28/07/2009 - Pengetahuan AM

1. Tahukah anda?..Apabila kita membuang air kecil, badan kita akan menjadi sejuk kerana telah melepaskan haba melalui bahan kumuh. Jika kita mengencing orang lain, maka haba akan terlepas dari badan orang itu lalu kita akan dilempang olehnya.

2. Percayakah anda?..Wanita mengelipkan mata dua kali lebih kerap daripada lelaki dan jantung wanita juga berdegup lebih laju berbanding jantung lelaki. Tapi percayakah juga anda bahawa, lelaki selalu ada dua mata air dan jantung mereka juga berdegup dengan lebih laju jika diketahui oleh isteri.

3. Terdapat kira-kira 3,000 spesis pokok dalam setiap kawasan seluas 1.6 km persegi di hutan Amazon dimana jika seseorang bernama Saiful memasuki kawasan itu, beliau berkemungkinan akan tersesat selama 3,000 jam jika tidak membawa kompas.

4. Uri Geller, ahli psikik terkenal yang dilahirkan pada 20 Disember 1946, mengatakan bahawa kebolehan luar biasa yang dimilikinya itu berasal dari planet Hoova dan kadangkala dia juga memekik sambil mengatakan yang dia adalah seorang Ultraman!.

5. Tahukah anda?..Manusia hanya menggunakan 10% daripada otaknya. Tetapi ini tidak bermakna baki 90% lagi perlu dibuang kerana jika dibuang sudah terbuktilah manusia itu dari jenis yang tidak ada otak!!.

6. Apabila marah, Tasmanian Devil (sejenis haiwan yang hidup di pulau Tasmanian, selatan Australia) akan bertukar warna menjadi kemerah-merahan. Bila Makcik Leha marah, wajahnya juga akan bertukar menjadi kemerah-merahan padahal mereka bukanlah dari spesies yang sama.

7. Gelas kaca pecah dengan kelajuan 4,827 km/j. Pecah Kaca, Pecah Gelas, Sudah Baca Harap Balas pula ialah ayat yang selalu diguna oleh budak-budak sekolah ketika bercinta.

8. Tahukah anda?..Otak kita mengandungi 80% air. Walaubagaimanapun. .seseorang yang sudah lama tidak membuat hubungan kelamin bersama isteri akan mengalami satu sindrom yang berkaitan otak iaitu sindrom masuk air.

9. Tahukah anda?..Belang yg kita lihat pada harimau bukan sekadar pada bulunya tapi pada kulitnya. Belang pada lelaki berhidung belang pula bukan sekadar pada hidungnya, tapi juga pada bulu hidungnya.

10. Tidak ada satu pun perkataan yang bermula dengan huruf 'W' dalam bahasa Sepanyol. Sementara itu, hanya terdapat 12 huruf dalam bahasa Hawaii iaitu A,E,H,I,K,L, M,N,O,P,U dan W. Untuk pengetahuan juga, didalam Bahasa Inggeris dan Melayu mesti menggunakan ke semua huruf dari A-Z kecuali yang buta huruf kerana mereka tidak tahu membaca.

11. Hanya ada empat perkataan sahaja dalam bahasa Inggeris yang berakhir dengan bunyi-'dous' iaitu tremendous, horrendous, stupendous dan hazardous. Ini membuatkan seseorang yang bernama Fidaus berasa bangga sekejap.

12. Tahukah anda?..Di negara Norway, terdapat sebuah tempat di panggil Hell (neraka) manakala kalau kita berbuat jahat selalu, tempat yang kita akan pergi juga bernama Hell.

13. Menurut kajian ahli sains, secara puratanya, kita akan berhenti bercakap setiap tujuh minit. Tetapi menurut seorang ahli sains yang lain yang bisu sejak lahir, secara puratanya, dia tidak boleh langsung bercakap seumur hidupnya.

14. Siapakah Thomas Mapother?? Lelaki itu adalah pelakon tampan, Tom Cruise, sebelum dia menukar namanya. Siapakah pula Latiff Sufian?? Lelaki itu pula ialah cuma seorang tukang kebun di Sekolah Rendah Kampung Kerinchi.

15. Untuk mengekalkan suhu sejuk, burung unta akan mengencingkan kakinya sendiri supaya ia akan berasa sejuk apabila air itu menyejat. Anda juga boleh berbuat demikian jika hendak berbau hancing.

16. Dipetik dari kenyataan sebuah majalah, tembakau membunuh lebih ramai rakyat Amerika (seramai 450,000 orang) setiap tahun berbanding alkohol, kokain, heroin, homisid, bunuh diri, kemalangan kereta, kebakaran dan AIDS. Untuk menyembunyikan rasa takut dikalangan orang-orang kaya pula, majalah tersebut tidak berani untuk mengatakan bahawa tembikar yang di beli dengan harga yang mahal juga mampu membunuh jika dihentak dikepala dengan kadar yang kuat.

17. Tomato dan Timun adalah buah-buahan ya, bukan sayur. Taugeh dan Sawi pula ialah nama samaran pelukis majalah kartun Ujang ya, bukan Utopia.

18. Agensi keselamatan antarabangsa mengatakan jangan takut untuk menaiki kapal terbang kerana ia merupakan alat pengangkutan yang paling selamat. Ia jauh lebih selamat berbanding motosikal, bas, kereta api dan kereta. Akan tetapi agensi itu mungkin terlupa akibat jikalau kapal terbang itu terhempas ke atas jalanraya dan menimpa semua orang yang menaiki kenderaan yang disebut tadi adalah kebarangkaliannya akan hancur lebur.

19. Jangan terkejut, kalau diceraikan satu per satu dan kemudian disusun semula, seluruh batu yang terdapat pada Tembok Besar China, cukup untuk mengelilingi bumi pada garisan khatulistiwa dengan ketinggian 2.5 meter dan jangan terkejut dengan penceraian artis-artis tempatan kerana itu semua publisiti murahan yang dapat menaikan populariti pada carta bintang paling popular.

20. Mengikut fakta, sebelum era Masihi, terdapat satu perkidmatan 'pos laju' menggunakan kuda di Parsi. Posmennya akan memakai pengikat kepala dan menghantar surat tersebut merentasi Asia, beratus-ratus km tanpa henti. Mengikut akta pula, seorang Posmen yang menaiki EX5 merah dari Pos Malaysia, jika selalu berhenti-henti minum kopi di kedai mamak boleh diberhentikan kerja serta-merta.

21. Dianggarkan sel kulit yang mati yang hilang sepanjang hayat kita cukup untuk mengisi lapan beg tepung seberat tiga kilogram dan tepung itu kalau di buat roti canai, rasanya amat lazat jika dimakan bersama-sama dengan kari kepala ikan.

22. Ini adalah benar, ngauman seekor singa mampu didengari sejauh 3 km kecuali orang yang pekak walaupun dia hanya berada 3 cm sahaja dari singa tersebut.

23. Permukaan bumi adalah seluas 153,295,000 km persegi manakala orang yang jauh perjalanannya sewaktu berkelana seperti Azroy dari filem Gila-Gila Remaja pula hanya mendapat luas permandangan memandangkan dia hanya mengelilingi Kuala Lumpur sahaja.

24. Tahukah anda?..Seekor lembu kentut sebanyak 200 kali lebih banyak berbanding manusia. Tetapi ini tidaklah ada apa-apa berbanding dengan kentut seorang manusia yang bernama Faizal, tidak berbunyi tapi busuk.

26/07/2009 - Int. Lighthouse & Lightship Weekend 2009

Malaysian Nation Wide Light House Weekend 2009 (MLHW 09), and International Light House Ham Radio Weekend 2009

Hi All,

Our friend intends to do an International Light House Ham Radio Weekend and he has prepared the paper below for your attention.

Enjoy reading -

Purpose:
i. This event is not a contest, there are no prizes or any other enticements to participate and is therefore free of charge.
ii. To promote public awareness of ham radio and lighthouses in Malaysia.
iii. To acknowledge the contribution and recognition of the lighthouses and their keepers.
iv. To foster fellowship among members of the various Ham Radio clubs and Lighthouse Societies in Malaysia.
v. To gain experience for DX-peditions for the Ham Radio operators and to promote “exotic” Malaysia among International DXCC chasers or seekers.
vi. Pilot project proposed, as a future yearly event on the 2nd weekend of August and to be inserted in the Tourism Malaysia Calendar of the year.
i. Since the 2nd weekend of August every year, coincides with the “Asia Pacific JOTA”, this ILLW event is extended to all Boy Scouts and Girl Guides via BP House Malaysia, to join in the fun at the light houses or contact the light houses via Ham Radio.

Date: 1st till 31st August 2009 (MST)
1. Weekend 2 – 8 Aug 09 (Sat), 9am till 9 Aug 09 (Sun) 3pm (30hrs)
2. Weekend 3 – 15 Aug 09 (Sat), 9am till 16 Aug 09 (Sun) 3pm (30hrs)

Collaboration with:
1. Jabatan Laut Malaysia
2. Kementerian Belia Dan Sukan
3. Suruhanjaya Komunikasi dan Multimedia Malaysia
4. Kementerian Pelancongan & Tourism Malaysia
5. Pejabat Menteri Besar & Local Council
6. MARTS
7. MARES
8. ASTRA
9. NESRAC
10. JASRA
11. PERAMAH
12. BARC
13. Kinabalu Radio Club
14. SARC
15. Kuching Radio Club
16. Brunei Darrusallam Radio Society
17. SARTS
18. All other groups within Malaysia

Light Houses Station Master:
1. Penang
1. Rumah Api Fort Cornwallis, 9M2BA – Azmi Abdullah
2. Rumah Api Muka Head
3. Rumah Api Pulau Rimau
1. Selangor
1. Rumah Api Pulau Angsa 9M2CJ – Thiam Chee Ming
2. Rumah Api One Fathom Bank
3. Rumah Api Kuala Selangor 9M2SQL – Abdul Mutalib Omar
4. Rumah Api Bukit Jugra 9M2JEN - Saiful, 9M2ONE - Aziz

1. Negeri Sembilan / Melaka
1. Rumah Api Cape Rachado 9M2QQ – Hans Elhers
2. Rumah Api Pulau Undan 9M2WT – William Tan
1. Johor
1. Rumah Api Bukit Segenting 9M2NP - Tango (Narayanan Pillai)
2. Tanjung Piai Lightbeacon
3. Pulau Pisang Light House
4. Tg Api Api Light House 9M2DA Deen Atan
5. Tg Tenggaroh Light House
6. Pulau Mungging Light House
1. Pahang
1. Rumah Api Tanjung Gelang 9M2TOT Ibrahim B Musa
1. Kelantan / Terengannu
1. Tumpat Light House
2. Pantai Senok . Pengkalan Daty Light House
3. Seabelle Rock Light House, Pulau Perhentian
4. Bukit Puteri Light House Kuala Terengganu
1. Sabah
1. Tanjung Kubong Light House 9M6DJC – M Christoper
2. Pulau Papan Light House
3. Pulau Gaya Light House
4. Pulau Kalampunian Light House
5. Pulau Silingan Light House
6. Tanjung Trang Light House
7. Bagahak Light House
8. Pulau Si Aimil Light House
1. Sarawak
1. Tanjung Dato Light House 9M8DB – Johnny
2. Tanjung Po Light House
3. Tanjung Jerijeh Light House
4. Tanjung Sirik Light House
5. Tanjung Kidurong Light House
6. Tanjung Lobang Light House
7. Tanjung Baram Light House


ITENERARY FOR ILLW AT JUGRA LIGHTHOUSE

Date/Time Start: 15/8/2009 , 9am
Date/Time Finish: 16/8/2009, 3pm
Locaton: Jugra Lighthouse, Banting
Accomodation: Bring your own tent
Food: On your own ( of course kopi kow & biscuits provided).. there are talks that someone will sponsor the lamb barbeque..
Any donation in any form are welcome.

On 15/6/2008, there will be sembahyang Jemaah Maghrib & Isyak and Tahlil before continue DX. Please bring yr own sejadah, kain, anything else..

Station Master: 9M2JEN, 9M2ONE
Project Manager: 9W2YR
Others: 9W2BDZ, 9W2MSG, 9W2DNO, 9W2YDP, 9W2BCT, 9W2RES, 9W2EEE, SWL Akie

- All participants are required to register themself & obtain the ID Tag at the entrance. ID Tag to be wear at all time.
- There will be TV3 shooting during the event.
- Please observe the rules & regulation. This is restricted area. Do not trespass the "No Entry Area".
- Jangan berkelakuan sumbang, nanti time tido kena angkat ke kubur cina di bawah tu.. (joking..hehe)
-
Come & experience DXing with far station around the globe...

Kelas Persediaan RAE 01/2009 - 20/6/2009

Kelas Persediaan RAE 01/2009

Anjuran : ASTRA Kawasan Tengah
Tempat : Pusat Sumber Pendidikan JAIS, Kg. Jawa, Klang Selangor D.E
Tarikh : 6 - 7 Jun 2009 (Sabtu & Ahad).
Masa : 0830 am - 0530 pm
Bayaran Dewasa : RM 20
Percuma : Peserta berusia bawah 17 Tahun & Peserta berusia 60 tahun keatas.
** Bayaran adalah untuk mengisi tabung repeater**

Tenaga Pengajar

9M2AGC Ahmad Azlan (Pensyarah Fakulti Kejuruteraan Elektrik Komunikasi - Politeknik Shah Alam)

9W2JEN Saiful Firdaus (Pensyarah Fakulti Kejuruteraan Elektrik Kuasa - UiTM Shah Alam)

** Nota Kelas diberikan percuma kepada 20 peserta terawal.**
** Makanan tidak disediakan**

Fasiliti Lain - Bilik Hawa Dingin, Projector, Surau & Kemudahan asas lain disediakan.

** Untuk peserta yang memerlukan penginapan, kemudahan disediakan dgn bayaran yg minimum oleh JAIS.
Kepada yang berminat, sila hubungi rakan-rakan dibwh:
1) 9W2JEN Saiful Firdaus - 012 506 2958
2) 9W2BDZ Mohd Fadzlee - 012 616 8183
3) 9W2MSG Mohd Suhaimi - 016 385 9795
4) 9W2GTR Mohd Faizal - 012 310 9869

MUZAKKARAH ASTRA TENGAH 2009/2010

Tempat: Kompleks Rakan Muda, Bukit Kiara
Masa: 2:00pm
Tarikh: 25.4.2009

Dijemput semua ahli ASTRA dan bukan ahli, rakan2 amatur dan komersial, penggemar radio komunikasi bersama menjayakan program di atas.

Pendaftaran keahlian juga disediakan..

Agenda:

1)Perasmian
2)Pembentangan Aktiviti Lepas
3)Mesyuarat - Minutes, Financial, Perlantikan Baru
4)Jamuan Ringan

Pertanyaan lanjut: 9w2mit - Maz

HOW HAM RADIO WORKS - PART 2 - 17/4/2009

Ham Radio Activities

Although a ham radio does broadcast in all directions, hams generally do not use their radios in a broadcast kind of way as a disk jockey would at a radio station. In normal AM or FM radio, one disk jockey transmits and thousands of people listen. Hams, on the other hand, conduct two-way conversations, often with another ham or with a group of hams in an informal roundtable. The roundtable of hams may be in the same town, county, state, country or continent or may consist of a mix of countries, depending on the frequency and the time of the day. Hams also participate in networks, often called nets, at predetermined times and frequencies to exchange third-party messages. In the case of disasters, hams exchange health and welfare information with other hams. Some hams use radioteletype, (RTTY) with computer screens replacing the noisy teletype machines of the past.

Computer-assisted radioteletype

Many hams get their start on VHF FM, using battery-operated hand-held transceivers set to transmit on one frequency and receive on another frequency. They use FM repeaters, set up and supported by local radio clubs. These repeaters borrow antenna space from TV-station-tower owners on top of mountains and high buildings to receive and re-broadcast signals to extend the range.

When deadly floods struck central and southern Texas in mid-October 1998, amateur radio operators from four states volunteered their time. Susan Manor, NF0T, is shown helping with communications at the New Braunfels Red Cross office.

The FM repeater receives one signal at a time and simultaneously rebroadcasts it on another frequency using many more watts of power than available from a small hand-held radio. This extends the range of the hand-held radio from a few miles to tens or hundreds of miles! The whole country has these repeaters! (Listen to one with a radio scanner to learn a lot about ham radio.) When a ham is traveling, he or she can find a repeater to use (great for tips on local restaurants), and carry on a nice, static-free, FM-radio-quality conversation via a radio that fits in the shirt pocket or purse. Linked repeaters allow fun wireless communications across an entire state with a hand-held radio.

Repeaters use common transmit and receive frequency pairs. The frequency pairs in use are informally assigned by groups of hams so that any frequency pair in use is far enough from another repeater so as not to cause unwanted interference.

Amateur radio satellites are a cutting-edge use of technology in amateur radio. Radio amateurs use their hand-held radios to communicate through an amateur radio satellite when the satellite is overhead. A current British satellite has a receiver (uplink) at 145.975 MHz and simultaneously rebroadcasts (downlink) at 435.070 MHz for one station at a time, as a repeater.

Natural disasters like hurricanes or tornadoes disrupt normal telephone and cell phone systems. Ham radio operators pitch in to help with emergency communications, and you will often hear about them on news reports.

On Space Shuttle missions, each member of the crew usually has an amateur radio operator's license. During breaks, astronauts hold their 1- to 5-watt VHF FM hand-held radios up to the shuttle window and chat with other hams for a few minutes, often at schools while the shuttle is in an orbit overhead! VHF transmissions have a limit to line-of-sight communications and normally do not travel over the horizon, so a conversation is limited to the time when the shuttle is overhead. The space station MIR used 145.985 MHz for similar conversations. Future ham radio efforts in space will focus on the use of amateur radio within the International Space Station (ARISS) project.

Ham Radio Equipment

A typical ham radio is a transmitter and a receiver, usually purchased as one unit, called a transceiver. Newer transceiver models often have semi-complicated controls and menu systems that may take some reading of the manual. You may be able to find an older transceiver with controls that are easier to use as a beginner, having the usual analog controls.

Vintage tube-type short-wave receiver

Hand-held transceivers have their own antennas. Many hams choose to do most of their operating from their automobile during commute times, using a magnetic mount antenna connected to an under-dash transceiver or a hand-held radio.

Ham radio station in automobile

Power Output
Depending on the size (hand-held or desktop), power can be from a few milliwatts to 1,500 watts. Many new hams are graduates from citizens band (CB) radio. Unlike the 5-watt limit on CB, hams can use quite a bit more power (1,500 watts).

The ham radio can fit in your shirt pocket, take up half of an attic or garage, sit on a desk next to the computer or go into a car. Right now, during the current sunspot cycle, it is possible to talk around the world during daylight hours running just a few watts of power. This particular type of radio-wave propagation is in the 28-MHz band (commonly called the 10-meter band) thanks to short-wave propagation (300 divided by the frequency in MHz is a quick way to convert to "meters").

Antennas

Little whip antennas, wire antennas in trees, and antennas atop a tower are all used, depending on the frequency in use. Lower frequencies have longer wavelengths. Longer wavelengths need larger antennas. The same antennas (used to transmit and receive) can be small, portable, put in trees or on the trunk of a car.

Short-wave antenna

The common 146-MHz (2-meter) antenna is a 19-inch quarter-wave whip. A wavelength at 146 MHz is approximately 2 (300 divided by 146) meters, and a quarter wave of 2 meters is about 19 inches (50 cm). Hams enjoy the fun of experimenting with various types of antennas. Some antennas are made of wire strung between trees. Be sure to use lightning protection for outside antennas!

Hams, including the writer of this article, have communicated with other hams using the following types of antennas with antenna tuners:

• Metal window screens in upper floors of hotels and motels
• Aluminum extension ladders, insulated from the ground, leaning against a house (the lower the frequency, the longer the ladder)
• Soldered-together rain gutters and downspouts
• Flat copper "burglar-tape" hidden behind wallpapered walls
• Extended "Slinky" toys supported by a rope through the middle, in an attic
• Camera-tripod-supported whip antenna
• Disguised flagpoles fed with buried coaxial cable
• Fine wires cast with a fishing rod between dormitory buildings

What keeps ham operators from transmitting on the same frequency?
Many hams can be on the same frequency, but it depends on the propagation factors. VHF and UHF are line-of-sight, so many hams can be on the same frequency in one state. On short-wave bands, radios have variable frequency tuning to allow moving your transmitted signal (in very small increments) in between two other transmitting stations. Hams often do a lot more listening than transmitting. Often, they listen for another ham that identifies the station as being in a sought-after county, state, or country.

This LCD on a modern transceiver is displaying the spectrum of nearby stations. The band-scope at the bottom helps ham operators find signals.

Hams collect confirmations of contacts using QSL cards. Hams collect the QSL cards and receive awards for contacting so many countries on certain frequency bands. VHF and UHF hand-held radios typically use channeled communications, using selectable fixed frequencies.

HOW HAM RADIO WORKS - PART 1 - 17/4/2009

How Ham Radio Works

by Brown, Gary. "How Ham Radio Works." 01 April 2000. HowStuffWorks.com. 16 April 2009.

Inside this Article

1. Introduction to How Ham Radio Works
2. Why would I get into ham radio?
3. Frequencies and Transmitting Modes

4. Ham Radio Activities
5. License Requirements
6. Ham Radio Equipment
7. See more »

   7. Antennas
   8. Hamfests
   9. Getting Started with Ham Radio
   10. Lots More Information
   11. See all Radio articles

Radio Image Gallery

Ham radio lets people talk across the globe, wirelessly and inexpensively. See more radio pictures.

A teen in Florida makes friends over the airwaves with a ham in Germany. An aircraft engineer in Washington participates in an annual contest and exchanges call signs with hams in 100 countries during a single weekend. In North Carolina, volunteers pass health and welfare messages in the aftermath of a hurricane.

This mix of fun, public service, friendship and convenience is the main feature of amateur radio. The true origin of the term "ham" seems to have been lost, but there are several theories. It may simply be a shortcut way of saying the first syllable of amateur radio, or it may have originally been used as an insult. Hams start out in amateur radio for many reasons, but they all have in common a basic knowledge of radio technology, regulations and operating principles.

Tune In How Radio Works Radio Spectrum Discovery.com: Radio Telescopes

­

­ Ham radio can be very portable and affordable. In this article, we will look at ham radio and show you how to get started in this wireless world!

Why would I get into ham radio?

Ham radio is for anyone who likes to communicate with others via wireless technology. It is also for anyone who enjoys experimentation. Licensed amateur radio operators communicate with each other in nearby places, across the country, around the world or even with astronauts in outer space!

Amateur radio is a worldwide group of people who communicate with each other over a wide frequency spectrum using many different types of wireless transmitting modes.

Often, younger hams get a chance to meet other hams of various ages and professions. For example, Kid's Day is an annual event that encourages young people to get on the air, perhaps with a family member or a neighbor who is a licensed amateur radio operator. The frequent networking often helps teens when they are making career or education choices and wish to get some advice (from professionals in many technical fields) that maybe mom, dad or the guidance counselor may not be able to give.

Today, there are more than 2.5 million around the world.

Frequencies and Transmitting Modes

Hams use a variety of frequencies for communications. Non-hams can "listen in" via their own receivers or radio scanners. Hams are able to use many frequency bands across the radio spectrum -- these frequencies are allocated by the FCC for amateur use. Hams may operate from just above the AM broadcast band to the microwave region, in the gigahertz range. Many ham bands are found in the frequency range that goes from above the AM radio band (1.6 MHz) to just above the citizens band (27 MHz). During daylight, 15 to 27 MHz is a good band for long-distance communications. At night, the band from 1.6 to 15 MHz is good for long-distance communications. These bands are often referred to historically as short-wave bands (as in "short-wave radio"). Unlike frequencies used by FM radio stations and TV stations, which are line-of-sight and therefore limited to 40 or 50 miles, short-waves "bounce" off the ionosphere from the transmitter to the receiver's antenna. The higher the frequency is, the "shorter" the wavelength is.

Some ham radio operators use the very reliable Morse code, while others use voice. Morse code signals (beeps) often get through when voice transmissions cannot. There are also very many digital modes as well, and hams use radio modems to communicate in various networks.

HOW RADIO WORK - Part 3 - 17/4/2009

The Simplest AM Receiver

In the case of a strong AM signal, it turns out that you can create a simple radio receiver with just two parts and some wire! The process is extremely simple -- here's what you need:

• A diode - You can get a diode for about $1 at Radio Shack. Part number 276-1123 will do.
• Two pieces of wire - You'll need about 20 to 30 feet (15 to 20 meters) of wire. Radio Shack part number 278-1224 is great, but any wire will do.
• A small metal stake that you can drive into the ground (or, if the transmitter has a guard rail or metal fence nearby, you can use that)
• A crystal earphone - Unfortunately, Radio Shack does not sell one. However, Radio Shack does sell a Crystal Radio Kit (part number 28-178) that contains the earphone, diode, wire and a tuner (which means that you don't need to stand right next to the transmitter for this to work), all for $10.

You now need to find and be near an AM radio station's transmitting tower (within a mile/1.6 km or so) for this to work. Here's what you do:

• Drive the stake into the ground, or find a convenient metal fence post. Strip the insulation off the end of a 10-foot (3-meter) piece of wire and wrap it around the stake/post five or 10 times to get a good solid connection. This is the ground wire.

• Attach the diode to the other end of the ground wire.

• Take another piece of wire, 10 to 20 feet long (3 to 6 meters), and connect one end of it to the other end of the diode. This wire is your antenna. Lay it out on the ground, or hang it in a tree, but make sure the bare end does not touch the ground.

• Connect the two leads from the earplug to either end of the diode, like this:

Now if you put the earplug in your ear, you will hear the radio station -- that is the simplest possible radio receiver! This super-simple project will not work if you are very far from the station, but it does demonstrate how simple a radio receiver can be.

Here's how it works. Your wire antenna is receiving all sorts of radio signals, but because you are so close to a particular transmitter it doesn't really matter. The nearby signal overwhelms everything else by a factor of millions. Because you are so close to the transmitter, the antenna is also receiving lots of energy -- enough to drive an earphone! Therefore, you don't need a tuner or batteries or anything else. The diode acts as a detector for the AM signal as described in the previous section. So you can hear the station despite the lack of a tuner and an amplifier!

The Crystal Radio Kit that Radio Shack sells (28-178) contains two extra parts: an inductor and a capacitor. These two parts create a tuner that gives the radio extra range. See How Oscillators Work for details.

Antenna Basics

You have probably noticed that almost every radio you see (like your cell phone, the radio in your car, etc.) has an antenna. Antennas come in all shapes and sizes, depending on the frequency the antenna is trying to receive. The antenna can be anything from a long, stiff wire (as in the AM/FM radio antennas on most cars) to something as bizarre as a satellite dish. Radio transmitters also use extremely tall antenna towers to transmit their signals.

The idea behind an antenna in a radio transmitter is to launch the radio waves into space. In a receiver, the idea is to pick up as much of the transmitter's power as possible and supply it to the tuner. For satellites that are millions of miles away, NASA uses huge dish antennas up to 200 feet (60 meters ) in diameter!

The size of an optimum radio antenna is related to the frequency of the signal that the antenna is trying to transmit or receive. The reason for this relationship has to do with the speed of light, and the distance electrons can travel as a result. The speed of light is 186,000 miles per second (300,000 kilometers per second). On the next page, we'll use this number to calculate a real-life antenna size.

Antenna: Real-life Examples

Let's say that you are trying to build a radio tower for radio station 680 AM. It is transmitting a sine wave with a frequency of 680,000 hertz. In one cycle of the sine wave, the transmitter is going to move electrons in the antenna in one direction, switch and pull them back, switch and push them out and switch and move them back again. In other words, the electrons will change direction four times during one cycle of the sine wave. If the transmitter is running at 680,000 hertz, that means that every cycle completes in (1/680,000) 0.00000147 seconds. One quarter of that is 0.0000003675 seconds. At the speed of light, electrons can travel 0.0684 miles (0.11 km) in 0.0000003675 seconds. That means the optimal antenna size for the transmitter at 680,000 hertz is about 361 feet (110 meters). So AM radio stations need very tall towers. For a cell phone working at 900,000,000 (900 MHz), on the other hand, the optimum antenna size is about 8.3 cm or 3 inches. This is why cell phones can have such short antennas.

You might have noticed that the AM radio antenna in your car is not 300 feet long -- it is only a couple of feet long. If you made the antenna longer it would receive better, but AM stations are so strong in cities that it doesn't really matter if your antenna is the optimal length.

You might wonder why, when a radio transmitter transmits something, radio waves want to propagate through space away from the antenna at the speed of light. Why can radio waves travel millions of miles? Why doesn't the antenna just have a magnetic field around it, close to the antenna, as you see with a wire attached to a battery? One simple way to think about it is this: When current enters the antenna, it does create a magnetic field around the antenna. We have also seen that the magnetic field will create an electric field (voltage and current) in another wire placed close to the transmitter. It turns out that, in space, the magnetic field created by the antenna induces an electric field in space. This electric field in turn induces another magnetic field in space, which induces another electric field, which induces another magnetic field, and so on. These electric and magnetic fields (electromagnetic fields) induce each other in space at the speed of light, traveling outward away from the antenna.

For more information on radio and related topics, check out the links on the next page.