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WiNRADiO ® By Maurie Findlay, MIEAust Excalibur A revolutionary radio receiver In the legend of King Arthur, “Excalibur” was a sword with magical properties. It is an appropriate name for the latest Software-Defined High Frequency Receiver from WiNRADiO of Melbourne, Australia. Like its namesake, Excalibur is immensely powerful and – dare we say it – almost magical in performance! S ixty years ago, communication receivers used vacuum tubes and came with precision mechanical dials in big metal boxes. Thirty years ago, transistors and integrated circuits had replaced the valves and the boxes were smaller. Today, this new receiver does a great deal more than any of the former and comes in a very small sealed metal container – just 156 x 97 x 41mm. A purchaser receives a professionally presented package which includes 20  Silicon Chip the receiver, power supply, cables, user’s guide, an SMA/BNC adapter for the antenna socket and a CD-ROM with the application software. It is assumed that a computer, essential to the operation of the receiver, is already on hand. The user’s guide discusses the requirements for the computer. The one I used is a four year old laptop, Compaq Presario V6000 running Windows XP, and is about the minimum standard suitable for the job. Windows 7 or Vista would be the operating system in more modern computers. The hard disk must have at least 20MB of free space to hold the information from the CD-ROM. After connecting the receiver, loading the CD-ROM and attaching a random (short) length of wire to the antenna socket, I followed the user’s guide and within five minutes was hearing my local station on 702kHz, through the speakers in the computer. Another five minutes and I was able, siliconchip.com.au one by one, to tune in all my local stations on the default AM setting of the receiver. Yet another five minutes with the guide and I was able to receive the local stations in the USB (upper sideband) and LSB (lower sideband) modes. That is, with the receivergenerated carrier substituted for the incoming carrier. It is that easy to get started. The 107-page User’s Guide is packed with well written information. Most owners, new to software-defined high frequency receivers, will take several weeks to fully appreciate the facilities offered by Excalibur. In addition to the manual, there a great deal of helpful information on www.winradio.com DDC? DDS? SDR? Although I have a background in the design and manufacture of commercial siliconchip.com.au radio equipment ranging from the valve days to high performance types using semiconductors, I am one of those new to this technology. For the first time, in the guide, I came across abbreviations such as DDC, DDS and SDR. For the uninitiated (like me!) these stand for digital down-conversion, digital direct sampling and software-defined receiver. While these are explained early in the guide, it would have been easier to study if these abbreviations had been spelled out at the beginning of each section where they occur. A detailed index at the rear would have made the job of finding information easier. There is a 3-page table of contents at the front. The initial screen is shown above. It is pin sharp and full of detail. The panel at the top left indicates the frequency to which the receiver is tuned, in this case 1278kHz; towards the high frequency end of the standard medium wave band. To the right of the frequency indication is a knob which can be operated by the computer (mouse) to change the End-on view of the WiNRADiO Excalibur WR-G31DDC HF receiver, shown here close to life-size. Controls on the box are non-existent; everything is done by the attached computer. June 2012  21 ated by the press-to-talk switch, is not satisfactory because the proximity of the active arm of the relay and the receiver contact will allow appreciable power to be transferred. A specialised antenna changeover circuit, designed for the task, should be used. Audio quality, particularly the lower end of the range, is limited by the small speakers built into the computer. For many users this will be all that is required. However all computers these days have an audio output jack which can be used to feed a better quality audio system. Modes G31DDC receiving a broadcast station on 1278kHz with the spectrum displayed in the “Waterfall” mode. It makes a colourful change! frequency. Alternatively, the frequency can be entered from the keyboard. The receiver covers the range from 9kHz to just below 50MHz. To the right of the knob is a meter indicating the strength of the incoming carrier: in this case -28dBm. The buttons below the meter allow the strength to be indicated in dBm, µV or “S” units, the last being the usual means of reporting signal strength on the amateur bands. Buttons at the top right, accessed by the mouse, allow the receiver to be set for nine different modes of reception: AM, AMS, LSB, USB, CW, FMN, FSK, UDM (user-defined mode) and DRM mode (optional). Below them are a further eight buttons which access other functions including volume, squelch and noise blanker. Spectrum analyser Across the bottom of the screen is a spectrum analyser display, in this case set to cover 0 to 30MHz. Strong signals in the AM broadcast band appear to the left. Above that is the spectrum, expanded to cover the band from 0.5 to 2MHz. Individual carriers of the local stations can be picked out very clearly. A third display, to the centre right, covers only 50kHz and allows the audio spectrum of the incoming signal to be seen. The shaded area indicates the receiver bandwidth and can be changed by clicking the “BW presets” button above that display. So in addition to being a high performance communication receiver, 22  Silicon Chip Excalibur is a very useful spectrum analyser. It is designed to match an antenna with a source impedance of 50Ω and the short length of wire I used initially is not very efficient. The receiver can be used for general shortwave listening with a long length of wire, attached to the antenna terminal and preferably outside the building but even this does not give the best results. WiNRADiO are able to supply an aerial transformer which gives better results with random lengths of wire. The transformer is connected to the receiver via coaxial cable and can be placed well away from any local sources of interference. A ground point can be connected to the transformer. Commercial users and amateur radio people using the receiver will normally have tuned 50Ω antennas which can be directly connected to the antenna terminal. In this case, of course, it will only work efficiently for the particular band and the spectrum analyser will clearly indicate the resonance of the antenna. Because of the spectrum analyser presentation and many other features, amateur (and perhaps even professional) radio operators may use the WiNRADiO Excalibur to replace the receiver section of an older transceiver. Great care must be taken with the switching arrangement to ensure that radio frequency energy from the transmitter does not reach the receiver antenna terminal. A simple changeover relay, oper- Modes of reception for the receiver include the conventional AM (amplitude modulation), LSB (lower sideband), USB (upper sideband, not to be confused with the universal serial bus USB) and CW (continuous wave - for Morse code). In addition, AM can be received as AMS (amplitude modulation - synchronous demodulation) in which case the received carrier is replaced by a locally generated carrier. One or both sidebands can be selected. This results in a reduction of the distortion caused by selective fading, particularly with weak signals on the shortwave broadcast bands. Narrow band FM (frequency modulation) signals can also be received. Digital, frequency shift keying and user-definable modes are also discussed in the User’s Guide. Selectivity is variable in fine increments from a bandwidth of 50kHz to 10Hz. The former is suitable for wideband AM and the latter for CW under difficult conditions. The standard mode for voice communications on the high frequency bands is SSB and a bandwidth of around 3kHz can be selected for best signal-to-noise ratio. Upper sideband is normal, although radio amateurs use lower sideband on frequencies below 9MHz. There is no special technical advantage in using LSB; it goes back to the early history of the development of sideband on the amateur bands. Tuning accuracy is given as 0.5 parts/million <at> 25°C but the sample provided for review was better than that. Furthermore, the User’s Guide shows a method of adjusting the internal crystal oscillator against an external standard. This is of immense value when using the WiNRADiO Excalibur siliconchip.com.au WiNRADiO WR-G31DDC ‘EXCALIBUR’ SPECIFICATIONS Receiver type:.....................................................................................Direct-sampling, digitally down-converting software-defined receiver Frequency range:................................................................................9kHz to 49.995MHz Tuning resolution: ..............................................................................1Hz Modes:................................................................................................AM, AMS, LSB, USB, CW, FMN, FSK, UDM (user-defined mode) DRM mode (optional) Image rejection:..................................................................................90dB typical IP3 (intercept point 3rd order):...........................................................+31dBm typical Attenuator:..........................................................................................0 - 21dB, adjustable in 3dB steps SFDR (spurious free dynamic range):.................................................107dB typical Noise figure: .......................................................................................14dB MDS (minimum discernible signal): ...................................................-130dBm <at> 10MHz, 500Hz BW Phase noise: .......................................................................................-145dBc/Hz <at> 10kHz RSSI (received signal strength indication) accuracy:..........................2dB typical RSSI sensitivity: .................................................................................-140dBm Processing and recording bandwidth (DDC bandwidth):....................20kHz - 2MHz (selectable in 21 steps) Demodulation bandwidth (selectivity): ...............................................10Hz - 62.5kHz (continuously variable in 1Hz steps) Spectrum analysers:...........................................................................Input spectrum/waterfall, 30MHz or 50MHz wide, 1.5kHz resolution bandwidth ...........................................................................................................DDC spectrum/waterfall, max 2MHz wide, 1Hz resolution bandwidth ...........................................................................................................Channel spectrum, max 62.5kHz wide, 1Hz resolution bandwidth ...........................................................................................................Demodulated audio, 16kHz wide, 1Hz resolution bandwidth ADC (analog/digital converter):...........................................................16 bit, 100 MSPS (mega-samples per second) Sensitivity (typical <at> 10MHz):............................................................AM -101dBm (2.00 µV) <at> 10dB S+N/N, 30% modulation ...........................................................................................................SSB -116dBm (0.35 µV) <at> 10dB S+N/N, 2.1kHz BW ...........................................................................................................CW -123dBm (0.16 µV) <at> 10dB S+N/N, 500Hz BW ...........................................................................................................FM -112dBm (0.56 µV) <at> 12dB SINAD, 3kHz deviation, 12kHz BW, ...........................................................................................................audio filter 300-3000Hz, de-emphasis -6dB/octave Note: Below 200kHz, the sensitivity gradually drops. Typical figures (CW, 500Hz BW, 10dB S+N/N) are as follows: .......200kHz -123dBm; 100kHz -116dBm; 50kHz -112dBm; 25kHz -97dBm; 10kHz -81dBm Tuning accuracy:.................................................................................0.5 ppm <at> 25 °C Tuning stability: ..................................................................................2.5 ppm (0 to 50 °C) MW filter: ...........................................................................................Cut-off frequency 1.8MHz <at> -3dB; Attenuation -60dB min <at> 0.5MHz Antenna input: ....................................................................................50Ω (SMA connector; SMA to BNC converter supplied) Output:................................................................................................24-bit digitised I&Q signal over USB interface Interface: ............................................................................................USB 2.0 Hi-speed Dimensions:........................................................................................156 x 97 x 41mm Weight: ..............................................................................................430g Power supply (operating): ..................................................................11-13V DC <at> 500mA (typical, operating); 45mA (typical, power save) Operating temperature:.......................................................................0 to 50 °C as a communication receiver because the boys”. First is sensitivity – the abilthe transmissions are frequently too ity to receive very weak signals; the short to give time for retuning. With other is blocking performance – the this accuracy, you can be sure of clear ability to receive those weak signals in audio even with SSB at the higher the presence of strong signals on adjafrequencies. cent frequencies. This is particularly A feature of the receiver is the abil- important on the crowded amateur ity to receive three signals at the one bands. time provided that they fall within the There are a number of accepted tests range of the DDC (digital down con- for sensitivity and blocking. I decided verter) analyser which has a maximum to apply a simple test, that I have used bandwidth of 2MHz. previously in my own laboratory, to This could be of value on the ama- the Excalibur receiver. teur bands; however most of the allocated channels 25 25 for the marine, flying doctor and VKS-737 high frequency SIGNAL RECEIVER GENERATOR UNDER TEST networks, that you may wish 1 to monitor at the same time, are separated by more than 25 25 2MHz. Sensitivity & blocking There are two features of communication receivers which separate “the men from 24  Silicon Chip It was tuned to 10,000.0kHz SSB (upper sideband), with a bandwidth of 3kHz, and a signal at 10.001.5kHz applied to the antenna terminal. The signal generator has a source impedance of 50Ω and the receiver a nominal input impedance of 50Ω. The attenuator of the generator indicates the signal level at the receiver. (The audio output of the receiver is a tone at 1,500Hz.) The output of the signal generator was reduced until the signal plus noise to noise ratio of the output was 10dB. The signal level at the antenna terminal was -112dBm (0.5 µV). Now for the hard one. A resistive network was arranged so that two signal generators could be connected to the receiver, both generators being correctly SIGNAL AUDIO terminated and the source reGENERATOR LEVEL METER 50 2 sistance, as seen by the receiver, still 50Ω. The level of the first generator was increased so that The test setup I use for communications receivers. It revealed an outstanding result. the S+N/N was still 10dB. siliconchip.com.au The second signal generator, tuned to 10,020Hz, was fed into the network and the level adjusted until the S+N/N changed by 3dB. The level at the receiver terminal when this happened was -7dBm (0.1V). That is, 105dB above the wanted signal. All these tests were done without the input attenuator of the Excalibur in operation. A figure of 90dB was considered the norm for high-standard communication receivers when I was involved in their design and manufacture – so at 105dB this receiver is very good indeed; exceptional, in fact. However, it could be even better: discussions with WiNRADiO engineers suggest that shortcomings of the signal generators I used may have influenced the test so that the real blocking figure may well be greater than 105dB. Interference? Notch it out! The Excalibur has another trick up its sleeve, for dealing with high level adjacent channel blocking signals, in the form of a notch filter. This can be brought into operating by clicking the Notch button when the frequency and width of the notch can be adjusted. (The interfering signal can be seen on the analyser display.) Space in the User’s Guide is devoted to the elimination of interference, particularly that from the computer, which is an essential part of the receiving setup. When I initially operated the receiver, with a short length of wire close to the computer for an antenna, the interference was obvious. However, when an outside length of wire or a tuned antenna was used, computer noise was swamped by the incoming signals (as you would expect). Obviously, the noise generated by various computers will be different but with my “typical” PC, performance was outstanding. It is not true to suggest that newer PCs may be better in the noise department than older models – some recent PCs (escpecially plastic-cased laptops and notebooks) have been woeful in this regard compared to their forebears. But I am confident in suggesting that with rare exceptions (and a proper antenna) computer noise should not be an issue. Software control of the receiver makes possible a large number of useful adjustments and displays which would be quite impractical with the conventional design. One of the most important is the ability to vary the bandwidth in small increments. A conventional superhet may have a crystal filter with a bandwidth of 6kHz for AM and another with 3kHz bandwidth for single sideband but there will be times when different selectivity will allow better reception. The Excalibur has a conventional spectrum analyser, which plots frequency against amplitude (ie, frequency domain), while frequency may be plotted on a linear scale in the horizontal and amplitude on a vertical logarithmic scale. It also offers the alternative of a “waterfall” display, which some users may prefer. Other facilities offered by the Excalibur include the ability to record various settings and also received programs. Would you like to work for this innovative company? WiNRADiO ® is seeking bright, enthusiastic Electronics and RF Technicians/Engineers for R&D work, prototyping, testing and production. Interested? Then send us your application with your professional background addressed to: careers<at>winradio.com WiNRADiO Communications 15 Stamford Road Oakleigh, Vic 3166 Ph (03) 9568 2568, ext 0204 Conclusion The WiNRADiO G31DDC Excalibur offers a tremendously powerful performance at a cost less than that of a conventional communicationsstandard superhet receiver. This is the way of the future. It is sold direct from WiNRADiO’s online store in Australia or through a number of specialist communications distributors overseas. For readers who don’t have Windows-based PCs, WiNRADiO also have available MacRadio and LinRadio (Linux) versions. Acknowledgement: We gratefully appreciate the assistance of Helmut Riexinger of WiNRADiO Communications in the preparation of this review. SC Where from, how much: The WiNRADiO Excalibur WR-G31DDC receiver is made in Australia by WiNRADiO Communications, 15 Stamford Road, Oakleigh, Vic, 3175. Phone: (03) 9568 2568 Web: www.winradio.com Recommended retail price is $995.00 +GST The spectrum analyser displaying the demodulated signal from a broadcast station. The shaded area indicates the sidebands, each side of the carrier (the peak in the centre), which are passed on to the audio amplifier. siliconchip.com.au Readers in Australia should contact WiNRADiO direct via their website or phone; readers in other countries can contact their local distributors (details on the WiNRADiO website) June 2012  25