Posted on March 15th, 2009 No comments
In amateur radio, QRP operation means transmitting at reduced power levels. The term QRP comes from the Q code used in radio communications, where “QRP” and “QRP?” are used to request, “Reduce power” and ask “Should I reduce power?“. The opposite of QRP is QRO, or high-power operation “Increase Power” or “Should I increase power“.
There is not a default standard what QRP is. Many operators consider that they are in QRP operation when the power output of their transceiver is 5 Watts (on CW or AM operation) or 10 Watts on SSB operation. Others consider QRP operation every transmission up to 2 or even 1 Watt. QRP equipment is lightweight and often radio amateurs combine QRP with portable operations (/p in the call signs).
Every modern transceiver has an adjustable RF power output. This means that every commercial HF (or VHF) transceiver can operate as a QRP one. If the operator wishes to transmit in QRP levels, he can adjust the RF power of the transmitter to, lets say 2 or 5 Watts. In the market there are many QRP level only transceivers. Some of the most known are Elecraft K1 and K2, but the real pleasure in QRP activity is the several home-made qrp transmitter kits. A radio amateur can built one, with very easy to find parts, at a cost of some 4-5 Euro !!! In fact, there are many articles and sources of information that show us what a transmitter like this can do: There are logged QRP QSO’s between radio amateurs that are in different continents.
Operating QRP tranceivers
A significant bonus of QRP activity is that every QRP transceiver has a very low power consumption. This means that can operate for many hours with a small battery. Another bonus is the lightweight of the equipment and the simplicity of the design (especially in CW qrp transceivers).
Posted on March 2nd, 2009 No comments
Morse code is a method to transmit information. The letters of the words and the numbers are transmited with sounds that represent dots or dashes from a table of correspondent symbols.
History & uses of Morse code
The Morse code was invented by Samuel Morse in 1830 and was used in first place for the wired land telegraph communications.
After Marconi’s experiments about wireless transmissions, it become the default wireless transmission method.
Historically speaking, the Morse code was used by many communication services, like telegraphy, maritime communications, aviation, military communications and of course by the radio amateurs, who continue to use the code. There are many reports on how the use of Morse code was helped during emergency situations, etc.
This is the CW ( = continuous wave) transmission mode. In this mode the radio amateur does not communicate using voice. He is using a special switch (the key) that allow him to send short or long sounds [dots or dashes] via his radio. The transmission speed is count using “Words per Minute, W.P.M.” or “Characters per Minute, C.P.M“. Typical speeds are around 20 W.P.M. (for manual sending, not automated stations or computer CW software).
The knowledge of Morse code, is optional some years ago, after some decisions or instructions of international radio amateur unions and organizations. However, in most countries, the knowledge of the Morse code, gives the ability to the radio amateur to have the full privileges on all bands, especially in HF bands.
The code – Letters & Numbers in Morse Symbols
The complete correspondence of the letters and the numbers with the symbols of the Morse code (dots and dashes), is like the following table:
Other information – Morse code transmission rules
- The duration of a dash is exactly the same like three (3) dots duration
- The time of the space between the sounds of a single letter is exactly the same like one (1) dot’s duration
- The time of the space between letters is the same like three (3) dots
- The time of the space between words is the same like seven (7) dots
Advantages of Morse (CW mode) in telecommunications
- The communication is achieved using a narrow bandwidth – CW communications use some 100-150 Hz of bandwitdth, unlike the SBB voice communications that use at least 2.400 Hz (or 2,4 Khz)
- There is “room” for more stations in the same frequency (using “narrow” bandwidth filters in the receiver)
- Extended coverage with the same power output
- Simple circuits in the tranceivers
- Convenient for QRP transmissions (low power)