Popular Posts

Saturday, October 27, 2012

How to select the operating mode of TP-LINK wireless multiple modes devices?


Suitable for: TL-MR3020, TL-MR3040, TL-WA5110G, TL-WA5210G, TL-WA7510N, TL-WR543G, TL-WR700N, TL-WR702N, TL-WR743ND
Some TP-LINK devices have multiple operating modes, such as AP/ Wireless Router/ Repeater/ Bridge/ Client/ AP Client Router. You may be confused about which mode I should use. Here is an article explains how each mode works to help you make a decision.
 
1.    AP Mode(for hotel Internet extension)
AP mode is more used to transfer wired connection into wireless. It works like a switch. Usually, it is behind a router.
If you are in an office, hotel and places where only wired network is available, or LAN gaming party, small meeting and other situations where a temporary wireless network is needed, please use the AP Mode.
 
2.    Wireless Router Mode(for home Internet sharing)
With the router mode, it can share one wired Internet connection to several clients. At that time, there will be one WAN port. It supports multiple connection types, like Dynamic IP/Static IP/PPPoE/L2TP/PPTP.
When Internet access from DSL or cable modem is available for one user but more users need to share the Internet, please use the Router Mode.
 
3.    Repeater mode(for home Wi-Fi extension)
Repeater mode is used to extender the wireless coverage with same SSID and security.
When you have a wireless already, and there is some place can’t be covered, you can consider Repeater Mode. With Repeater mode, you will have only one SSID. At that time, your wireless clients can roam in whole place.
 
4.    Bridge Mode(for home or business networking)
Bridge mode borrows existing wireless Internet and broadcasts it using a different network name (SSID) and password. This application can create two individual networks for two groups of users sharing one Internet.
For small restaurant, bar, home, office and others where Internet service needs to be provided for guests without revealing the password of the existing network for hosts, Bridge Mode is the best choice.
 
5.    Client Mode(for home gaming console)
With client mode, it can connect to a wired device and works as a wireless adapter to receive wireless signal from your wireless network.
For a Smart TV, Media Player, or game console with an Ethernet port. Use the Client Mode to make your devices Wi-Fi enabled, granting them access to your wireless network.
 
6.    AP Client Router Mode(for WISP user Internet sharing)
With AP client router mode, it can connect to a wireless network and share the connection to its clients. The wireless is its WAN side. It can also support Dynamic IP/Static IP/PPPoE/L2TP/PPTP.
When the wireless station limits the number of clients or asks username/password to connect, AP Client Router Mode is what you need.

Mudiak Arau - Guitar Strumming

Teratai - Sweet Charity (Guitar Cover)

Thursday, October 25, 2012

9M2PJU's HF Portable Station At Bukit Keluang

1941 Morse Code Class

Kuala Lumpur Remote Control Cars

9M2PJU CW Dxing on 20m band

9M2AR And 9M2RB On 7.043 MHz

Bersiar-siar Di 40m Band

Patah Seribu - Sheila Hamzah (Guitar Plucking And Strumming)

Father And Son - Yusuf Islam (Formerly Known As Cat Steven)

Green Green Grass Of Home - Tom Jones (Guitar Strums)

A Mi Manera (Spanish Version Of My Way - Frank Sinatra) Instrumental Gui...

Aku Suka Dia - Ainan Tasneem (Original) Video Respond

Stay - Estrella (Guitar)

Anak Kampung - Jimmy Palikat (Guitar Cover) Video Respond

Tasha Manshahar - Be Mine (Original) Video Respond

Sentuhan Listrik Mu M. Nasir Guitar Cover

9M2AR And 9M2ZN High Speed CW QSO

9M2PJU 500mW QRP CW QSO WITH 9M2AR USING YAESU FT817ND

9M2AR Morse Code Video

Magnetic Loop Antenna Test

DU9XO CQ DX On JRC NRD 545 DSP Receiver

9M2PJU QRP Operation With Yaesu FT817ND

Monday, October 22, 2012

9M4CJB Operated By 9W2JJF CW QSO

Pada malam 21 Oktober 2012, saya telah dikejutkan dengan satu panggilan telefon dari Zaki 9M2ZAK. Beliau bertanyakan samada saya berkelapangan atau tidak, mujurlah ketika itu saya tidak sibuk seterusnya saya bertanyakan kenapa?. Cikgu Zaki 9M2ZAK mengajak saya untuk ke udara dalam mode CW atau kod Morse untuk sesi latihan kepada bakal calon CW test 2-2012 iaitu Ustaz Illiyas 9W2JJF.

Setelah mencari frekuensi yang sesuai, saya berhenti di satu frekuensi yang tiada QRM, berikutan semua segmen bagi narrow bandwidth operation di 40m band telah digunapakai secara haram oleh lanun (lanun adalah istilah kepada mereka yang beroperasi tanpa kebenaran yang sah). Kebanyakan lanun beroperasi dalam mode single side band atau pendeknya SSB. Mereka memancar (transmit) dengan jumlah kuasa pancaran yang agak tinggi (lebih dari 100 watts). Ini menyebabkan gangguan kepada operator radio amatur yang ingin bekerja dalam mode CW pada narrow bandwidth portion. Saya beroperasi di frekuensi yang bukan center operation bagi lanun-lanun tersebut. Filter dan noise reduction perlu dipasang untuk keselesaan semasa beroperasi.

Setelah beberapa transmission, saya berhenti seketika dan selepas itu saya sempat CW QSO dengan Cikgu Rahman 9M2AR di frekuensi tersebut. Beliau memaklumkan yang beliau baru balik dari makan malam. Saya memberitahu beliau akan sesi latihan untuk 9W2JJF akan disambung semula dan selepas itu Cikgu Rahman 9M2AR memberikan kami laluan.

Di bawah adalah video yang sempat dirakamkan oleh Zaki 9M2ZAK, di mana di dalam video ini menunjukkan 9W2JJF sedang ke udara dengan menggunakan callsign 9M4CJB sambil dipantau oleh 9M2ZAK.




Sifat dan kesungguhan 9W2JJF harus dipuji kerana beliau berusaha untuk mendapatkan sesuatu yang beliau inginkan. 9M2ZAK juga memainkan peranan penting dalam sesi pembelajaran kod Morse Ustaz Illiyas 9W2JJF. Sesungguhnya di mana ada kemahuan, di situ ada jalan. Hendak seribu daya, tak nak seribu dalih. Semoga berjaya menempuhi CW test 2-2012 yang akan tiba kepada 9W2JJF. Jumpa lagi di udara!

73 de 9M2PJU


Saturday, October 20, 2012

9M2PJU CW QSO With Ali A71CV


Keadaan 40m band agak bising ketika ini, tetapi saya berjaya berhubung dengan Ali dari Qatar dengan report 579.

Bersiar-siar di 40m Band

Mesej Tersembunyi (Morse Code) Dalam Lagu

Di Colombia, polis dan askar yang diculik dan ditahan oleh gerila FARC selama 12 tahun lebih hanya dibenarkan untuk mendengar berita dan juga muzik tertentu di radio. Pihak DDB Colombia dengan kerjasama tentera Colombia telah mencipta satu lagu yang mengandungi mesej tersembunyi (hidden message). Rentak yang sebenarnya pada chorus lagu itu adalah kod MORSE, memberitahu tentang berapa orang mangsa tahanan telah diselamatkan dan mereka juga akan diselamatkan nanti. Ini penting untuk mengembalikan moral tahanan yang telah lama ditahan pihak gerila.


"The Code" - Lagu ini telah ke udara selama 2 bulan lebih di 100 stesen radio berlainan merentasi Colombia. Bagaimanapun, hanya orang tertentu sahaja yang memahami mesej tersembunyi itu dan mereka adalah 16 mangsa tahanan gerila FARC. Mereka telah menyebarkan mesej tersembunyi itu kepada tahanan lain (19 liberadossiguen ustedesanimo) yang bermaksud "19 people rescued, you're next, don't lose hope"

Untuk pertama kali dalam masa sedekah, tentera Colombia berjaya menyusup masuk (mesej tersembunyi melalui radio) ke kawasan gerila FARC, memberikan semangat dan harapan kepada tahanan.



Ini adalah salah satu teknik kreatif dalam penggunaan kod Morse demi menyelamatkan NYAWA tahanan dan cerita ini akan tertulis dalam SEJARAH penggunaan kod Morse untuk renungan generasi masa hadapan. Sebagai maklumat tambahan, lagu ni menang anugerah Cannes Lions 2011 untuk kategori Gold Best use of music and/or sound design

International Morse Code Lesson

Koleksi Majalah Radio Amatur Part 1

CQ magazine June 2001

CQ magazine March 2001

CQ magazine September 2001

CQ magazine Disember 2002

CQ magazine October 2003

CQ magazine April 2001

QST magazine April 1997

CQ magazine July 2003

CQ magazine January 2001

CQ magazine April 2002

CQ magazine June 2002

CQ magazine January 2003

CQ magazine March 2003

CQ magazine January 2002

CQ magazine May 2001

CQ magazine December 2002

CQ magazine May 2003

CQ magazine August 2002

CQ magazine May 2002

CQ magazine February 2001

CQ magazine February 2003

QST magazine December 1997

CQ magazine April 2003

CQ magazine November 2003

CQ magazine June 2003

CQ magazine July 2002

CQ magazine October 2002

Noise Di High Frequency


Pada awal pagi sabtu 20 Oktober 2012, sedang saya memanggil CQ di 14.011 MHz. Misao JH2XMK menjawab panggilan saya. RST adalah 449, signalnya lemah berbanding stesen lain. Setelah bertukar signal report, saya menamatkan QSO dan menghantar 73 kepadanya.

Stesen dari Jepun selalunya ramai ke udara di frekuensi seperti 10, 15 dan 20 meter band. Ini mungkin kerana antenna yang diperlukan tidaklah sebesar antenna biasa untuk 40 atau 80 meter band. Kebanyakan operator dari Jepun tinggal di rumah flat atau rumah bertingkat, ruang untuk memasang antenna amatlah terhad. Populasi di bandar-bandar utama negara Jepun juga lebih dari bandar utama di Malaysia.

Tempat tinggal yang terhad tidak mematahkan semangat mereka untuk ke udara. Sebaliknya menjadikan mereka bijak dalam faktor pemilihan antenna dan juga operating frequency. Jika dibandingkan dari aspek pembangunan teknologi, Jepun semestinya adalah negara yang dikatakan lebih maju berbanding negara lain. Penggunaan internet yang meluas, gadjet eletronik termaju dikatakan dihasilkan di negara Jepun.

Kehidupan penduduk Jepun di negara mereka yang pesat membangun sudah menjadi satu cabaran, terutama untuk operator radio amaturnya. Broadband over powerlines sebagai contoh, menjadi satu cabaran buat mereka. Noise yang terhasil sudah tentu menjadikan mereka susah untuk beroperasi dalam mode SSB. Kebanyakkan operator radio amatur Jepun memilih untuk beroperasi dalam morse code atau mode CW. Noise boleh ditapis dengan penggunaan IF atau AF DSP dan noise reduction. Receiving bandwidth boleh disempitkan dengan CW filter.

Urban area atau built up area menghasilkan banyak noise kepada frekuensi tinggi (HF), powerlines yang membawa voltan tinggi ke rumah atau premis, sambungan yang kurang sempurna pada tiang-tiang eletrik, insulator yang bocor, lampu neon, lampu LED, peralatan eletrik yang mengeluarkan spark dan sebagainya boleh meningkatkan kadar noise frekuensi tinggi.

Hasil dari pembacaan saya pada majalah QST, artikel bertajuk "powerlines interference" menceritakan tentang punca dan sebab gangguan berlaku, bagaimana untuk mengesan sumber gangguan dan juga bagaimana untuk menghapuskan gangguan terhadap frekuensi tinggi akibat dari powerlines.











Antara peralatan yang digunakan adalah, Line noise meter.




Friday, October 19, 2012

9M2PJU CW QSO WITH HA8QZ ON 10 METER BAND


Pada petang jumaat, 19 Oktober 2012 saya berjaya bekerja dengan Lali HA8QZ di 28 MHz. Signalnya kuat diterima di Rawang.


Signals Training Video TF11 - International Morse Code (complete)

Morse Code - Principles and Basic Techniques (US Army Signal)

SEJARAH TELEGRAPHY



Now simply called "CW", radio communication by Morse code was the only way to communicate for the first decade or more of Amateur Radio. Radiotelegraphy, the proper name, descends from landline (wired) telegraphy of the 19th century, and retains some of the old culture, including a rich set of abbreviations and procedures. Morse sent by spark gap transmitter was the first wireless communication mode. These "damped waves" were very broad and inefficient for communication. They were soon replaced by "Continuous Wave" (CW) transmission, using vacuum tube oscillators that were capable of a very pure note. Today, modern Amateur Radio transceivers use solid state components and microprocessors to support a variety of communication modes including CW, voice, image and many digital data modes.

Technique Of Hand Sending For CW Operator

Antara Straight Key, Iambic Key, Bug Dan Cootie

Morse code sudah lama tertulis dalam sejarah, wujud sekitar 176 tahun yang lepas. Mode terawal dalam sejarah penggunaan eletrik sebagai penghantaran mesej melalui wayar dan juga radio tanpa wayar. Operator kod Morse telah banyak menyelamatkan nyawa mereka yang dalam kecemasan. Kapal Titanic sebagai contoh, operator radionya menghantar distress call atau panggilan kecemasan dalam kod Morse. Morse key atau CW key terdapat dalam beberapa jenis, di antaranya adalah:-


  1. Straight key - key yang biasa digunakan oleh operator radio tentera, kapal dan juga radio amatur. Key jenis ini sangat mudah, kerana hanya mempunyai 2 sambungan wayar. Bunyi dit atau dah ditentukan oleh ketukan operator. Ketukan pendek akan menjadikan bunyi dit dan ketukan yang panjang menjadikan bunyi dah.
  2. Iambic key - iambic key, eletronic key atau automatic keyer biasanya mempunyai 3 sambungan wayar dimana terdapat litar eletronic yang akan menentukan bunyi dit dan dah. Kelajuan ditentukan dalam word per minutes. Kelajuan dan nisbah dit dan dah boleh diubah pada litar eletronik yang mana selalunya terdapat dalam hampir kesemua transceiver moden. Sesuai untuk mereka yang sukakan kod morse dalam kelajuan yang tinggi (high speed telegraphy). Terdapat dalam versi dual paddle atau single lever. Begali menawarkan single lever iambic keyer yang boleh diubah kepada cootie atau sideswiper dengan hanya mengubah satu kedudukan suis.
  3. Bug - bug atau semi automatic adalah single lever key yang klasik selalu digunakan oleh operator radio. Mempunyai 2 sambungan wayar, tidak memerlukan litar eletronik sebaliknya key ini mempunyai mekanikal yang akan menentukan bunyi dit. Tetapi, untuk bunyi dah pula operator perlu menghantar secara manual.
  4. Cootie - Cootie atau sideswiper adalah satu single lever key, mempunyai 2 contact point dan 2 sambungan wayar. kiri dan kanan contact point adalah sama. Bunyi dit atau dah perlu ditentukan oleh operator.


Sila lihat video di bawah untuk melihat perbandingan di antara straight key, iambic key, bug dan juga cootie.

Straight key 


Dual Paddle Iambic Key


Single Lever Iambic Key


Bug atau Semi Automatic


Cootie atau Sideswiper


Key jenis apakah menjadi pilihan anda?


Thursday, October 18, 2012

Panggilan Kecemasan Dari R.M.S Titanic

cerita yang dibikin semula menceritakan bagaimana kehidupan operator radio kapal RMS Titanic, Jack Phillips dan Harold Bride sebelum mereka mati. Walaupun mereka telah dibebaskan dari duty oleh kapten kapal ketika Titanic hampir karam, tapi mereka setia di radio room bersama CW keyernya, menghantar panggilan kecemasan, "CQD CQD SOS SOS CQD DE MGY MGY" sehingga ke hembusan terakhir. Inilah sejarah penggunaan kod Morse.



Tribute to the RMS Titanic Radio Operator



Tribute to the RMS Titanic, callsign MGY, with emphasis on the duty of her wireless officers.
They stayed with the ship, sending distress messages, even though released from duty by Captain Smith a few minutes before she went down.

When the water came onto the bridge, and the power failed, they were swept off Titanic and into the icy sea.

Senior operator John "Jack" Philips, just 25 years old died of hypothermia, and Harold Bride aged 21 years, second operator, was eventually pulled from the sea onto an overturned lifeboat.

Despite suffering crushed feet and frostbite, he insisted on being carried to the radio room of the rescue vessel Carpathia, where he remained assisting her operator who was exhausted from working continuous distress traffic and lack of sleep.



Over the next ninety years, radio and morse code were to save countless lives at sea.

My Personal Morse Code Story - Larry W2LJ


I was not always enamored with Morse Code like I am now.  This is a personal story that began when I was about 16 years old or so.  When I was in high school, I wanted to become a Ham.  I had the fortune of having an electronics teacher, Mr. Benson, who was already a licensed Ham.  We had a club station at school; and from demonstrations of the radios, I knew I wanted to get "in" on this great hobby.  Mr. Benson tried to teach a bunch of us the Morse Code; but I wasn't getting it.  In addition to the standard printed out sheet, I went to our local Lafayette Electronics store and purchased an Ameco Code Phonograph Album (remember those?).  No matter how much I practiced, it was no use.  It was all mumbo-jumbo; and unfortunately for me, I gave up after a relatively small amount of frustration.

Fast forward four years.  I had graduated college; had a full time, but not-so-great paying job; and had some free time on my hands, now that homework days were pretty much gone forever.  The local newspaper was advertising an Amateur Radio course that was to be given by a neighboring town's Adult Continuing Education Program.  The spark had reignited and was now a bonafide blaze.  I vowed to myself that this time I would actually do it.

Eight weeks later, as a result of hard work, study and perseverance, I had passed my Novice test.  The teacher had faked us out by promising to give us a "pre-test" so we would feel more comfortable taking the actual code test.  Little did we know that the "pre-test" would negate the need for us to take the "actual test".  We all passed with flying colors!  Approximately six weeks later, I received an envelope through the mail from the FCC with the much coveted "ticket".  I was a "gen-you-ine" Ham radio operator, licensed as KA2DOH.

Still with big dreams in my head, I worked towards my General license.  Visions of sitting behind a desk, with my legs on top, leaning back in a chair, all the while clutching the magic microphone working all the juiciest DX,  filled my brain.  Code was for Novices!  I was to leave it all behind !!!  The next few months saw my code speed rise to the magic 13 WPM mark.  My General Class license study guide was my constant companion.  Six months after receiving my Novice license, I took the test before an FCC examiner and was awarded my General!  I had done it - my hand was firmly grasping the Holy Grail !!  Look out DX, here I come !!!

I rushed home to my "new" used Kenwood Twins, the T599D and R599D.  These were my gift to myself for passing the General exam.  I fired the rig(s) up and got on 20 Meters (the Big Boys band, the promised land - Heaven!).  I took that ol' Astatic D-104 in hand and listened intently for a clear frequency and began to send my voice through the aether as I called CQ.  Meanwhile, unbeknownst to me, I was playing weird LSD style dream games with the TV downstairs.  The picture was a mess, the speaker sounded like a rabid and psycho Donald Duck was trapped inside.  Welcome to RFI, Mr. KA2DOH - welcome to stark reality.  This never happened in the six months of pounding the straight key !!!  The TV never so much as whimpered while I was pounding the brass.

The next few weeks were spent trying to overcome the RFI problem.  Various solutions were tried with varying success.  But it never went away entirely.  If I was to operate during "prime time" it was going to have to be Morse Code or be relegated to family imposed "quiet hours".  It soon became apparent to me that good old CW was to be my salvation.  And you know what ?  I came to love it !!  Once I stopped railing against it; I found that I enjoyed it immensely.  I came to love the sounds, the rhythms, the "song" that Morse Code is.  Today, I operate using CW 100 percent of the time.  In fact, right now I do not even own a rig that has SSB or AM capability.  If you want to find W2LJ, he'll be in the CW portion of the band, pounding brass and loving every second of it.

Learning the Code

Before I go into this .... if any of you out there want an "On-The-Air" tutor, I will do my utmost to get on the air with you for live CW practice, if you want!  Just drop me an e-mail and I'll try to meet you on the air, at a speed you're comfortable with - propagation permitting, of course!  Again, my e-mail is w2lj@arrl.net

There are probably as many different methods for learning Morse Code as there are students trying to learn it!  From the old Boy Scout method, where you would see the letters on a chart and then learn the characters to such "newer" methods as listening to letters delivered as jazzy, upbeat techno-tunes as in the popular CD, "The Rhythm of the Code".

We've come a long way from learning the Code from LP records (Ameco Code Course), cassette tapes, and even machines designed specifically for learning the Code, such as the old Instructograph.  Today there are a plethora of freeware, and shareware computer programs which will aid in your learning process.  Before we go into them, a few words first about learning the Code.

Learn each letter as a "sound".  Do not learn the letters at such a slow speed that you can count each dit and dah.  If you do it that way, then you will hit the dreaded "plateau"!  This is what we all faced in the olden days when we learned code the old fashioned way.  We learned code characters that were sent to us at a 5 WPM rate.  (For example, the letter C was learned as dah        di        dah        dit).  Then, as Novices, when we tried to increase our speed up to 13 WPM for the General license test; we found the going got rough at about 10 WPM.  It's at that point that Code is coming at you at a rate where you can no longer count the individual dits and dahs.  At this speed you have to unlearn everything you had learned to that point; and you had to learn the sound of each letter as a whole.  It's much easier if you learn it that way to begin with; and this is called the Farnsworth Method.  Play the letters as if they are being sent at a 10 -15 WPM rate (Example - learn C as dahdidahdit) ; but increase the spacing between each letter to achieve the effect of 5 WPM.  If you go this route you will not be tempted to pull your hair out later!

All that having been said, use the program you choose wisely.  This is not an endorsement of one program over another; but one of the nice things about the G4FON program is that you can click and choose the letters you want to concentrate on.  Once you have the basic letters, numerals and punctuation down; but find yourself having trouble with the "sound alikes"; you now have a remedy.  With the G4FON program, you can click just "H" and "5"; or "B" and "6"; or "L" and "F" or "L" and "R" or whatever you might be having a problem with.  (From my examples, you can see where I had problems. Hi!)  This way you can gain the confidence you need to go further.  Please remember that learning Morse Code is not a one shot deal! Once you've learned the 5 WPM rate to pass the license requirement, it doesn't end there.  Getting on the air, you will find that conversational CW begins somewhere around 13 to 15 WPM.  At slower speeds it's kind of like two people talking at each other instead of with each other.

Practice, practice and practice!  And then practise some more.  Listen to Code whether it's software generated or on the air from W1AW or from real time QSOs.  The more you listen, the better; but you want to limit your "concentrated" learning sessions to no longer than about 15 to 20 minutes.  After that you kind of go into "sensory overload" and it becomes counter productive.  A good thing to do is to set up one of the Code practise programs to generate a sound file that you can burn to a CD so you can listen in your car while driving; or even while doing other chores around the house.  It is amazing how much you can pick up when you're just in "listening mode" with the code playing in the background.

Another little "thing" that you can do to help yourself learn code is to "tongue" it.  I know, it sounds obscene; but all this is, is sounding out dits and dahs to yourself using your mouth.  While you're driving back and forth to work, code out some of the signs you see on the road.  Training yourself to translate normal words into Morse Code is good reinforcement. (Oh boy, it's a good thing I didn't miss that ditditdit dah dadadah didadahdit sign!)  You get the idea!

The most important thing - relax, relax and relax some more.  Frustration is your worst enemy and causes more people to give up than any other reason.  You will finally "get it", just don't put too much pressure on yourself!  Learning the Morse Code and using it is one of the most enjoyable aspects of this hobby as far as I'm concerned.  Don't make it out to be such an ordeal.  If you approach the whole process with a positive outlook; you will be amazed at what you can accomplish

http://w2lj.blogspot.com/p/morse-code.html

V85AN Demonstrate His Homebrew Iambic Keyer

CQ 14.030MHz With V85AN Homebrew Paddle

Just trying Azril V85AN homebrew keyer. He made it from a saw blade, equipped with magnetic base, so i can stick it the my cooking pan and it become large and huge base expansion. HIHI.

9M2SX QSO WITH 9M2NZ ON 7130 kHz

Two amateur radio operator from West Malaysia having their conversation on 40 meter amateur radio band. 9M2SX is from Penang Island and 9M2NZ from Nilai, Negeri Sembilan.

Lanun Di 145.500 MHz

Pirates on amateur radio 2m bands. Recorded by 9W2CEH from his QTH in Bangi, Selangor, West Malaysia.

Indoor antenna operating tips


For the past few years I have been tinkering with many forms of indoor amateur radio antennas. I want to pass along these operating tips to try helping other operators in my position.
These are mainly observations on what has worked and what hasn't. Just because you can't have a full-blown station doesn't mean you can't be active on the HF bands.


Your choice of modes means a lot!

One of the biggest factors that affects your success using an indoor antenna on the HF bands is your choice of mode. While these tips are only suggestions, they have proven to be successful for me and have enhanced my stations performance.


CW Rules!

CW means more DX!
Let's face it, for any sort of weak signal work, CW is the most efficient mode available to us today! Big DX'peditions usually concentrate most of their effort in CW for that reason.
With all of the varied modes available for HF operation available, CW has always been my best mode for success. I have been a ham for almost 30 years now and have always preferred CW. New hams aren't required to learn it to get their licenses but there are some factors that make it the perfect mode to use when working with limited antennas. Remember, Morse Code is a 100% duty cycle mode so your signal will stand a better chance of being heard than if you were using phone.
This fact became apparent to me many years ago when I used to do satellite operation. Back when I had outdoor antennas I became interested in operating satellites. There were many available like the RS-10, RS-12, and RS-15 that could be worked with basic HF/VHF equipment. They were low orbiting birds so passes came and passed in as little as 4 minutes. I always found it quite difficult to find and tune in a station using phone so switching to CW usually netted me more contacts per pass. Ever since then I would say that about 95% of my HF activities have been with CW.
Now with indoor antennas I find that CW allows me to hear and work signals that are weaker due to the reduced performance. There have been many DX'peditions where they operate on all bands and all modes. I can usually hear them on CW but find it hard to pick their signal out when operating phone on the same band.


Digital Modes

RFI and digital modes
In my situation I have problems with PSK31 and RFI. Many times my PC will lock-up, programs will start themselves, and strange things can happen during transmission.
Thanks to modern technology and computer integration into the hobby, the digital modes have really helped when limited with indoor antennas. PSK31 is one mode where the error correction capabilities have really helped out. Plus, most PSK31 operation is at greatly reduced power which means you can run slightly higher than recommended power so that you can be heard. I have run PSK31 at about 30 watts and made many contacts without getting any reports of bad IMD.
RTTY is another mode of choice and FSK is recommended over AFSK. AFSK RTTY really uses SSB to transmit tones and I have found that any "Phone" mode generates more RFI both at the operating position and possibly with neighbors.
If you plan on operating using digital modes, how you cable your equipment is can make a big difference.
Always try routing RF cables away from computer cables. At my operating position, all RF cables come in above desktop height and go up. My PC and all of it's cabling is below desktop height.
Adding toroids around your keyboard and mouse cables to stop RFI at the PC.
Try using a different keyboard if you find RFI getting in. I had a no name type keyboard that went nuts when ever I transmitted. I switched that to a better keyboard (name brand) and eliminated the problem.

Phone (SSB)

I don't use phone much
I would say that the total number of phone contacts is only about 10%. I generally use it on 75 meters to check into a local net. The ROC City net is a local net, Wednesdays at 8:00 pm on 3.825MHz.
Many people give up when trying to use an indoor antenna because they use phone. Remember, phone isn't a full duty cycle mode. Your power is directly related to the amplitude of your voice and ALC settings of the radio.
Another issue with phone is that there is a greater chance of creating RFI that could affect both your equipment and your neighbors televisions, stereos, phones, and computer speakers.
Not being a big fan of phone operation I can only suggest that you do what ever works for you. Don't give up just because one thing doesn't work. Band conditions are constantly changing so choose the band that has the best propagation for that moment.
Pick stations that have strong signals. If I hear a station that's at least 3db above the noise floor I can usually log a good contact. If it's a DX'pedition, I generally wait till the end after some of the "feeding frenzy" has cleared out.
 



Wednesday, October 17, 2012

RF average, pulse and peak envelope power measurements


- a summary or overview of the different types power level measurements that can be made - average power, pulse power, peak envelope power, PEP.

RF and microwave power meter tutorial includes:
    •  RF / microwave power meter basics
    •  Average, pulse & PEP
    •  Sensor types
    •  RF power measurements


When measuring RF and microwave power levels it is necessary to understand the nature of the signal as this can have an impact on the power measurement and the instrument used.
Terms including: average power, RF pulse power, RF peak power and peak envelope power, PEP require different measurement techniques and as a result they need different sensor types to measure them.

RF average power

The most obvious way to measure power is to look at the average power. This is defined as the energy transfer rate average over many periods of the RF waveform.
The simplest waveform to measure is a continuous wave (CW). As the signal is a single frequency steady state waveform, the average power is obvious.
For other waveforms the averaging parameters may be of greater importance. Take the example of an amplitude modulated waveform. This varies in amplitude over many RF cycles, and the RF power must be averaged over many periods of the modulating waveform to achieve a meaningful result.
To achieve the required results, the averaging period for RF power meters may range from several hundredths of a second up to several seconds. In this way the RF or microwave power meter is able to cater for the majority of waveforms encountered.

RF pulse power or peak power

In a number of applications, it is necessary to measure the power of a pulse of energy. If this were averaged over a long period of time, it would not represent the power of the pulse. In order to measure the power of the pulse itself, a method of defined exactly what must be measured.
As the name pulse power implies, the power of the actual pulse itself is measured. For this the pulse width is considered to be the point from which the pulse rises above 50% of its amplitude to the point where it falls below 50% of its amplitude.
As the pulse is likely to include some overshoot and ringing, the most accurate term for the power is the pulse power. Peak power would imply that the value of any overshoot would need to be taken, whereas the actual power measurement required is that of the overall pulse.

Peak envelope power, PEP

For some applications another form of RF power measurement is required. Called peak envelope power, PEP, it is used to measure the power of some varying waveforms.
There are many instances where a power measurement that takes the peak of the envelope is needed. Many digitally modulated waveforms may require this, and also transmissions such as AM and Single Sideband may also need this type of RF power measurement.
The envelope power is measured by making the averaging time greater than the period of the modulating waveform, i.e. 1/fm where fm is the maximum frequency component of the modulation waveform.
This means that the averaging time of the RF power measurement must fall within a window:
It must be large when compared to the period of the highest modulation frequency.
It must be small compared to the period of the carrier waveform
The peak envelope power is therefore the peak value obtained using this method.

Summary

Of all the forms of RF power measurement, the average power is the most widely used. It is the most convenient to make, and often expressed the value that needs to be known. However pulse power, sometimes referred to as peak power, and also the peak envelope power also need to be known on many occasions. However the techniques and equipment needed to make peak envelope power and pulse power are different to those needed for average power. Accordingly it is necessary to understand the differences between the different types of RF power measurement and the equipment needed.

RF average, pulse and peak envelope power measurements


- a summary or overview of the different types power level measurements that can be made - average power, pulse power, peak envelope power, PEP.

RF and microwave power meter tutorial includes:
    •  RF / microwave power meter basics
    •  Average, pulse & PEP
    •  Sensor types
    •  RF power measurements


When measuring RF and microwave power levels it is necessary to understand the nature of the signal as this can have an impact on the power measurement and the instrument used.
Terms including: average power, RF pulse power, RF peak power and peak envelope power, PEP require different measurement techniques and as a result they need different sensor types to measure them.

RF average power

The most obvious way to measure power is to look at the average power. This is defined as the energy transfer rate average over many periods of the RF waveform.
The simplest waveform to measure is a continuous wave (CW). As the signal is a single frequency steady state waveform, the average power is obvious.
For other waveforms the averaging parameters may be of greater importance. Take the example of an amplitude modulated waveform. This varies in amplitude over many RF cycles, and the RF power must be averaged over many periods of the modulating waveform to achieve a meaningful result.
To achieve the required results, the averaging period for RF power meters may range from several hundredths of a second up to several seconds. In this way the RF or microwave power meter is able to cater for the majority of waveforms encountered.

RF pulse power or peak power

In a number of applications, it is necessary to measure the power of a pulse of energy. If this were averaged over a long period of time, it would not represent the power of the pulse. In order to measure the power of the pulse itself, a method of defined exactly what must be measured.
As the name pulse power implies, the power of the actual pulse itself is measured. For this the pulse width is considered to be the point from which the pulse rises above 50% of its amplitude to the point where it falls below 50% of its amplitude.
As the pulse is likely to include some overshoot and ringing, the most accurate term for the power is the pulse power. Peak power would imply that the value of any overshoot would need to be taken, whereas the actual power measurement required is that of the overall pulse.

Peak envelope power, PEP
For some applications another form of RF power measurement is required. Called peak envelope power, PEP, it is used to measure the power of some varying waveforms.
There are many instances where a power measurement that takes the peak of the envelope is needed. Many digitally modulated waveforms may require this, and also transmissions such as AM and Single Sideband may also need this type of RF power measurement.
The envelope power is measured by making the averaging time greater than the period of the modulating waveform, i.e. 1/fm where fm is the maximum frequency component of the modulation waveform.
This means that the averaging time of the RF power measurement must fall within a window:
It must be large when compared to the period of the highest modulation frequency.
It must be small compared to the period of the carrier waveform
The peak envelope power is therefore the peak value obtained using this method.

Summary

Of all the forms of RF power measurement, the average power is the most widely used. It is the most convenient to make, and often expressed the value that needs to be known. However pulse power, sometimes referred to as peak power, and also the peak envelope power also need to be known on many occasions. However the techniques and equipment needed to make peak envelope power and pulse power are different to those needed for average power. Accordingly it is necessary to understand the differences between the different types of RF power measurement and the equipment needed.

Removing RFI from Microphone Inputs


Many amateur radio stations today are experiencing terrific RFI (Radio Frequency Interference) that is impeding their audio signals and causing very garbled and distorted audio. Careful listening indicates that MANY SSB signals on the air today exhibit RFI - sometimes not enough for the other stations to notice (because they are listening on a 3" speaker in their transceiver), but careful listening in a wideband receiver with VERY high quality receiving equalizers and studio monitor speakers allows this slight interference to become VERY annoying. And, of course, there are also signals on the bands that have terrible problems with RF getting into their audio lines, causing all sorts of problems.

1. Shielding of the Mic Connector


We, here in the Heil Sound lab, have discovered a very interesting fact. Most of the major transceivers today do NOT ground their microphone shields! That's correct - the mic connector shields FLOAT! Now wasn't this one of the FIRST things we learned about building RF transmitters with speech audio sections? GROUND those shields!! So, we came up with a very simple fix that just about anyone can make to their rig. You don't have to get inside the radio, so you don't void any warranties. The fix is simple and effective.
This applies to the 4 and 8 pin Foster (that's the Japanese company that builds those dang little mic connectors!!) microphone connectors so common on today's rigs.
First, unplug your Heil (what - you don't have one yet??) microphone cable from the front panel of the transceiver. Do this first, because you don't want the mic plug connected to the sensitive circuitry inside the radio while you're soldering.
Remove the two small #4 Phillips head screws and the cable clamp they hold. Then remove the tiny Phillips head screw that holds the rest of the metal sleeve. Slide that back onto the mic cable. Now, cut off the end of a resistor, or get a piece of #20 solid, tinned wire about 3" long. Locate the mic pin that has the shield of the mic cable soldered to it.
With a small iron, carefully solder this solid wire to that shield and pin. Bring the sleeve back up the cable and attach to the connector with the small screw. This leaves the solid wire coming out the back of the connector. Replace the cable clamp, and (as you do that), tightly wrap that solid wire around one of the #4 Phillips head screws and tighten the clamp assembly very well.
What you have accomplished is grounded the shield to the transceivers chassis ground through the ring on the mic connector. (Make sure that ring is tight). This has been a big help to many stations with RFI problems and should help you clean up your signal.

2. Eliminating Common-Mode Current from Shields

Common-mode current can be a serious problem in amateur radio stations. This current, which can start flowing due to mutual coupling between an antenna and your coax, frequency-sensitive problems in your station ground, or a floating ground in your rig's power supply, can create any number of headaches, including RFI on your microphone line. In a nutshell, "ground" can "rise above ground" on some frequencies.
Several remedies are available.
A simple one is to wind a coil in your coaxial cable, about 8 or 10 turns of about 6" diameter, as close to the rig as possible. Hold the turns in place with black tape. This forms an RF choke like the one often used at the feedpoint of a dipole, Yagi, or Quad, and for the same reason. This choke can break up the current flow, and may have miraculous results (both in terms of effectiveness and simplicity!).
Another tactic is to slip snap-on ferrite cores onto the microphone line. On an AD-1 boomset adapter cable, snap one core onto the PTT line, another onto the microphone line, and another over the combined cable. If you are hearing RFI in your headphones, slip one or more cores onto the headphone line.
Earlier, it was mentioned that your rig's power supply might be involved. Many power supplies, especially switching-mode types, use a floating ground. A number of Astron® power supplies, which are very popular because of their low cost and excellent performance, use a floating ground. This can cause an amateur transceiver to take off scanning when you transmit, or set up common-mode current. The solution is to connect a short strap from the power supply's Black (negative) output terminal to the chassis of the power supply (often there is a convenient ground lug inside the cabinet). Then, connect 0.01 µF and 0.001 µF 50-Volt disc ceramic capacitors from the red ( + ) to the black ( - ) output terminals; the capacitors will shunt any RF on the DC line to ground, which now really is ground. Please use caution when doing any work inside your power supply, and utilize the services of a qualified electrician if you have any doubts about your capabilities. Heil Sound, Ltd. specifically disclaims any responsibility for personal injury or damage to equipment caused by improper modification work on station components.


Grounding Systems in the Ham Shack - Paradigms, Facts and Fallacies

Content provided by: Jose I. Calderon, DU1ANV - Makiling Amateur Radio Society. Member: Philippine Amateur Radio Association (PARA).  Reprinted with permission of the author

Through the years, I have been hearing problems from fellow hams over the air, and even in personal eyeball communications, about how they can organize and implement a good and effective Radio Frequency Interference (RFI) free grounding system in their ham shack. Some of these problems I heard are in parallel to the same problems I experienced in my early years of this hobby. Most new hams who operated mostly in the VHF and UHF band enjoyed their operating until later when they upgraded to the HF bands, and problems immediately cropped up. The first time they pressed the PTT and start talking in front of the microphone, all active equipment in the shack went haywire. Panel meters went crazy, the power supply volt meter jumped up and down, and if he was unlucky, he may have got his first microphone bite to shock him by surprise if the base microphone case was metallic.

Organizing an effective grounding system in the ham shack requires the ham radio operator to address the two major aspects of grounding. They are:

  • First - Compliance with electrical safety guidelines (electrical grounding system), and
  • Second - Dealing with RFI in the shack (RF grounding system).
In general, most newcomers to Ham Radio do comply with the first aspect in the context of electrical safety but often neglect the aspect of reducing the excessive presence of RF energy within the shack. Many believe that complying with good electrical safety guidelines is enough to dispel other operating problems. Though seemingly true, this notion is in fact a fallacy. Some of the problematic signs and symptoms of poor RF grounding in the shack that degrade the quality and satisfaction of operating ham radio equipment are enumerated below:
  1. Microphone bites (nasty RF shock!)
  2. Gritty and or fuzzy audio modulation (Distortion)
  3. Malfunction of electronic keyer (sending wrong characters)
  4. RF shock when touching metallic objects within the shack
  5. Power supply jitters (the regulated power supply becomes un-regulated!)
  6. Crazy SWR meter readings
  7. Desktop computer going crazy
  8. PC Desktop monitor jitters
  9. Fluorescent lamp flicker
  10. Active TTL switch circuit going crazy (Turning ON-OFF-ON by itself)
  11. Inactive panel meters of separate equipment moving on their own
  12. When transmitting, a distorted audio is heard over the amplified speaker of the PC desktop.
  13. Severe Radio Frequency Interference (RFI) to home appliances within the vicinity of the Ham shack.
All of the above are the major signs and symptoms of the presence of high RF voltages within the immediate vicinity of the ham shack when the transmitter is active. And these are all attributed to poor RF grounding. All conducting objects will absorb RF energy through coupling and will re-radiate the same. One can say “But I have already a very good electrical ground!”….. Fact? Or fallacy?
If you experience any of the above problems within the shack, I am pretty sure that you are suffering from a plethora of grounding and Un-Grounded ham shack problems. Let us analyze some scenarios of grounding systems typically complying with good electrical safety but which are poor RF grounding systems. An anthology of a simple case scenario and a worst case are presented and the possible problems that may arise at the instance the transmitter becomes active.


Scenario 1 (Simple case paradigm)
This ham operator was a neat fellow. One day, he finally convinced the xyl to let him setup his own radio shack, away from the prying eyes and itchy fingers of the family kids. And so he built his own radio room on the ground floor of the home QTH. He arranged his equipment and built a good electrical ground system by laying out a heavy copper wire about 3 meters long just behind the neatly lined up station equipment. He decided to run the ground wire straight so that each equipment ground lug can accommodate a short flexible grounding wire to reach the ground bus. He did this to all of the station equipment with a very neat connection so that the individual grounding wires did not get meshed up and entangled. The remaining length of the ground bus wasled outside to an effectively driven ground rod just outside, near the wall of the Radio room. This grounding setup looked like the one shown in Fig. 1.
Figure 1.

When everything was in order, he fired the 100 watt transceiver and begun transmitting in J3E mode by calling another station at 7.035 MHz. To his surprise, the station operator at the other end responded to tell him that his signal was S9 but the audio was garbled, gritty and fuzzy. Further adjustment and tweaking the ALC and mic gain controls did not solve the problem. He further observed that by reducing the RF power to 50 watts PEP, the problem disappeared. But when he switched on his linear amplifier to give 250 watts PEP output, the problem returned and became even worse. The two stations spent almost two hours of adjusting “this” and “that” but alas, to no avail. Just as our good and neat fellow ham was about to retire after a frustrating day, a third ham who has been monitoring the exercise came on frequency, and then politely said “You may be suffering from a “POOR GROUND”…. The problematic ham answered “What?... I have a perfect ground system”. He then described his new and neatly connected grounding setup”…. "Hmmmm…." said the third ham “You may have GROUND LOOPS! ”…Then he proceeded to explain why. During the long QSO exchange, the problematic ham learned the following:

Ground loops are formed when the individual ground wires of each equipment are:
  1. Ground loops are formed when the individual ground wires of each equipment are connected to the main ground bus at a point that is distant from each other (see Fig. 1)
  2. The individual station equipments already have their own ground reference but when they are interconnected, grounding each equipment to the main ground bus as shown in Fig.1 creates GROUND LOOPS. Each time a ground loop is created, a small inductive coil is formed (the ground wire completes the loop).
  3. When the ground loops are in the near field of RF energy (During transmit mode), these loops will couple to the RF energy (called RF coupling). As the RF energy is coupled to each loop, a fluctuating voltage is induced in unison with the burst of audio modulation of the RF energy. This energy will flow within the system and will seek the least resistance by following the associated circuits and eventually creeping into other internal circuits.
  4. Once the RF is inside these circuits, it will interfere with the normal operating parameters of sensitive circuits thereby creating havoc. RF bleed-over escaping from long interconnecting coaxial cables may also flow within each loop, bathing the whole shack with RF energy.
  5. His new ham shack has an excellent DC electrical ground system but has a VERY POOR RF GROUND SYSTEM!
Finally, the Elmer suggested to him to try the following:
  1. Dismantle the present ground wire configuration.
  2. Remove the long ground bus and terminate all ground wires from each equipment into a single point near your ground rod.
The problematic ham scribbled quickly in a piece of paper and came up with a final wiring that looked like the circuit shown in Fig. 2.

Figure 2.

They both agreed on the modifications and promised to contact each other at the same time the following day and then signed off.

Came the following days contact, the problematic ham called the Elmer and got an immediate reply. "Hey ol’ man", the Elmer said, "you have a beautiful signal, clean and kicking!" After a short pause came a reply… "Yeah thanks!" They exchanged an extended pleasant QSO and finally parted. The audio problem was solved and he was happy ever after.


Scenario 2 (Worst case paradigm) - The Un-grounded Ground
One day, during the next several rag-chew sessions on the same band, a third station joined the QSO. His signal was strong but the audio was also thin, fuzzy and garbled every time he raised his voice over the microphone. RF was all over the ham shack. He told the Elmer that every time he spoke over the microphone, the voltmeter of his regulated power supply jumped up and down the scale. The screen of his computer became fuzzy, and his lips were bitten with electrical shock if they touched the metallic case of the microphone. One night, while working a DX QSO, his Xyl came to the shack to give him the regular good night kiss. Holy cow! She and he received a mild electric shock the moment her lips touched his ear lobe! Also, he was threatened several times during the early evening QSO sessions by marble sized stones dropping and rolling down his roof top apparently thrown by close neighbors irked by the RFI to their TV, stereo and radio sets. Each time he transmitted, his Donald duck’s voice was heard over their radio sets.

He told the Elmer that he was monitoring silently (Just reading the mails, so to speak) the previous exercise (In scenario 1) but did not bother to break-in so as not to disrupt the lecture over the air. Nevertheless, he told the Elmer that he followed to the letter the previous over the air advice but still his station suffered from a serious RFI problem within the shack. After describing his grounding setup, the Elmer said, "Aha! You have an ungrounded ground!” In a quick response, the third ham said, "What?... But I have a ground!". While listening meantime to the surprised ham, the Elmer drew in his mind the setup as described. This ham had his shack installed on the second floor of the house. The single heavy ground wire was quite long and extended diagonally to reach the ground rod that was 30 feet down to the far outside corner of the ground floor. His grounding system looked like the setup shown Fig. 3 below:

Figure 3.

In the next “over”, the Elmer said, “It will take us quite long to discuss the reason why you have an ungrounded ground system. I suggest that I will send you a quick E-mail”….. When it comes, please read carefully and understand the explanations…. Asked his E-mail address, and then said 73….

The troubled ham received indeed the much awaited E-mail. Like a snorting bull, he retrieved quickly the attached document and begun reading the contents. The attached document read:

Dear troubled ham,
Further to our previous QSO, herewith please read and understand the explanation why your grounding setup is UN-GROUNDED! To understand why, please examine the drawing of its electrical equivalent circuit as shown in Fig. 4 below:

Figure 4.

The Elmer continued ……
Your ground wire is 30 feet long (9.1 meters); this length is very close to a quarter wavelength at 7 MHz. When you start transmitting at this frequency, your transmitter setup and antenna system will create an image of standing wave throughout the length of this wire. This is by virtue of the RF voltage induced due to resonanceIf the long ground wire is ¼ wavelength long at the transmit frequency, this wire will resonate and will act as a radiating element. If the ground wire is less than a quarter wavelength, it will appear as an inductive reactance, the value of which is “Zero” (point “A”) at earth ground and “High” at the circuit ground point of the equipment (See Fig. 4, point “B”).

If the wire is exactly ¼ wavelength of the transmitting frequency, the ground wire will act like a resonant LC circuit with very highimpedance at its top (point “B” in Fig. 4). This reactance will appear like a resistance (called Impedance) to impede the flow of RFcurrent to earth ground, bringing the ground return of all the station equipment to float above the earth ground as if the ground wire is not there (or, as an insulator at RF). Since one end of the wire leads directly to earth ground (Zero Impedance), it follows that the top of this wire (at the circuit ground point of the equipment marked as “B”) is the high impedance point (High Z). The voltage standing wave that appears at any point along the length of this wire at the resonant frequency is:

Now, as we go back to antenna basics, and reviewing Mr. Ohm’s power formula as shown above, the voltage that appear at point “B” will be determined by the following parameters:

  1. The power of the transmitting equipment.
  2. The equivalent impedance value at point “B”.
  3. The length of the ground wire in wavelengths.
  4. And, the extent of RF to earth ground leakage existing in the whole setup in the shack.
For calculation purposes, let us assume that there is a ground leakage (Equipment ground to earth ground). Due to the condition of the shack (furniture’s, operating table, concrete floors and walls etc…all these are somewhat touching earth ground), the impedanceat point “B” is for example equal to 1000 Ω. Then, the induced voltage at this point when the active transmitter output power is 100 watts, will be:
Hmmm…. That’s the reason why you have RF in the shack! Because you have an “ RF UNGROUNDED GROUND! Hi hi…."
Of course this is true only if a ground leakage is present. If there is none, during the dry season for example (where moisture and humidity is nil) will aggravate the situation. The impedance at the top of the ground wire will increase somewhere to 1500Ω or thereabouts. Therefore, under this condition and by interpolation, the voltage at point “B” of your setup will be
Below (See Table 1) are the voltage standing waves that develop at point “B” if you use different lengths of ground wire and, if the same parameters exist in your shack. The voltage values were calculated by interpolation using the wavelength factor.



Table 1.

You are living in an extreme RF environment! You are lucky that you and or any of your family are not wearing a “pacemaker”. Otherwise, %$#@#!! You are somewhere in the fields of ambrosia by now! That level of RF in the vicinity of your shack will create havoc within its reach. Your own safety and the whole gamut of station equipment will be affected. Note also that whenever you increase transmit power, the voltage standing wave at point “B” will also increase!

Of course, the above exercise in Table 1 is true if the actual impedance at point “B” is 1000Ω. Other impedance values will give a result of voltages other than those shown. Any load connected at this end will change the impedance value but the voltage ratios between the short and longer wires will remain the same. Bear in mind that the impedance at the open end of a ¼ wavelength wire is about 2000-3000Ω. The example above is based on these assumptions but it will approximate the actual values. In these calculations, the power transfer loss was not considered to simplify the example and emphasize the voltages so created.

Also, if there is a wide mis-match between the antenna feed point impedance and the transmission line, a high voltage standing wave will result to a high VSWR at the antenna system tuner output terminal. This standing wave will aggravate the situation because this voltage will add up to the already existing standing wave created by the long ground wire. The result is catastrophic!. RF is all over the place…..

My recommendations:
  1. Relocate the ground rod to be nearer to the shack so that the ground wire will be as short as possible and will not resonate.
  2. Use a short length of ground wire that will not be ¼ wavelength (or its odd multiples), or close to it, of the operating frequency. This is also the reason why your transceiver manual recommends not using this length of ground wire!
  3. Install the ground wire so that it will be far from telephone lines and main house wiring to prevent coupling of residual RFenergy.
  4. Relocate the ground rod and drop the ground wire through another location to be as far as possible from your close neighbor.
  5. Match your transmission line impedance equal to the feed point impedance of the antenna or as close as possible to reduceVSWR at the tuner’s output terminal (Take note: not the input terminal of the tuner! Because all tuners measure only theVSWR at the transceiver side)
I look forward to hearing your signals soon……
73s…
The Elmer

Three days later, and during the next weekend rag-chew, the troubled ham reappeared on frequency. The Elmer acknowledged him with this comment; Hey ol’man! Your signal is fantastic with booming audio. Crystal clear! What did you do this time? After a short pause, the troubled ham answered….. Yeah I have a new friend! Who? The Elmer asked. The troubled ham said…. my close neighbor! Many thanks hi hi! I followed your recommendations! They all continued the round-table QSO and happily exchanged notes. The Elmer learned that this ham had eventually relocated his ground wire, the length of which is now only 3 meters long. It was still a little bit long but the power supply jitter was gone and the RF bleed-over to the microphone circuit disappeared when transmitting at 100 watts PEP. The Ham was elated and thanked again the Elmer.


Addendum
Dealing with high RF in the shack has no simple answers but the paradigms exemplified in the above scenarios presented the basic concepts and remedial solutions to a seemingly perfect grounding system. Most new comers in ham radio forget the basic fundamentals of radio and the behavior of physical entities within the ham shack when exposed to RF environment. Forgetting the basic fundamentals and failure of the ham to apply these principles and fundamentals to actual practice predisposes poor safety practice, danger from exposure to high levels of electromagnetic radiation and destruction of equipment and other station accessories due to poor RF grounding techniques. That power supply in the worst case scenario will self destruct eventually due to the presence of high levels of fluctuating RF leaking into the sensitive regulator sensing circuit. Due to poor regulation, the transceiver will follow to say “goodbye”. The scenarios presented are extreme examples of real life experiences in ham radio practice. The two paradigms presented the basic problems and how to deal with each to reduce the presence of high RF levels in the shack. To exploit the complete elimination of RF down to zero levels will be a great feat, if not impossible, but reducing the RFI to such levels that will not interfere with sensitive equipment and circuits is enough to ensure safe and complete satisfaction to a continuing hobby.

The notion of having a good electrical DC ground return is enough to ensure safety in Ham Radio is a fallacy. This was consistent in the scenarios presented where no provisions were considered to reduce the presence of RF in the shack. Of course, one can consider that the solutions presented merely reduces the possibility of coupling (the ground loop) and the reduction of high voltage standing waves due to the use of long ground wires (the un-grounded ground) that are equal or close to a quarter wavelength at operating frequency. Perhaps several questions that will arise from the lessons learned in the two scenarios presented maybe anticipated as follows:
  1. What if the troubled ham in scenario 2 cannot relocate his ground rod to be closer to the shack?
  2. What other recommendations can the Elmer suggest if the ground wire cannot be shortened?
  3. What if the RFI still persist after doing all the remedial measures recommended in Scenario 1 and 2?
These are good anticipated questions. Not all amateurs are lucky to have their ham shacks installed in the ground floor of their home QTH. Many are the so called “Cliff dwellers”, meaning that their shacks are located in elevated floors, such as the third floor or higher in apartment buildings and condominiums. Such cliff dwellers may not have the benefit of shortening their ground wires towards earth ground. In spite of this situation, there are still effective measures to consider. Some of these are new and some are as old as the age of the ham radio world.

The Elmer is nowhere to contact this time but this author will take the opportunity to answer the first two questions. There are two effective alternatives. They are:

Alternative 1 - The Counterpoise
This grounding technique is as old as the age of Ham Radio. The use of this technique dates back as early as 1895. It is used more effectively when earth ground conductivity is poor. But since your antenna per se also needs an RF ground to propagate efficiently at that higher elevation above earth ground (the reason of which, is beyond the scope of this article but maybe covered in future articles), it can be installed to perform the two functions. That is, to provide an artificial ground for the antenna when elevated high above earth ground and, to keep RF away from the station equipment. The setup is presented in Fig. 5 below.

Figure 5.


Let us imagine that you want to operate on 4 amateur bands, namely 40, 20 15 and 10 meters. The installation procedure is given below:
  1. Cut each individual counterpoise wire exactly ¼ wavelength of each operating frequency.
  2. Connect one end of each to the single ground point terminal (see Fig. 5).
  3. Leave all the opposite ends free and floating (no connection). For better efficiency, stretch and spread each wire in a radial fashion, away from the station equipment as shown in Fig. 5. The position and orientation of the wires is not however critical so that you may want to anchor each at the side wall of the apartment building (of course you have to insulate the ends by using small egg insulators). Another alternate is just to let each wire dangle downwards but still the wires must be spread out. How you will do it will depend on your prolific imagination.
  4. Now, look for the longest wire (maybe the ¼ l 40 meter band counterpoise) that can reach the ground rod and designate this as your electrical ground. The idea is to use this wire to connect to your ground rod through a knife switch. When you are operating the station, the knife switch must be in open position. But when you stop operating and for safety reasons, you must provide an electrical ground. Run downstairs and close the switch. Remember however, to always open this switch whenever you sign ON the station.
The Principle of the counterpoise – In the older times, this contraption is used to complete the so called “Marconi antenna” which in effect is a quarter-wave antenna. In order to satisfy resonance, proper matching and efficient radiating properties, a quarter wave element is added to complete the antenna circuit. This is similar to today’s radial system that is installed in quarter-wave and 5/8 wave antennas that are elevated above earth ground. We can use the same technique in keeping away RF from the station equipment. The electrical equivalent circuit is shown in Fig. 6 below:

Figure 6.

The counterpoise is in effect an artificial ground. One end of the quarter wavelength is connected to the circuit ground of the system (RF generator or transmitter) and the other end is left floating. When the RF generator is active, an image of the signal is developed in this wire and a voltage standing wave is induced. The magnitude of this voltage is similar to a ¼ wavelength antenna at various points along its length. The open end of this wire is high impedance (refer to antenna theory) while the opposite end that is connected to circuit ground of the generator is zero. It follows that the voltage at the generator side is zero (circuit ground) and the open end is high voltage.
Notice that the high RF voltage point is now the reverse of the voltage points developed in the case of scenario 2 (See Fig. 4). By taking advantage of this characteristic, the use of the counterpoise will shift the high voltage away from the station equipment. Ifeach operating band has its own separate counterpoise, then each respective counterpoise will function as the operating band is changed, allowing multi-band operation and preventing severe RFI in the shack.
CAUTION! ---- The counterpoise wires will radiate RF energy. Make sure that the end of any of the wires will not extend near home appliances within your house and or near your close neighbors.


Alternative 2 -The RF Suppressor Ground System
This is the modern version of an ingenious device developed and introduced by several hams in recent years, notably by William Chesney/N8SA (See http://www.hamuniverse.com/grounding.html) who published the article in 2003. This grounding system addresses both the electrical ground and RF grounding requirements in Ham radio. The device is intended for long grounding wires. The grounding device utilizes a coaxial line where the ground wire is enclosed by a shield, such as RG-8 transmission line, to prevent the buildup of high voltage standing wave near the station equipment. This ground line is not length sensitive and can be used at any length without concern. It will keep out RF away from the shack. The wiring setup of this practical grounding system is shown in Fig. 7 below:

Figure 7.

Installation of the RF suppressor – Remove the existing ground wire and replace it with a length of RG-8 coax transmission line, enough to reach the ground rod and into the shack to connect to the ground bus. At one end, short (solder) the coax shield to the center conductor of the RG-8 and the remaining pig tail to be connected (soldered) to a short heavy gauge solid copper wire to reach the ground rod (See Fig. 7). At the other end, strip the coax to reveal the center conductor and remove part of its shield. Connect the center conductor to the circuit ground of the equipment. Leave the coax shield open at this end but connect a ceramic disc capacitor(Marked as C1 = 0.001 to 0.1 μF / I Kilo Volt). One terminal of this capacitor is connected to the coax shield and the other terminal to the center conductor (See Fig. 7). The RF suppressor ground system is now complete.

Of course the capacitor value is selectable depending on the lowest operating frequency band and length of Coax. The correct value is selected until RF disappears in the shack (at the lowest band). Or, when your lips doesn’t get to be burned or electrocuted (when touching the metallic mic case) as you speak or transmit. However, YOU MUST USE A HIGH VOLTAGE CAPACITOR RATING, about 1KV minimum, but the higher the better. Otherwise, ZAPPP!!!, this capacitor will explode if a surge of high voltage standing wave will develop instantaneously at or above 500 volts at this terminal.

The circuit shown in Fig. 7 is an effective RF grounding setup. The author’s shack is in the second floor and uses the same grounding system which has been in use since 1989 with no RFI in the shack even when the 1 KW linear amplifier is in use. DU1FLA/Estoy uses the same grounding system. We used a .01 μF / 1Kv capacitor for C1.

Principle of the RF suppressed grounding system – By inspection (see Fig. 7), the ground wire is enclosed effectively by the coaxshield so no high voltage standing wave can buildup in this wire. However, since the shield is exposed and floating, a high voltage standing wave will appear at the outer surface of the coax shield. This voltage is Zero at the shorted end (ground rod terminal) and high at the open end. When you connect a capacitor between the high voltage end of the coax shield and the center conductor (See Fig. 7), the impedance of this capacitor is very low at the operating frequency, thus acting as a low impedance load (By virtue of its low reactance = Z, in Ohms) between the shield and center conductor. The RF current will flow easily through this capacitor and is diverted to the center conductor enclosed by the shield and finally to earth ground. The buildup of high voltage standing waves between the inside surface of external shield and the center conductor is suppressed because the characteristic impedance of the RG-8 is only 50-52Ω. And, the voltage drop across the external capacitor (C1) between the open end of the shield and center conductor is;
The combined parallel reactance of this capacitor and the total cable capacitance of the RG-8 transmission line will even decrease further the voltage drop. Also, as the operating frequency goes higher, the reactance of C1 will decrease. Hence, the voltage drop will be even lower. That is, as if the long physical length of coax ground wire is just about less than 1 meter long, electrically (See Table 1).

The voltage attenuation curve at higher RF operating frequencies above 7.035 MHz will in fact proceed at the rate of minus 6 dB per octave. This means, when the operating frequency is doubled (14.07 MHz); the voltage that exist across C1 will decrease to ½ the original amplitude. Further, because the center conductor of the coax line is connected directly to earth ground, it becomes automatically your electrical safety ground. How do you like that?

What we have presented and discussed dealt only on how we will keep out the troublesome RF energy near our equipment as far as ground loops and RF un-grounded grounds! But how we will make a good and effective RF earth ground to work with the antenna system during transmitting and receiving (Your system needs it whether you like it or not!) is another matter. In order to have an effective propagation for DX work requires a good RF earth ground setup. Merely having improved your equipment ground to earth ground is not a guarantee that you have also an effective RF earth ground….. Another fact!

Improving and or making a good RF earth ground to work with your antenna system is another topic that is not covered by this article. Similarly, to answer the anticipated question number 3 also requires a separate topic for another article. Dealing with numerous causes of RFI due to “near field effects” and gross exposure of ham equipment to high RF fields that are not caused by improper grounding systems, though somewhat related, is a separate subject. Available space does not warrant the extension of these topics but hopefully, these will be covered separately in future articles.

It is hoped that this article has enlightened the reader to understand the importance of effective grounding paradigms and, the facts and fallacies of grounding in ham radio. To make a shack RF free coupled with sound electrical grounding technique is a responsibility of the amateur operator to address the aspects of grounding when dealing with high levels of RF energy in the operating environment. Effective grounding of equipment is mandatory to address the issues of personal Safety, damage to sensitive equipment and prevention of severe RFI in the operating community.
Related Posts Plugin for WordPress, Blogger...