Amateur Radio Association of Lanka

An Introduction to Amateur Radio

What is Amateur Radio

Amateur Radio is a hobby for a community of people who are communicating with each other using a radio transmitter, and a radio receiver. Actually this group of people are called Radio Hams or just Hams! I cannot say how this term is being created, but Amateur Radio operators are identified as such throughout the world. Hams are not only making use just to chat among them using voice, or radio telephony, besides there are number of techniques they use for example, amateur television, Morse code, digital communication, etc, etc. There are number of software programs dedicated to licensed radio hams so that they can communicate with other hams around the world, e.g. Echo link. Ham Radio is a very dedicated hobby and among radio Hams they interchange and discuss technical matters, help each other, self learning matters related to electronics, etc. Radio hams all over the world have served in many disaster situations. Ships in distress have been handled by radio amateurs, therefore I am very proud to mention we have a great hobby. Even in Sri Lanka they have served in many disasters, I remember when Batticalow was flooded the only communication was via ham radio. Not forgetting the last Tsunami the only communication in that situation was possible by Radio communication network established with the assistance of a group of dedicated radio hams establishing contact between down south and Hon. Prime Minister's Office in Colombo. A group of amateur radio operators have gone to the disaster areas carrying their equipments, batteries, antennas and established communications to Colombo and made a great job, rendering assistance to government establishments, especially Social Services Ministry & P.M.'s Office, when telecommunication networks either disrupted or congested for couple of days soon after the Tsunami.

Ham Radio hobby is internationally recognized, and all radio hams are addressed by a call sign. It is identified by one or more letters and numbers with prefixes assigned to the respective Country where the amateur radio operator is domiciled. For example a Ham in Sri Lanka the call sign always start with, 4S. In Great Britain it is G, In Denmark OZ, followed by numbers or letters according to the category of the license, or the countries division. So this permit an operator to recognize the Country of Origin of the ham in the other end. The amateur radio or ham radio is very great medium of radio communication technique that bring communities in the World together, make friends, share knowledge and techniques and lend a hand in any emergency or disaster situation if all other means of communications fail, because radio communication equipment can be operated with low voltage portable power packs(batteries) using mobile antennas.

Nowadays some people will react, would be critical of, why one should go to hassle of using amateur radio techniques when in modern day when cellular phones are the fashion to communicate world wide at any given time. Yes, one must not forget the fact that - all public communication systems can go dead, disconnected in a disaster or in an emergency situation, while mobile amateur radio transceivers with back up power supplies can last until such time, normal communications are restores.

Further, as it did happened so, all public communications network failed or got congested with unlimited traffic in 2004 Tsunami, radio communication network became so useful in that moment of national disaster. Also it is great fun to radiate a signal from your antenna to the other antenna some where in the other end of the World remote station. Today almost all Astronauts carry a ham ticket, ham radio equipments and make themselves available to communicate between International Space Station and Earth with Hams. ISS Amateur radio wing even line up school children to engage in radio communications with ISS in promoting friendship and knowledge in radio communication techniques from far and wide in the Space and Earth.

We hams have our own terminology, or short phrases, using a code called Q code, for easy operation, e.g. QTH is for where you are living. QRM is for disturbances like noise, etc. Internationally the frequency bands are dedicated to radio hams, from Very Low frequency to super high frequency bands. They are not permitted to deviate from the respective band segments allocated to them. So I hope this is all about Amateur Radio in a nut shell.

How to Become a Radio Amateur

Amateur Radio Operators have to qualify in an examination conducted by the TRC - Telecommunication Regulatory Commission of Silence and obtain license for operating / possessing a Radio Station. Any individual above the age of 14 is permitted to appear for Amateur Station Operator License Examination, It takes just two months (say two hours a day training) to become eligible for the examination. One should qualify a simple test conducted in two subjects namely I) Communication Procedure ii) Basic Electronics. Defense clearance, a good police report, etc

Amateur Radio Licenses are also granted to Schools with a special call sign. Once a year a day is reserved for boy scouts and girl guides to communicate to fellow scouts via a licensed ham radio station, it's called Jamboree on the air. We hams invite boy scouts and girl guides home and give them a chance to say hello to other countries scouts and guides. The day is internationally arranged.

Diode probe

I am sure some of our home brewing interested hams may have come across problems, trimming RF circuits. Oscillating or may be the circuit has to be trimmed to a minimum dip, etc, etc. During my old days with Storno (A Danish firm fabricating Radio equipments) I was issued with a simple RF probe to trim there radios. It was a very simple instrument which saved me from lots problems, as well as my private ham experiments at home.

May be some of you have already constructed a simple probe like this and have experience. Any way I thought of writing a small article in our bulletin for the benefit of some interested. It is so simple that one needs, only six components! A suitable enclosure such as an old ball point pen house, a pointed pin or the like. A length of wire. ( A screen cable should be used)

Theory of operation is very simple.

C1..C2..C3..1to 5 nF

D1..D2..OA95 or similar Germanium diode (a matched pair)

R1..4.7 ohms.

This configuration is made so that it's a simple detector to detect both positive and negative half of the RF signal.

The resultant DC voltage will be peak to peak at C2 with respect to the input RF voltage.

Please note the following.

Enclosure has to be of metal.

The multi-meter should be of at least 100,000 ohms per volt. In mile volt scale. (an analog meter is better for this)

This simple circuit can be enclosed insulated from the metal body and the input terminal before C1 can be made to a sharp pin, point contact. This ensures the circuit point to be measured be of good contact. The common ground to be connected to the ground point of the circuit to be measured.

Disclaimer.

Any improvements and comments are welcome; this simple circuit is to be used at the entire will of the constructor. At his own risk!

73s!....4S7LF….Leo