VK3YE amateur radio pages

QRP Equipment

 

All material on this site (c) Peter Parker VK3YE
1997-2013.

Material may not be reproduced without permission.

 

 

Picture of QRP equipment

There is a wide range of equipment available for the QRPer. This ranges from commercial rigs that can be wound back to QRP power levels, commercially-available QRP transceivers, build-it-yourself kits and homebrew transmitters and transceivers. This section outlines the main choices available and provides information to assist the operator in making an informed choice.

QRO equipment wound back to QRP

Today's 100-watt transceivers can often be wound back to deliver QRP power levels.  Their coverage of the WARC bands (10, 18 & 24 MHz) and DSP make them attractive to the operator who wishes to try QRP but also retain QRO capabilities.

Many of the SSB/CW rigs of the late 1970s/early 1980s came in low power versions (10w typical) to suit Novice licensees. Examples included the Yaesu FT-7, Yaesu FT-77S, Kenwood TS-120V and the Shimizu Denshi SS-105S. These rigs are still good performers, but lack extras such as WARC bands, 160 metres and digital signal processing found on newer transceivers.

Modern 100-watt equipment boasts an impressive array of interference-beating features, such as noise blankers, notch filters, variable tuning rates, IF shift and digital signal processing. For this reason, this gear provides excellent results when trying to receive marginal signals from distant QRP stations.

Though equipment is getting smaller, commercial rigs are usually still heavier than single-band homebrew or kit rigs. The main shortcoming of QRO equipment for portable use is power consumption - this often exceeds 1 amp on receive. 1 amp is more than most dedicated QRP rigs use on transmit! Receive power consumption is especially important for QRPers as most time is spent listening rather than transmitting.

Commercially-available QRP equipment

When QRP first took off in the late 1960s, spurred by the increasing availability of solid state RF devices and the rediscovery of direct conversion receivers, a number of American manufacturers produced equipment specifically for QRPers. Probably the most famous is the Ten-Tec Argonaut series (505, 509 and 515) of the 1970s. The Argonauts, though lacking today's refinements, provided good performance and are still sought after despite their large (and not particularly rugged) enclosure, crude tuning dial and odd choice of power and antenna connectors. $200 to $250 is a fair price on the used market for a working Argonaut 509. Ten-Tec has since produced other QRP transceivers, but these are uncommon in Australia. Other manufacturers that have been active in the QRP equipment field include MFJ, Mizuho and the ironically-named Tokyo Hy-Power.

Later on was the Index Labs QRP Plus and SGC-2020 transceivers, offering CW/SSB operation over a wide band range. These rigs have received mixed reviews, especially from QRPers who enjoy CW.

  By far the most popular QRP rig of recent times is the Yaesu FT-817 (pictured above). Unlike previous QRP rigs, the '817 operates on all bands between 1.8 and 450 MHz and has a compartment for optional internal batteries. It provides 'big rig' performance in a tiny package and has provoked renewed interest in back-pack and pedestrian mobile operation. The FT-817 came out in 2001 and is still available more than 10 years later as the slightly updated FT-817ND.

Lately a lot of attractively priced QRP equipment has started coming out of China from supplier such as YouKits. Quality, reliability and finish varies and you would be well advised to read reviews before purchasing.

QRP kits

QRP constructors have a variety of kits from which to choose. These range from no-frills crystal-controlled transmitters to multiband CW/SSB transceivers.  QRP kits can be club projects for members or be available on the commercial market. Some are even designed and produced in Australia. The results obtained from a good kit on the right band make this choice worthwhile, especially for the time-poor constructor.

The Elecraft K2 is widely regarded as the best QRP rig ever produced. This is an all band HF SSB/CW kit for the experienced builder. Its smaller brother is the K1 - a simpler CW-only transceiver kit for the sensible 40/20 metre band combination. The KX1 is even smaller, expressly designed for field portable work. If you want SSB in a small package, consider the KX3. Though if you're anything like me you'll be nervous about taking such high-grade equipment to some of the harsher portable locations.

SSB kits are normally either discrete component based (eg the BitX) or NE602 based (eg the MST series from OzQRP). Both designs perform well and are easy to build. The BitX is open source and several suppliers offer boards and/or full kits. There are many demonstrations on YouTube of various versions. I would recommend building a few simple projects first before moving on to a single band SSB transceiver kit. Multiband kits are recommended for the advanced constructor only unless the modules are pre-built, as with some Elecraft products.

There are some overseas kits that the Australian builder should avoid. These include most crystal-controlled transmitters, especially when the kit includes a crystal on a frequency far removed from VK activity. The same is also true for some of the simpler VXO kits that only give a few kilohertz shift – rarely sufficient for Australian working conditions. Also steer clear from some of the ultra-simple kits that only put out a few hundred milliwatts or have ultra-simple receivers with poor audio filtering, etc. Such rigs are much better built from scratch for only a few dollars from junkbox items.  If you're going to buy a kit, pay that little bit extra and get one that will be a pleasure to operate for years to come.

Because most kits only operate on a single band, you will need to select a band before you order. Don't rely on reports from overseas – activity here is less, and a rig that will make contacts in more populated countries may only produce many unanswered CQs in VK/ZL. Select a popular band that will be open throughout the solar cycle and produce contacts at the times you plan operating.  Reach a decision based on your own operating and listening assisted by information elsewhere on this webpage. My own preference would be 40 and 20 metres first, followed by 80, 15, 17 and 30m.

Already-built QRP kits occasionally appear on the second-hand market, either at hamfests or eBay. The old Heathkit HW7/8/9 series almost qualify as vintage these days. Of these kits, the HW-8 was the most popular. It is stable and has a good receiver, and is much to be preferred than the earlier HW-7. 

Other QRP rigs to look out for include anything by Elecraft, Hendricks, Oak Hills Research and OzQRP. Information on these is widely available on the web.

You'll aldo find reviews of prebuilt and kit QRP rigs on eHam, while some have their own email list.

Homebrew QRP equipment

QRPers also have the option of building their own rigs. And a surprising number do. Homebrewing is the way to go if you want a rig that is personalised to your interests and preferences. For example, you may require a particular band combination and an unusual ability to switch audio bandpass and notch filters for best reception. A homebrew rig may also be a platform for development of a high performance receiver, or novel transmitter arrangement, for example.

Some general components for homebrew transmitters and transceivers can be obtained from the usual parts suppliers, while the more specialised parts (toroids, variable capacitors, NE602s, etc) can be found at amateur hamfests, junk sales, eBay or purchased by mail from the VK QRP Club.

Transmitter or Transceiver?

A key decision for the constructor is whether to construct a transmitter or transceiver. A transceiver is easier to operate and less bulky – major advantages for portable operating. However a transceiver is more complex, especially where many stages are common to both the transmitter and the receiver.

A transmitter is recommended over a transceiver for the beginner as it uses fewer parts and is easier to troubleshoot.  In many QRP transceivers, the receiver may account for two-thirds of all components used. Leaving out the receiver makes for a simpler and quicker project that is more likely to work first time.   Also, the use of an outboard receiver means that the transmitter/receive frequency offset circuit can be dispensed with, further simplifying circuitry. Another point in favour of the separate transmitter/receiver approach is that most QRPers will already have a suitable communications receiver available. The performance and ease of use obtained will typically be better than that from a simple homebrew receiver.

A good plan is to build the transmitter in an oversize box. Once the transmitter has been got working, it can be expanded.  For instance, a direct conversion receiver can be added. Or an extra band. Or, maybe even the parts required to generate a DSB or SSB signal.

Choosing a design

What type of transmitter circuit should you start with? Sure, it's very easy to build a simple 80 metre QRP Morse Code rig. Just one or two transistors and a 3.58 MHz TV colourburst crystal, and you're on the air. But will the rig sound OK? Will you get contacts? Or will the rig cause you to give up QRP because no one is responding to your CQs?

This website is devoted to practical QRP. QRP that works. QRP that's fun. And to get the most enjoyment from QRP, you need to know something about the capability of your equipment so that you don't expect too much and become disappointed when your hopes do not materialise.

That's why you have to be selective about the type of QRP rigs you build. Firstly it must be fairly simple and not require too many hard to get parts. Secondly, it must be put out enough power to be heard on the air. Thirdly, it should be frequency agile over at least a segment of the band. The following sections explore these points in depth.  The author's minimum standards for homebrew rigs should also assist the builder to cull the good from the useless from the hundreds of circuits available.

Power

What is sufficient power? Though this depends on the distances you wish to work, I would say that an inexperienced amateur aiming to make regular contacts with powers of less than one or two watts on any HF band is going to be disappointed. Sure those milliwatt rigs you see described in foreign magazines and on the web do work, but remember that Europe and the USA have far more amateurs per square kilometre than we have in Australia. As it's so easy to build one or two watt transmitters that there is little sense in settling for less unless you specifically want to do experiments in milliwatt communications. 

I would recommend powers of 1-2 watts as a practical minimum assuming you are using a reasonably efficient antenna (eg a full-sized dipole). Though there will be times when more power than this will be required (eg when static is bad), you should be rewarded by reasonably frequent contacts up to several hundred kilometres, and the occasional two or three thousand kilometre contact with 1-2 watts. On 40 metres 1 – 2 watts is again sufficient for distances of up to about 1000km, and the proportion of Q5 signal reports tends to be higher than on 80. 

On 20m and up, Europeans and Americans can regularly be worked at the 2-watt power level, especially if portable overlooking water. Don't expect reliable DX contacts from home with this level with low dipole or vertical antennas, however. 

PSK-31 is a highly effective mode, and long-haul DX almost every day is quite possible with 5 watts and an indoor antenna.

SSB requires more power for comparable results, but even so 5 or 10 watts can be rewarding, even in the middle of the 20 metre 'kilowatt alley'. Very low output powers can be very successful on the higher bands, but you need to be there at the right time – the kilowatters may enjoy DX for hours, but the QRPer must be there when the band is optimum. 

Frequency agility

Then there's frequency agility - being able to move around the band, rather than being stuck on a single frequency. Most home brew QRP transmitters are crystal-controlled. Most of them also sit on the shelf gathering dust and are seldom used. Why? Being locked on one frequency severely hampers your operating success. You could be calling CQ, but not be getting any replies. Then 5 kHz up the band, you hear another station also calling CQ. If you were frequency agile, you could move to the other station's frequency and most likely obtain a contact. Instead, you remain on your frequency, hoping that the other station will not get a reply, stop calling, tune around and eventually find you. A lot of people build simple rigs, have one or two contacts, and not use them again because getting contacts is sheer hard work.

The disadvantages of crystal control are greatest with QRP. Unless someone happens to start calling on 'your' frequency, the only way to get contacts is to call CQ yourself. As many people tend to reply to CQs from stronger stations only, your chances of getting a reply are reduced if your signal is weaker. The successful way to get contacts with QRP is to 'search and pounce'. Either reply to CQ calls from other stations (you know at least someone is listening for your call), or 'tail-end' contacts that are concluding. Both of these techniques are only really possible if you can move frequency. And, if there is not much activity around, and you do wish to call CQ, chances are better if the call can be made on a perfectly clear frequency. The probability of finding such a frequency is of course much greater if you can operate everywhere in the band.

Another limitation of crystal control is that your crystal may not be in the most active part of the band. For example, 3.58 MHz TV colourburst crystals are conveniently in the middle of the 80 metre Novice allocation. However, most CW activity is below 3.550 MHz. Operators seeking CW contacts will not often be tuning across 3.58 MHz. So, the chances of getting a response are reduced as you are not where most potential contacts will be listening.

Even crystal-control on the so-called International QRP Frequencies (eg 7.030 & 14.060 MHz) can be very limiting, at least in VK/ZL. These frequencies are sometimes clogged by strong digital mode QRM, and are made useless as a result. This disadvantages the constructor who has built a rockbound 'OXO' or 'Cubic Incher' rig that is stuck on the single frequency. Though authors describing such projects invariably report great success with their one or two transistor creation, bear in mind that they in Europe or North America, where the amateur population is at least 20 times Australia's.   Attempts by Australian amateurs to operate such transmitters often lead to fruitless CQs, followed by grave disappointment with the lack of contacts achieved.

To summarise, because 'search and pounce' (answering calls and tail-ending) is the best way to get contacts, frequency agility is essential for the QRPer. Use nothing less than a VFO, good VXO, or stable variable frequency ceramic resonator oscillator to succeed with QRP.

Mode

If you are building a voice rig, should you choose AM, double sideband suppressed carrier (DSB) or SSB? An SSB rig is a challenging project, and is not recommended unless you've already built CW and DSB transmitters. So, for the newcomer (and even for many experienced amateurs), the choice is between AM and DSB.

AM was used prior to the advent of SSB, and still has a following on some bands (especially 160 metres, to a lesser extent on 80 and 40). However, many SSB rigs do not have AM and it may not always be easy to resolve a weak AM signal on an SSB transceiver. Because AM signals include a carrier that does not contribute to the intelligibility of the signal, AM is less efficient than SSB, and more transmitting power is required to make oneself heard. However, AM still has its uses. The speech quality of AM is generally better than DSB or SSB. Where you have a small group interested in local contacts only (such as within a country town or small city), a homebrew AM rig would be a fun project, particularly on 160 or 10 metres where there is plenty of band space. Ranges of up to about 5km can be achieved with powers of under a watt.

DSB has an equivalent bandwidth to AM, but has no carrier. Thus it is a more efficient mode. As well, DSB is fully compatible with modern SSB equipment, and unless you tell them, many SSB stations will not know that you are using DSB. The combination of a direct conversion receiver and DSB transmitter is highly recommended for the Novice wanting to build an HF voice station, and because of the similarity of DSB and SSB. Also, DSB transmitters can later be upgraded to SSB by adding extra circuitry. DSB is particularly recommended for bands such as 160, 80, 40 and 10 metres due to the ample space on these bands.

For the experienced homebrew constructor, SSB is undoubtedly the most rewarding voice mode as it's the hardest to build a transmitter for. The builder is entitled to take personally the reports of outstanding audio that accrue as the transmitter is all his own work. Also transmitting your voice (and not just dots and dashes) over 20 000 kilometres with a transmitter you built yourself is a thrill hard to describe.

Minimum standards for homebrew rigs

Taking into account the above observations based on years of practical experience, I am now in a position to lay down some minimum standards for practical homebrew rigs. These are:-

1. Power output at least 1-2 watts

2. At least some frequency agility in a popular part of the band

3. CW and/or DSB/SSB operation.

If you see any design or kit that does not meet the above, have second thought about building it, even if it appears cheap and simple. Even if it works according to the book, you will soon become disappointed with is limitations.

Meeting the minimum standards for homebrew rigs

1. Power output

Look for a design with a reasonable power output transistor. A BFY51, 2N3053, 2N3866 or 2N4427 in the transmit final stage should have an output close to 1 watt. 2N3553, BD139, IRF510 or IRF511s are all capable of power outputs between 2 and 4 watts. Two lower power transistors can be wired in parallel (with suitable emitter resistors) to produce more output. A 2N2222 or BC548 as the final amplifier is a sure sign that the rig is nowhere near powerful enough.

2. Frequency agility

A free-running VFO or synthesised VFO usually provides full band coverage, but can be difficult for the newcomer to get going properly. It is not always easy to obtain good frequency stability in a free-running VFO on the higher HF bands, and synthesisers tend to be somewhat complex to build. Nevertheless, a free-running VFO is a good choice for an 80 metre rig provided that care is exercised in its construction. Cheap 3.58 MHz ceramic resonators are also good for use on 80 metres - stability is acceptable, and the pulling range can be as much as 100 kHz, neatly covering the Australian 80m Novice portion. Ceramic resonators are excellent for 80m CW or DSB direct conversion receiver and transmitter projects. Quartz crystals are not recommended on 80 metres as they cannot be shifted very far in frequency. However, at 7 MHz and above, crystal oscillators (VXOs) can be pulled to provide worthwhile coverage of frequencies immediately below the crystal's nominal frequency. Ranges of 5 to 30 kilohertz can be achieved, depending on the crystal type and the operating frequency. VXOs particularly useful for CW/DSB equipment on 40, 30, 20, 17 and 15 metres. Frequency multipliers are required on 12 and 10 metres because of the inability to shift crystals in overtone oscillator circuits.

3. Mode

DSB/SSB  transmitters require a balanced modulator stage to null out the carrier signal. Devices such as the NE602 (also used in direct conversion receivers) can be used. Many older published designs use other ICs (CA3028 and MC1496) or two or four diode balanced mixers). Like in an SSB rig, power amplifiers used in DSB rigs have to be linear. This means that a power amplifier circuit used in a CW transmitter is normally unsuitable for DSB unless its operation is made linear.