้องนอน 2 ห้องอาบน้ำ
    แล้วก็มีที่จอดรถถึง 2 คัน ห้องเก็บของ ส่วนล้างขนาดใหญ่ แล้วก็ห้องทำงานในตัวบ้าน Treetep.com

    ร้านกาแฟ
    ร้านอาหาร
    งานราชการ
    เครื่องชงกาแฟสด
    บ้านโมเดิร์น
    เครื่องวัดความดัน
    หอพัก

    ReplyDelete
  12. ทำไมถึงเทรด Forex กับโบรกเกอร์ Infinox

    ตลาด Forex เป็นตลาดการเงินที่ใหญ่ที่สุดในโลก สามารถทำการซื้อขายได้ทั้งขาขึ้นและขาลงตลอด24ชั่วโมง โอกาสในการซื้อขายยิ่งมาก โอกาสในการทำกำไรก็ยิ่งมาก

    forex
    ฟอเร็กซ์
    ระบบเทรด forex
    วิเคราะห์ทอง
    ราคาน้ํามันพรุ่งนี้

    ReplyDelete
  13. Yes, it is an educational article. Thank you for the good message. I also have a good article.
    autoslotxo

    ReplyDelete
  14. The ultimate article. Thank you for writing a good article to read.
    Sa gaming สมัคร

    ReplyDelete
  15. เล่นง่าย เกมสล็อตดีๆ joker ฟรีเครดิต แจกโบนัส slot online
    https://www.slotxd.com/jokergaming123

    ReplyDelete
  16. Hello... I built that Filter, but it don't work. May I made a mistake. I have a question: C2 and L1 (C4 and L2) are they parallel or in a row? The circuit is clear, but at the end of that video it seems to me, that C2 and L1 (also C4 and L2) are in a row?? What is correct?
    73, de Peter DL4ABB

    ReplyDelete
  17. เว็บไซด์เกมออนไลน์มหาสนุก pgslot โบนัส100 เล่นง่ายได้จริงไม่มีโกง เกมสล็อตอออนไลน์ เครดิตฟรี
    https://www.slotv9.com/pgslot

    ReplyDelete
  18. He construido su filtro y funciona segun lo esperado, probablemente utilizaré su diseño esta vez con condensadores variables para modificar el rango de frecuencias hacia 145 mhz. En general muy satisfecho. Muchas gracias!

    ReplyDelete
  19. He construido su filtro y funciona segun lo esperado, probablemente utilizaré su diseño esta vez con condensadores variables para modificar el rango de frecuencias hacia 145 mhz. En general muy satisfecho. Muchas gracias!

    ReplyDelete
  20. Great web site. A lot of useful information here. I’m sending it to several friends ans also sharing in delicious. And obviously, thanks in your effort! 야설

    Also visit my web site;
    야설

    ReplyDelete
  21. Admiring the time and energy you put into your blog and in depth information you offer. It's good to come across a blog every once in a while that isn't the same outdated rehashed material. Fantastic read! I've bookmarked your site 일본야동
    Also visit my web site 일본야동

    ReplyDelete
  22. This blog is very informative the stuff you provide I really enjoyed reading 국산야동
    Also visit my web site 국산야동

    ReplyDelete
  23. I would like to thank you for the efforts you have made in writing this article. I am hoping the same best work from you in the future as well. 일본야동
    Also visit my web site 일본야동

    ReplyDelete
  24. I have read your blog it is very helpful for me. I want to say thanks to you. I have bookmark your site for future updates.
    야설
    Also visit my web site 야설

    ReplyDelete
  25. Nice. Thank you for providing detailed information. I was looking for a band pass filter a few months ago and searched in multiple places. However, the cost is expensive in a few of nearby locations, So I started looking for the best website in online for band pass filters. Finally, I found the website anatech electronics as the best one. I got all the products at the best price. I ordered all of my required band pass filters from Anatech Electronics, as well as given a request for designing a custom band pass filter. Finally got the best products from them. Even if anyone looking for a band pass filter. You can reach out them to get the quality band pass filter.

    ReplyDelete
  26. เราได้รวบรวมเกมสล็อตแตกง่าย
    ของทุกค่ายดังใว้ให้คุณได้ร่วมสนุกมากกว่า 3,000 เกมที่นี่ที่เดียวสล็อตเว็บตรง
    มั่นคง ปลอดภัย ฝากง่าย ถอนใว ไม่มีขั้นต่ำ บริการดีตลอด 24 ช.มที่ Luckywin98

    ReplyDelete
  27. Luckywin98เว็บสล็อต
    ที่มีผู้ใช้งานมากกว่า 150,000 คน การันตีด้วยการเปิดให้บริการมาอย่างยาวนานในไทย

    ReplyDelete
  28. สมัครสล็อต
    ฟรีไม่มีค่าใช้จ่ายพร้อมรับโปรโมชั่นและสิทธิพิเศษมากมาย สล็อต เล่นฟรี
    การันตีความมั่นคง ระดับประเทศที่ Luckywin98

    ReplyDelete
  29. I really like this post it was excellent and integrating post. I must say i enjoy to reading this article thanks a lot for sharing this article and continue to good work. 파워볼게임

    ReplyDelete
  30. I am very happy with the content of your article it is very beneficial and I wait for the next article to update the information again. 카지노

    ReplyDelete
  31. หาก “กำไร” คือหัวใจของการทำบริษัท แล้ว “ทุน” ก็ถือเป็นเส้นเลือดใหญ่ที่คอยหล่อเลี้ยงบริษัทก็คงไม่ผิดนัก ซึ่ง “ทุน”
    ในที่นี่หมายถึง ทุนจดทะเบียนบริษัท หรือเงินที่ผู้ก่อตั้งบริษัททั้งหมดตกลงกันว่าจะใช้เงินลงทุนเท่าไรในการลงทุนก้อนแรก
    เพื่อเริ่มดำเนินกิจการ รวมถึงต้องแจ้งข้อมูลไว้ตอนจดทะเบียนบริษัท โดยตัวเลขของทุนจดทะเบียนดังกล่าวก็จะมีปรากฏอยู่บนหนังสือรับรองบริษัทของเราด้วย
    นั่นย่อมแสดงให้เห็นว่า บริษัทมีความน่าเชื่อถือมากน้อยเพียงใด ยิ่งทุนจดทะเบียนสูงความน่าเชื่อถือก็สูงตามไปด้วย

    ภาษีเงินได้นิติบุคคล
    งบกระแสเงินสด
    งบกำไรขาดทุนเบ็ดเสร็จ
    ภพ 09
    ภาษีหัก ณ ที่จ่าย คือ
    ทุนจดทะเบียน คือ
    เปิดบริษัท

    ReplyDelete
  32. Pretty nice post. I just stumbled upon your weblog and wished to say that I have truly enjoyed surfing around your blog posts. In any case I will be subscribing to your rss feed and I hope you write again soon 먹튀신고

    ReplyDelete
  33. First of all, thank you for your post. 바카라사이트 Your posts are neatly organized with the information I want, so there are plenty of resources to reference. I bookmark this site and will find your posts frequently in the future. Thanks again ^^

    ReplyDelete
  34. I've been looking for photos and articles on this topic over the past few days due to a school assignment, 우리카지노 and I'm really happy to find a post with the material I was looking for! I bookmark and will come often! Thanks :D


    ReplyDelete
  35. Your information was very useful to me. That's exactly what I've been looking for 샌즈카지노!

    ReplyDelete
  36. Your explanation is organized very easy to understand!!! I understood at once. Could you please post about 우리카지노?? Please!!


    ReplyDelete
  37. The assignment submission period was over and I was nervous, 우리카지노 and I am very happy to see your post just in time and it was a great help. Thank you ! Leave your blog address below. Please visit me anytime.

    ReplyDelete
  38. ลงทุนน้อยก็รวยได้ แถมยังทำกำไรได้รวดเร็วทันใจใน PGสล็อต เล่นเกมสล็อตกับเราวันนี้ พร้อมรับโบนัสและโปรโมชั่นดี ๆ กดได้ที่ PGSLOT.TO ผู้เล่นสามารถเลือกเล่นเกมสล็อตออนไลน์กับเราได้มากมาย และเลือกเล่นได้ตามความชื่นชอบทันที แถมยังลุ้นรับเครดิตฟรีได้นานและถี่ตามที่ต้องการ ฝากถอนง่าย ผ่านแอพพลิเคชั่นสุดทันสมัย ไม่ต้องรอ !

    ReplyDelete
  39. เปลี่ยนเงินทุนหลักหน่วยให้เป็นหลักหมื่นได้ง่าย AMBBET เว็บไซต์สล็อตออนไลน์ ที่ให้บริการ superslot สล็อตครบทุกค่าย ครบทุกเเบรนด์ ครบทุกเกม สล็อตเครดิตฟรี 100% เอาใจนักเดิมพันงบนน้อยกับโปรเด็ด ฝาก 1 รับ 100 ทุนน้อยก็เล่นได้ โปรโมชั่นสุดพรีเมียมดีๆ เเบบนี้ไม่ควรพลาด เล่นง่าย จ่ายเต็ม ถอนได้ไม่อั้น ถอนฟรี บริการฟรี 24 ชั่วโมง ทำเงินพิชิตเเจ๊คพอตก้อนโตได้ง่ายๆ ผ่านหน้าจอโทรศัพท์มือถือ รองรับทั้งระบบ iOS เเละ Android

    ReplyDelete
  40. There can be different reasons on why you might need essay writing help online. It depends on individual preferences and situations. Sometimes students need expert assistance because they fail to cope with the stress of too many academic tasks. In some other situations, students don’t have adequate knowledge about the assigned topic.
    Essay writing assignment helper is also required in instances where students don’t have a piece of in-depth knowledge about essay writing patterns, structure and other basics. You can see whether you are facing any of these issues or not. Just in case you are struggling to write an essay feel free to reach experts.

    ReplyDelete
  41. When did you start writing articles related to ? To write a post by reinterpreting the 메리트카지노 I used to know is amazing. I want to talk more closely about , can you give me a message?

    ReplyDelete
  42. Only the most talented authors are selected and hired. With our essay writing service, you can rest assured that your assignment help online will be completed by a top Assignment Helper with a wealth of experience. If you are having trouble meeting all of your deadlines due to an increasing number of projects, our professionals are always available to help you with your essays.

    ReplyDelete
  43. buy dissertation visible learner or simply want to change up however you define your essays, mind maps are often a game-changer. they create developing ideas for your essay and organize them super simple. order dissertation online used a mind map for essay writing before, don’t worry—we break down everything you would like to understand to induce started within the steps below. We would like to help you in the field of order dissertations online.

    ReplyDelete
  44. Instant assignment help in Australia without any compromise in the quality. It has been observed that students often find themselves in an urgent need for academic assignments. Instant assignment help is because of various factors such as procrastination, short deadlines, or due to urgent work. To help students in such situations, our most efficient academic experts have taken the charge.

    ReplyDelete
  45. I was amazed to see the long-lasting string of valued content pieces. Hence, it would be great to keep it up. To leverage mutual communication, you should connect with the assignment help online. e team for in-depth learning.

    ReplyDelete
  46. You must be wondering how can one rely on the online platform. Your concern for the digital platform is right and it’s true when you invest your money online you should thoroughly check the website so that they cannot make you fool by stealing your money. my assignment help Please always be specific when you choose the service for you. Following are some advantages that one should always get when they buy the writing service.

    ReplyDelete
  47. I came to this site with the introduction of a friend around me and I was very impressed when I found your writing. I'll come back often after bookmarking! 먹튀검증

    ReplyDelete
  48. If you are battling to structure your paper for Business Law Assignment, you will find the definite answer at our Business Law Assignment Help platform. Great Assignment Helper provides you the 360degree support required to develop premium quality assignments worthy of fetching excellent grades. Our experts are very qualified and highly experienced dedicated academicians renowned for their command over the subject. Despite being the best service provider out there, our prices are always reasonably cheap and affordable.

    ReplyDelete
  49. Wow! Great quality content. Are you also looking for Finance assignment help Canada because you do not know how to make top-quality projects? Take the academic writing assistance from professional writers and get the top-class projects written in the least amount of time.

    ReplyDelete
  50. Playing online has another feature that doesn't have to travel to play in the real place. In addition, the web has a live broadcast while playing for real. Makes it possible to be able to watch their own and others' play as well. The live betting is available throughout the day. Online gambling is safe. And get more rewards than normal playing online slots in playing games สล็อต

    PG

    ReplyDelete
  51. Your article has answered the question I was wondering about! I would like to write a thesis on this subject, but I would like you to give your opinion once :D 꽁머니

    ReplyDelete
  52. I think this is one of the most significant information for me.
    And i’m glad reading your article.
    wordpress
    blogspot
    youtube
    ភ្នាល់បាល់បក

    ReplyDelete
  53. Decent data, profitable and phenomenal outline, as offer well done with smart thoughts and ideas, bunches of extraordinary data and motivation, both of which I require, on account of offer such an accommodating data here 토토사이트

    ReplyDelete
  54. If you have no time Use Assignment Help in Queensland Services for assistance. Writing assignments is difficult, and mostly people find it exhausting. Connect with our Online Assignment Help

    ReplyDelete
  55. We construct bespoke compositions only and they are always counterfeit free which consistently meet the faculty requirements. Our help with homework online has consistently earned excellent academic grades for understudies.

    ReplyDelete
  56. superslot Free credit 50 ซุปเปอร์สล็อต Which slots game breaks the most ทดลองเล่นสล็อต free every game. ทางเข้า superslot Online slots latest update Play all the time, give out hard money, give out often, big bonuses.

    ReplyDelete
  57. superslot Free credit 50 Online slots are the most advanced auto systems. ทดลองเล่นสล็อต free every game ทางเข้า superslot Make the play of every player It works well and doesn't cause any problems.

    ReplyDelete
  58. We can provide you with the best and most remarkable task papers to amaze your professors. When it comes to securing excellent grades, students choose us first. Our expert Assignment Helper provides understudies with the best paper solutions, resulting in top scores on the scorecard.

    ReplyDelete
  59. pg slot, the best of the online world, the hottest free slots website, unlimited deposit-withdrawal, whether it's a promotion or free credit เกมทดลองเล่นฟรี You can message us at the entrance to pg slot. We have admins to serve you 24 hours a day. Quick reply, don't let players wait for a long time. And for any player who has problems with various jams, whether it is not depositing money can't withdraw money Ask us now.

    ReplyDelete
  60. What are the "P" components at either end ? Just a port ? And the circles with sine wave ? Just signal indications ? What type of caps were used ? Thanks for sharing. Really want to build this. Some one else already did with variable coils.

    ReplyDelete
  61. ฝาก ถอน ตลอด 24 ชั่วโมง โปรโมชั่น 20รับ100 ทํา 200 ถอนได้ไม่อั้น ที่ สล็อตเว็บตรง888 โบนัสแตกแจกไม่อั้น

    ReplyDelete
  62. เกมสล็อตที่กำลังโด่งดังที่สุดในตอนนี้คงหนีไม่พ้นเว็บสลอดพีจีที่กำลังเป็นกระแสและทุกคนทั่วโลกต่างเล่นกันเลยตอนนี้สมัครเลยวันนี้พร้อมรับโปรโมชั่นมากมายที่รอคุณอยู่อีกเพียบ joker slot เว็บตรง

    ReplyDelete