QRP or low power operation has a large and growing band of radio hams who enjoy this aspect of amateur radio. Even many radio amateurs whose licenses enable them to use the full legal power still prefer QRP operation as it gives them a great sense of satisfaction and provides a whole new world of challenges in terms of amateur radio operating as well as building the equipment.
In view of the enjoyment that QRP operation provides a considerable number of radio amateurs only operate QRP, while others may have high power stations, but also operate in a QRP mode at other times to provide another dimension to their amateur radio operation.
What is QRP?
Essentially amateur radio QRP operation can be defined as operating with low power. There are defined limits for these as given below, but in reality QRP often implies more than this. Not only do people operate using QRP, but many people also build their own equipment. Another aspect of QRP is that many people also use wire antennas they have built and erected themselves. All of this gives a real sense of achievement when contacts are made, especially if they are made over long distances.
In view of the fact that signal strengths are lower than those of stations using higher powers, most QRP operation uses Morse, although this is not exclusively the case. Using Morse transmissions enables contacts to be made when it would not be possible using other modes. Nevertheless SSB and other modes are used for QRP operation.
Making ham radio contacts using powers that are considered to be QRP can be particularly rewarding. However, it may not be such a disadvantage as might be first thought. Reducing the power from 400W down to 4W output represents a reduction of 20dB. A figure of 6dB is generally taken to be equivalent to an 'S' point and therefore this power reduction represents a reduction of just over three 'S' points. In other words, if a station running 400W (26dBW) was being received at S9 and it reduced the power to just 4W (6dBW), it would still be copied at around S6. While a QRP station might not be able to operate through many pile-ups, the figures show that it should still be possible to make plenty of contacts. This is proved is reality every day on the amateur bands where many QRP contacts are made.
QRP power limits
One of the first questions about QRP operation is how low is low power operation. The definition of what QRP actually is varies around the globe. In areas where higher powers are common, it is hardly surprising that the limits for the maximum power for what is termed QRP operation are a little higher.
In the USA ham radio QRP operation is often considered to constitute stations operating under 100W. The UK-based G-QRP Club defines QRP as being power levels under 5W DC input. IARU Region 1 defines QRP as operation with power levels under 10W input and QRPp as operation with levels under 1W input.
Although QRPp is not an official term in many respects, it is often possible to hear the term mentioned, and it indicates a much lower level of power than normal QRP - hence the lower maximum power limit.
Along with using low power, amateur radio QRP operators usually take pride in having built much of their equipment themselves. This also brings a great sense of achievement when contacts are made. Some radio hams enjoy making their equipment by buying the components and making the equipment from scratch, while others use some of the growing number of kits that are available.
The complexity of equipment used for QRP operation varies very widely. At one end of the spectrum there are plenty of designs available for transmitters consisting of three or possibly even fewer transistors. These designs are generally crystal controlled to provide the required level of stability. However this frequency limitation is not normally a major problem because the crystal frequencies chosen can be the QRP frequencies. Often it is possible to vary the frequency sufficiently to avoid interference if a VXO circuit (variable frequency crystal oscillator) is used. These circuits are particularly popular with QRP enthusiasts who build their own equipment.
While many QRP operators may want to build equipment from components they possess in their components store, others may want to purchase a kit that they can build themselves. A good variety of kits is available and building one of these will provide a high degree of certainty that the transmitter will operate satisfactorily with a minimum number of problems.
While transmitters are often the focus of QRP equipment, many people also opt to build their own receivers as well. In order to keep the design relatively straightforward, direct conversion sets, rather then superhet receivers are very popular. These are able to offer a high level of performance without undue complexity and they are ideal for use with Morse (CW) and SSB.
In addition to this there are several sophisticated QRP transceivers that can be bought. Typically these provide both Morse (CW) and SSB and they may incorporate the latest digital signal processing (DSP) techniques.
The antenna is an important part of any station. Using low power it is essential that an efficient antenna system is used. In keeping with the spirit of QRP many people make their own wire antennas that they erect. Dipoles or various forms (single and multiband) are very popular, and there is a great amount of scope for experimentation and improvement of the performance of these antennas.
In order to allow QRP stations to make contacts without having to compete with much higher power stations, frequencies are reserved in each of the HF amateur radio bands for QRP operation. These frequencies, which are shown in the ham radio band plans, should be avoided by high-power stations to allow those using low power to have the minimum amount of interference and hence have the best chance of making their contacts. While these frequencies are reserved for QRP operation, it does not mean that QRP stations can only use these frequencies.
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QRP operation is a facet of amateur radio that has grown in popularity over the years. Despite the advance of technology providing ever increasingly more complex circuits and radios, the appeal of QRP is that it is possible to operate on the amateur bands with low powers, and generally more simple equipment that is often built by the owner of the station. In many ways it gets back to what many see as the basics of the hobby, and in this way it has a great appeal. Accordingly QRP operation will remain a major feature of ham radio for many years to come.
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