Primer for Ham radio part one

by M.D. Creekmore on October 16, 2012 · 8 comments

This guest post is by Michael C and entry in our non-fiction writing contest .

(This is part one of a four-part series - intro, history, AM, Carrier)

There are less than 4 million active ham radio operators in the USA – about 1% of the population. I use my ham radio mainly to contact a friend about ten miles away. I don’t get involved with the contests or DXpeditions - just wanted a better radio then the CB radio. Ham radio is about contact between two people at a distance – sometimes great distance like around the world. I am going to try to explain Ham radio above the “refer to a book” level for those considering ham radio as a means of communication. A slight history of Radio is in order to bring those who don’t know much about “radio” up to speed.

A man by the name of Hertz discovered electromagnetic waves could move through the air and effect a similar shaped “receiver”. The first real radio was made by someone named Marconi. Radio was born but not before a man by the name of Tesla figured out that tuning different frequencies were possible. Amateur radio operators were some of the first people to take advantage of the “wide open airwaves” with the first radios built.

The radios were cheap to create – a crystal set only required finding a good crystal, a coil of wire and an earphone. The Edison light lead the way for the radio tube which allowed the “amplification” of any signal. The incoming signal from the antenna is amplified and then the audio signal is amplified. A small tube receiver can amplify signals hundreds of times – allowing weak/far away radio to be heard. So, for a few bucks more you could have a pretty good radio that played through a speaker. The transistor was capable of amplifying the signal thousands of times and saving some battery power.

Even though Morse code is the easiest signal to transmit, it is not vocal and I will confine my article to verbal transmission. Audio signals are the “real time” type of communication needing constant update. AM, SSB & FM transmission modes were developed for audio. It would be criminal to not mention ARRL (Amateur Radio Relay League) an organization that has supported ham radio operators almost since the beginning. For those who have never operated a radio – just press the key on the microphone and talk, then release the key and listen for a response.

AM

The first and easiest radio mode is the AM (Amplitude Modulation) radio. CB radio is AM radio transmission based. The concept is simple – put a sound wave inside (or outside) of a “carrier” wave. The sound wave is audio frequency, for the early microphones about 300 to 2000 Hertz. The carrier wave is a mirrored sine wave that cycles at the “air wave” frequency. The sound wave is simply “fitted” into a carrier wave shape.

Although the sound wave “edges” the carrier, if there were no sound – the carrier would still be created and transmitted. This was called an empty carrier or in CB slang a “dead key”. This is used to “drown” out other CB’ers. I mention mirrored sine wave – the “electromagnetic” field created (by the antenna) has a north pole and a south pole. Both of these poles (amplified signal) must be beamed out by the antenna. The frequency of “AM Radio” is around 525 to 1710 (1.71 MHz) Kilo cycles and if we care about ham radio frequencies then the first ham frequency begins at 2 MHz (2000 Kilo cycles) and extends to 4 MHz. AM dominates the HF (High Frequency) spectrum up to about 29.0 MHz where FM is finally available. It is the age-old problem for FM – not enough band width to support the mode.

This contest will end on December 16 2012 – prizes include:

  • First Place winner will receive a Go Berkey Kit valued at $150.
  • Second Place: $100 Cash.
  • Third Place: $50 Cash.

Well what are you waiting for – email your entries today. But please read the rules first… Yes

8 comments

JP in MT October 16, 2012 at 10:15 am

Love it!

I went through electronic school with the Army, in 1976! Forgot most of what they threw at us, so this is a great refresher.

Comms is a weak area for us. So any and all info is welcome. I’d rather listen to someone who knows what’s going on, than make all those mistakes, especially with equipment, and waste money.

Tactical G-Ma October 16, 2012 at 3:14 pm

Thank goodness we don’t have to be an engineer to use a radio. I clearly understood push button to talk and release to listen. No matter how many times I am told about it, it is still PFM to me!

OhioPrepper October 16, 2012 at 3:40 pm

Michael,
You state that “AM dominates the HF … spectrum up to about 29.0 MHz …” but I rarely if ever encounter AM stations anywhere in the ham bands, so I hope you will be adding a discussion of sidebands and their efficiencies relative to AM.

michael c October 17, 2012 at 8:49 am

Stay tuned…

Nancy V October 16, 2012 at 4:10 pm

Great article, am looking forward to the rest of your articles regarding Ham Radio. My interests lay with mobile units, handhelds, etc., with solar recharging capabilities so I can take communications with me. I have my technician’s license and am working on my General License. I use a Kenwood TH-F6A 144/220/440 MHz FM TriBander. The radio comes with its own standard recharger for the supplied Li-ion Battery, has an antenna, strap and manual. I have 2 backup battery packs and keep them charged via solar power so I can switch them out and stay on the air for a period of time. The audio signal range is about 5-10 miles depending, and CCW is further. It is a good starter handheld and so far has been dependable for me. I would be most interested in hearing about your antennas and power supplies.

michael c October 17, 2012 at 9:43 am

Most of my antennas are store bought multi-band (2/440 or 2/6meter or 2/220) roof mounted units. I have a couple of directional antennas that also receive dual bands. I have standard antennas on my hand-held radios. The only antenna that I made was a “hyper directional” 2 meter that needed angle adjustments in addition to rotation to hit a spot. My philosophy on antennas is buy the regular ones at the store – build the one you can’t buy.

As for the power supply – sunlight charges my battery bank and the radios tap off of that. All of my radios run on 12 volts. I have a 60 amp DC rated breaker to protect the electronics yet allow 50 Watts to transmit from the mobile radio.

MountainSurvivor October 16, 2012 at 6:28 pm

Do not forget that every person has to pass their test before they can enter the air waves or it could be bad news. My dad used to operate HAM every night and he once conversed with, I believe it was, Marlon Brando. And, my dad knew his dashes from his dots, never seemed to miss a beat. Anyway, good article and looking forward to more of them.

thatAway October 17, 2012 at 8:29 am

I agree with O.P. Am is rarely used on HF bands.
Occasionally I hear it when people are using old restored Am rigs on the H.F. bands And a few rare Am clubs. And they usually are on 160m or 75/80m. But there are still some allocated frequencies used as am calling frequencies.. But with the advent of all the other modes it is inefficient mode to use in most cases. But a good start to your series..
lets see where yo go with this.
73
thatAway

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