AOR SDU-5000

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AOR SDU-5000

Post by RF-Bot »

Submitted by: Jason.


OK, so I did it. I bought an AR 5000 receiver and matching SDU 5000. The AR 5000 receiver should be well known to most, but what about the SDU 5000?

What is it and what advantage does it offer to the die-hard spectrum monitor?

The common scanner or receiver plucks radio waves from the ether and by the magic of radio, turns it into sounds for your ears to enjoy. The SDU 5000 is a spectrum analyzer, a device that takes radio waves and turns them into pictures as opposed to sounds. "But what is the advantage in that?" I hear you ask. Your scanner can only tune to one frequency at a time, and your ears can only hear one or two things at a time. A spectrum analyzer can tune a huge block of frequencies in the blink of an eye, and present all of this as a picture, which your eyes can take in almost instantly. Signal frequency and strength of any visible signal of interest can be determined in a moment. A picture is worth a thousand words, as they say.

The advantages of this should be obvious by now; any frequency that pops up will be instantly noticed, its frequency noted, and tuned a few seconds later. If you are looking for that elusive signal, keeping an eye on the spectrum with this device will enable you to nail that frequency much quicker than by conventional means. This process is much quicker than waiting for the somewhat hit-and-miss affair of searching frequencies and waiting for the scanner to find an active frequency. With some manipulation, precise frequency, bandwidth and even modulation can be determined once you zero in on a frequency of interest, and all this before you reach for the controls on your scanner.

So, is the SDU 5000 a 'real' spectrum analyzer? I have access to a Hewlett Packard 8594E spectrum analyzer with all the trimmings: 0.1 Hz resolution, tracking signal generator and high stability oscillator options. Real lovely piece of equipment, too. Of course, there's no way that this $70k piece of test equipment could be compared to a sub $2k item, but it makes for a convenient reference to make a comparison. The real spec-an is a stand alone piece of equipment, just plug it in to the power, add an antenna or other source of radio signals, and stand back and watch. The SDU 5000 is a little different in that it is not a stand alone device; it requires a receiver to work with. The SDU 5000 uses your receivers front end and IF (Intermediate Frequency) stage to tune the radio spectrum, and the SDU 5000 does the rest. You will need a receiver that is capable of a 10.7 MHz IF output. Many receivers use this IF as standard, and most of these could be modified to have a suitable buffered IF output. My own AR 5000 already has this feature conveniently built in. Note that the accuracy of the results obtained by the SDU is reliant on the 'host' receiver. Have a poor frequency reference or sloppy or lopsided IF in your receiver and your results will suffer.

The second difference is that of specifications. The HP spec-an can sweep from 9 KHz to 2.9 GHz all at once, where as the SDU can only 'see' a 10 MHz chunk at once and the frequency range is limited by the radio it is connected to. Have a scanner that receives from 25 to 1300 MHz, then you'll have a spectrum analyzer with the same coverage. The HP has a resolution bandwidth of 0.1 Hz, the SDU can only manage 5 KHz. Sweep time is variable on the HP, but not the SDU. In short, the Hewlett Packard wonder machine allows its operator control over all conceivable parameters, whereas the SDU has many parameters fixed.

With the SDU, you are in command of the sweep width from 10 MHz down to a lower practical limit of 25 KHz, the RF gain and attenuation of the device, the resolution bandwidth (5 or 30 KHz) and a marker is provided so that you can place a cursor on a signal of interest and see its frequency and amplitude. There is also a peak-search, peak-hold and average signal strength feature. So, as you can see, it has fairly limited features when compared to the Hewlett Packard, but all the basics are there, and for a lot less of the folding stuff.

Having laid bare all the shortcomings of the SDU, it should be noted that the SDU did exactly what it was supposed to, and did it very well. Letting it loose on all manner of signals across the spectrum was certainly an educational experience. Shortwave signals are a little difficult to obtain any sort of sensible results from due to the fading and phase disturbances that affect such frequencies, but where signals are a little more stable, such as at VHF and above, the results really shine. It is fascinating to compare bandwidths, signal strengths and centre frequencies of various signals, especially of CB signals. It is amazing just how scruffy some of the RF is from these sources (not to mention their aural content!) Looking at some microwave links at around 1.5 GHz revealed the nature of these wideband signals with the ease that a simple receiver could not possibly hope to achieve. Incidentally, signal strength is measured in dBm, rather than the S scale.

The SDU 5000 has a small 60mm square 16 colour LCD screen which does need to be at a good viewing angle, otherwise it fades. At 190mm x 92mm x 250mm (WHD) it's not a huge table-space hog. The front panel buttons are the touch sensitive membrane type, similar to the very first Touch Phone 200s. The case is made of metal, and so makes it quite sturdy. The rear panel sports a IF input BNC connector, a PC control input, and another computer connector that connects to the host radio. More on this in a minute. There is a video output, so you can connect the SDU to a TV for a larger display, and a selector switch for the TV format (PAL or NTSC). There is also a 12 VDC power inlet, which brings me to an interesting point. The SDU does not come with a power supply. You'll need a 12 - 14 volt DC regulated power supply, capable of supplying 1 amp.

The instruction manual is adequate, with a few amusing pieces of 'Jinglish' (English that results from the translation from Japanese) such as: "Internal LCD display is made of grass" and "The brightness of the LCD display is adjustable by the volume on the side". He he he. Don't forget to water and fertilize the 'grass' LCD display once a week, will you?

The SDU is capable of operating with just about any radio that has a 10.7 MHz IF output as mentioned before, however its operation is enhanced with a computer control connection to the host radio, so that the front panel controls of the SDU can also set the mode, step, frequency, and attenuation of the host radio and at the touch of a button tune the scanner to any detected signal of interest or step up or down in whole 'pages' equal to the current sweep width of the SDU. Models that can be controlled by the SDU are: AOR 3000A and 5000, Icom 7000, 7100 and 9000. In addition to this, you can have a real computer controlling both the SDU and host radio, via the second computer control port.

So, to the original question: is the SDU 5000 a serious tool or a toy? Given that the SDU 5000 does not have a sweep width of obscene proportions and a fine resolution bandwidth, you are forced to say no, it is not a serious tool, but then it does have professional features, and is quite a powerful tool in its own right. It would be fine for 'quick and dirty' measurements, but don't go relying on it to do anything too serious. Given that it can perform spectrum analysis functions at a much lower price than a 'real' spectrum analyzer, it represents serious 'bang for your buck'. The SDU can be yours for around $2000. Think of it as getting a 90% spec-an at 10% of the price.

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