Thursday, April 8, 2010

Back on the blog....


I have been out and about - spent considerable time away fom my computer - and out of reach of internet.  Also with very little time to do my Ham radio -  However I will hopefully be able to come more to the point and keep the ether going again.

April 2010

Sunday, December 31, 2006

Using shortwave radio to send E-mail?

To be in contact with loved ones and colleages has always been the goal of most people exept those who want to dissappear. Winlink 2000 has used the technology developed by the group of German amateurs to setup a system that has really become the life line of many, weather you are a sailor on the high seas, or a missionary in the sticks out in the bush in Africa of South America, or just touring your beautiful country in a motorhome there is now never an excuse to be out of reach if you are a radio amateur.

The system uses HF (also known as shortwave) radio to connect you to a remote mail server and download / upload e-mail to and from anybody anywhere in the world. The funny thing these days are that the third world countries probably offer you internet cafe's but more often than not they charge you more than an arm and a leg for the sub-standard service and even expose you to all sorts of virusses and trojan horses that could steal your identity. This is not the case with Winlink 2000.

To read more on this please visit .


Jan 2007

Thursday, December 21, 2006

Amateur Weak Signal communications

Weak signal communications refer to communications between two stations where the stations are not necessarily able to hear the communication signals with the human ear.

Decoding weak signal amateur radio with the aid of computers.

The signals are usually decoded with software in a computer with the help of what is known as digital signal processing via a sound card. How did the idea of weak signal communications develop in Amateur radio? Well it is well known that the strength of a signal at the receiver mainly depends on the size of the antenna of the receiving station. The power of the transmission at the transmitting station and the distance between the two stations and normally the "quality" of the space between them. If any of these are in any way less than favorable the signal will probably not be "heard" by the receiving station. But the theory states that the signal is not gone it is still somewhere shaded by the noise caused by other electrical transmissions that cause the hiss we normally hear.

Efforts to bring weak signals out of oblivion:

So a group of radio amateurs decided that there had to be a way to get the weak signal shaded by the noise processed by digital means so that the human ear can hear it or the computer can decode it. All sorts of tricks were designed like:

  • To induce a pseudo signal that will remove the noise because it is out of phase - although crude it worked well and many a marginal signal was drawn out of the noise in this way.
  • Another attempt was to shift the freq of the oscillator of the intermediate frequency and get the intermediate frequency out of the pass band of the noise. This sounds very technical but it actually meant that the noise was moved away from the signal.
  • When computer processing of sound and audio signals was introduced it opened a whole new world of possibilities - and that is where we are today.
Even bouncing signals off the moon over 350 000 km from earth became possible.

Armed with the right equipment and computer the amateur radio operator can literally use an antenna - point it at the moon and "listen" to or at least decode another operator’s signal coming back off the moon where the moon is used purely as a reflector. The first contact like this was done between a station on the east coast of America and one on the west coast on a frequency one would usually require both stations to be able to "see" each other in a configuration that is known as "line of sight".

Not only boucing signals off the moon but also meteor showers.

Recently amateurs have started to even bounce signals of meteor showers. Very few people realize that there are a lot of meteors that enter the atmosphere daily and it was discovered that with careful planning and good equipment and digital signal processing with the aid of a decent computer. The author personally holds the South African record with meteor scatter contacts of over 1800 km with fellow Amateurs on two of the frequencies that usually require line of sight propagation. He has also done several contacts via the moon with stations all over the world including contacts with stations from every continent on one particular band.

I truely believe that our imagination is our limitation in weak signal communications by amateur radio!

To read more about these and other weak signal communication techniques:
EME for Africa
Sam in Russia
Dave in USA
Dan in Switzerland

Written by JD
South Africa
22 December 2006

Amateur Radio Data Communication

Amateur Radio Data Communication was really the start of what we today know as WIFI, GPRS and 3G.

Where does amateur radio data communication come from?

Since the earliest days of radio communication - Marconi and his spark transmitter - the first basic communication techniques required operators to transmit alphanumeric characters in an audio form that was not spoken. The first development was of the Morse code as the means of transmitting alphanumeric data. Over the years the developments was that ham operators devised procedures and technology to send and receive these Morse code signals know in ham radio as CW (an acronym for Continuous Wave). The signals are done by keying a continuous wave on and off in pure CW. The receiver then hear it as a signal on his side and by careful determination and later by using computer sound card technology the signals are decoded.

How did the true data modes of today develop?

Now with all these attempts to get the information sent faster and faster the developers devised other ways that pure on and of switching of a carrier wave and the process of building more and more complex modulation developed to a point where at first the signal was coded by on-off keying of a signal at a rate of approximately 5 to 65 words per minute to an effective data rate of several megabits per second on the latest microwave links. It was all a matter of refining the traditional systems to near perfect and then changing some small aspect to get a new mode to refine.

How does data communication work?

There are basically 2 basic modes of data transmission Analogue that means a piece of data like this page on the web is changed in a modem (where MOD- in modem means modulator) from a digital electronic signal on a computer disk to a analogue audible signal that is transmitted via a normal voice channel on either a telephone line or via a radio link. These have severe penalties due to attenuation (also known as the degradation of the signal). The modem will often use different tones for different digital signals. The normal limit for analogue modems on either radio or telephone lines is about 57 kbps. At the receiver the sound signal that was modulated at the origin is demodulated to become a digital signal again. The DEM in modem is for demodulator.

Recent developments in digital technology brought the data rates on digital links like GPRS, 3G and WIFI up to several gigabits.

Data communications in less than favourable conditions.

What often happens is that when the 1st world are working at improving their systems in 2nd and 3rd world countries they need to use the technologies that is often seen as redundant in the 1st world except in emergencies. The recent Tsunami (2 years ago in South East Asia), and the Hurricane that hit New Orleans took out all the state of the art communications and fixed installations. The area was literally cut off from the world in terms of communications and the data communications was only possible via satellite or short wave radio - and guess what - Radio Amateurs had the means to provide data communications in cases where the satellite was over stressed due to all the traffic.

In Africa internet connectivity is still seen as a luxury and very expensive. Email is virtually impossible due to poor telephone links so what remains? Short wave radio.

What does the future hold for us on data communication front?

The new developments in this is probably going to change the way we live for ever - internet is already easy to get to via your mobile phone - and that in itself is not even the end. Next is probably going to be wrist watches or designer glasses with a receiver built into the frame and something of a Heads-up-Display on the lenses?

Personally I enjoy playing with radio data communication techniques.

Links with further info about radio data communication:

Written by JD
22 December 2006
South Africa

Amateur Radio Equipment - Where to get it?

Amateur radio equipment is often tough to get your hands on. But don't dispair I hope to help you in the next few paragraphs to know how to get good amateur radio equipment at reasonable prices.

New Amateur Radio Equipment.

There are several well known dealerships of Ham Radio Equipment who have advertising on the internet. But you will probably want to meet the dealer and build a relationship with them or even run the radio in a test in the shop. This is unfortunately not always possible if you buy online. In this case it is worthwhile to find a ham close to you that is already using the same type of radio that you intend to purchase. Arrange to visit and use the radio hands on. You can also get some first hand feedback from someone that has used the radio. Also read other reviews of the model you intend to purchase. In other words do your homework! Once you know what you want start shopping for the best price with the best service and guarantee.

Used Amateur Radio Equipment

When shopping for Used Amateur Radio Equipment there are many loopholes to lookout for. The most problematic is so-called DOA (Dead On Arrival) radios. It is an old trick of Ham's who have problems with their equipment to try and sell it to an unsuspecting buyer who then has to pay for the expensive repairs. So in every instance it is good to have technical test of the equipment done? This can be done by a independent friend you trust that could visit the seller and check the radio - or you can do it yourself. Often with e-Bay and other online advertisers the world is becoming a smaller place where it is not funny to find Australian Hams selling to Hams in the USA or where ever.... So get someone to check the equipment that is working before parting with your cash.

Another problem with used equipment is so-called guys/girls that have fingers that like to fiddle with adjustments that are normally reserved for people who are qualified technicians. The radio might not be DOA (dead) but chances are that the radio in such a case will probably not work properly - off frequency, deaf and under powered.

The last problem one might encounter is that the amateur radio equipment might have been stolen. This is especially true if you are buying from a non amateur. If you suspect something amiss post a message on one of the major blogs and enquire if anybody has lost a similar radio and ask them to post the serial number - don't put the number you have to prevent any uncertainty.

I hope you can get good equipment at reasonable prices.

Written by JD
South Africa
21 December 2006

Ham Radio - How to get started in Amateur Radio?

Well if you want to get started with Ham Radio there are a few easy steps:

Decide to be come a Radio Ham:

First of all you need to decide to do it. Yo have to make sure you want to do it as it is going to take a real effort from you to become a Radio Amateur. It is time and effort you want to put to good use! It will take commitment and hard work to study the theory and do the examination. It will probably mean that you will have to be assisted by fellow hams but it will be worth the while, as you will not only learn the theory and technicalities but also the ethos of being a Ham.

Get in touch with local Amateurs.

Next you will probably need to get in touch with your local club or association. Do a search of the web with the words "Radio Amateur"+(name of your city or town or country). Chances are that you will get the required information on how the process would work in your country.

Do the amateur radio license training program.

The club or association will also be able to put you in contact with a testing centre close to where you live where you can enroll for the course and get the study material for the Ham Radio Examination. The best way by far is to attend the course or get a computer aided training system.

Do the amateur radio license examination.

Once you are ready to do the exam - do it. Often you will be able to know within a few days if you passed or not. The rest is History . . .

Get the radio amateur license.

If you pass the examination you can apply for the license. Once the application is lodged or approved depending on local regulations - you will probably be allowed to start using equipment on the frequencies your license permit you.

To read more about becoming a radio amateur in your country please follow the link below:
South Africa
United Kingdom

Enjoy becoming a Radio Ham.

Written by JD
South Africa
21 Dec 2006

Ham Radio - what is it?

Ham Radio is essentially a service to the community where individuals who have used their time, knowledge and equipment to serve the community in a variety of ways but usually by providing communication services when the other services have failed or just for the fun of it. Lets look at these one by one:

Ham radio operators offer their time!
First of all to be a radio ham one has to go through a process by which you get licensed by the authorities in the country you live. This procedure is usually also agreed to by international treaty in the International Telecommunications Union to which large number of countries are members and signatories. The time the ham has to spend learning the theory and legal stuff is a sacrifice but is surely rewarded later.

The licensing procedure usually involves a technical examination by a representative body in which the candidate is required to pass 2 sections of the exam the one being theory of radio physics and the other usually is some sort of knowledge of the local radio regulations. Once this is completed successfully the operator sometimes has to do and pass a practical demonstration where he/she shows himself or herself to be a competent operator of the radio equipment on the frequencies and at the power levels that he/she is allowed to use.

Ham operators offer their knowledge!

Wonderful because when all this is done the world opens up. When conditions are good and equipment is properly set up the operator can literally switch the radio on and at the turn of the button on the radio get in touch with the whole wide world. It is such a feeling of accomplishment to experience installing a home made antenna connecting it to a length of antenna cable and attaching it to the radio. When all this is done and you hear that station on the other side of the world on short wave or even on the other side of town with the very high frequencies.

The knowledge that one has as a ham operator means that when that is applied properly it leads to being able to select the right frequency band for the time of day and the distance as well as the varying conditions to have successful communications between two or more points.

Yes some people might say why do it with radio when we have the internet and the chat rooms and voip? Well the truth of the matter is that all that is available because of the interest of experimenting amateur radio operators through the years. May a new development like wifi etc has come the road where the first prototype was first tested by amateur operators somewhere.

Apart from that we have to look at the problems faced by the emergency services during times of disaster like tsunami's, earthquakes, hurricanes and wild fires. The agencies are reliant on effective communications in such times - more often than not the telephone systems are either over stressed due to the high call volumes, or rendered completely useless due to damage to the cables. Even cellular communications could be rendered unavailable due to them also relying on the cables from the telephone company to get to the switches and exchanges from the towers you and I connect to. The agencies has their own radio systems and hopefully it will be operational, but limited as not many might have access to the frequencies.

Ham operators use their equipment in service!

The numbers of the people operating in the ham bands with equipment that is often tested in simulation exercises and in less than ideal circumstances often with only emergency power from either batteries or generators where the tests were done to determine abilities.

Over the years the ham radio community has shown that through dedication and with the assistance of fellow hams they could step in and fill the void that might happen in emergencies - while they will thoroughly enjoy the ability afforded to them to get in touch with as many people as possible from as many countries as possible on as many frequencies as possible.

Written by
South Africa