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Part 1 THE AOR AR7030: A BOLD NEW RECEIVER FROM BRITAIN Guy Atkins
Every now and then a new receiver design comes along which breaks the mold of conventionality and causes a flurry of discussion among radio hobbyists. Such was the case with the Drake R-7/R-7A of the late 1970s, the ICOM R-70 in the early 1980s, and the Watkins-Johnson HF-1000 at the beginning of this decade. A case could be made for other receivers, but these three caused a stir in the areas of performance, features, and price point.
Now in 1996 the British have come up with their own notable--and controversial--communications receiver. How well does it perform for the mediumwave and tropical bands DXer? This article will present an overview of performance and features, and a "hands-on" report.
BEHIND THE SCENES
Talented designer John Thorpe is the individual responsible for the AOR AR7030. He became known to hobbyists as the man behind the "HF" series of receivers for the UK's Lowe Electronics, including the highly-regarded HF-225 Europa. Many had expected Lowe Electronics to continue the progression, but the HF-350 was never produced (remember the mysterious "Project N"?). Thorpe and Lowe Electronics parted ways in a not-so-amiable fashion, with Lowe going on to produce the traditional--and "comfortable"--HF-250. Thorpe took the road less traveled by joining forces as an independent designer with the AOR Corp. and creating the unconventional AR7030. This receiver is manufactured at AOR's new UK facility in Belper, Derbyshire.
Well-balanced performance, sturdy construction, and minimalist controls are qualities that have marked John Thorpe's previous receiver designs. These characteristics are present in the AR7030 as well but there are unusual features sprinkled liberally throughout. Among these are auto-tuning synchronous detection, onboard filter calibration and measurement, automatic RF attenuation for extremely strong signals, and a comprehensive alphanumeric display of virtually all receiver parameters. Despite the automatic features available, the AR7030 is highly flexible. The operator can disable them if desired and be in full manual control. An infrared remote is supplied with the receiver, providing control over all commonly used functions.
A CONTROVERSIAL INTRODUCTION
I cannot remember another radio that generated so much positive and negative discussion at its introduction as the AR7030. Therefore a few comments are in order about the controversy surrounding the new AR7030. The internet newsgroup rec.radio.shortwave and Compuserve's SWL section in the Hamnet Forum have had many postings from both sides of the fence.
AOR introduced the AR7030 at the Leicester hamfair/electronics show last October, billing it as a "high dynamic range" receiver. The detailed information and specifications reported by AOR caused many to wonder if such commercial/military performance could really be reached by a consumer-grade receiver. When a price was announced by UK retailer Javiation, they wondered even more: ?799 within the UK, or ?695 to the USA including FedEx shipping. For British customers the AR7030 is less than half the price of a NRD-535.
AOR missed their initial Christmas 1995 release date by months, due to printed circuit board problems at a supplier. There were even (unfounded) rumors of legal action by Lowe Electronics against AOR. Although eight receivers were available on loan to reviewers in January, regular production did not begin in earnest until April. This delay encouraged skepticism even more.
The unusual design, small size and new features of the AR7030 also raised the eyebrows of those who prefer more traditional receivers.
However, a lively debate over statements in a Radio Netherlands' Media Network review,nd a more detailed technical explanation on Radio Netherlands:internet WWW home page: is what really fueled the controversy. The review presented test results with significantly poorer intermodulation-free dynamic range (IFDR) and 3rd order intercept point (IP3) figures than those claimed by AOR. The internet article also said that AOR's test method was non-standard, with a result of spurious "good" numbers due to AGC action reducing receiver gain. John Thorpe later countered with a letter on AOR's internet WWW homepage and rec.radio.shortwave that disputed the claims, saying the method is indeed standard and that the test equipment used for Media Network's review was not sufficient for proper measurement. Both parties have posted detailed information on their specific methods and equipment to support their position. It should be noted that the Media Network review concluded that the receiver is a good value in Europe with well above average performance in its price category.
Other reviewers and independent tests have produced figures comparable to AOR's specifications, including Chris Lorek writing in Ham Radio Today and Craig Siegenthaler of Kiwa Electronics. User-reviews in the Danish SW Club International Shortwave News bulletin and on Ray Woodward's internet WWW homepage also give the receiver high marks.
FEATURES & COMMENTS
This is a feature-laden set even though the receiver has a sparse front panel. The full details are available on AOR's internet home page and the main points have been covered in other recent reviews. From a DXer's perspective, a number of these are worth commenting on.
This receiver is apparently designed around the concepts of total control and information feedback. The menu system and dot-matrix display (discussed below) are critical to the AR7030's approach. A few examples are: passband shift settings displayed in 0.1 kHz increments, bass & treble adjustments shown in plus or minus decibels from a "flat" passband, dual audio outputs independently adjustable in audio level and displayed as a percentage of total output; volume and I.F. gain displayed as a percentage of total output, and the 100 memories which can contain the tuned frequency, mode, I.F. bandwidth, passband shift setting, scan include/exclude, squelch setting, and BFO setting for CW & DATA modes.
The AR7030 is an expandable and flexible receiver. Options and accessories can be properly integrated into the radio's control structure, rather than "tacked on" as an afterthought. The AR7030's operating system can also be customized for specific commercial or scientific applications, according to AOR.
Although my main interests are between 530 kHz and 5 MHz, I find it intriguing that the AR7030 tunes down to 0.00 kHz. The receiver's sensitivity is not reduced in the mediumwaves or below. Both the preamp and the 4-step attenuator are available for use if desired. The so-called "dawn chorus" and "whistlers"--natural radio phenomena at 15 kHz and below--can be tuned on the AR7030. These and other DXing targets in the VLF range are another part of the spectrum that can be pursued with this radio. Likewise, the 32 MHz upper tuning limit allows for a bit of lo-band VHF DXing during the summer months. (In past years from the Seattle area, I've been able to listen to Central American para-military communications and public utilities chatter from the East Coast, all between 30 and 32 MHz.)
A clear, backlit dot-matrix LCD display shows all receiver settings. Excellent use is made of a two-line display due to a carefully thought-out series of branching menus. The feel of DXing with the AR7030 reminds me of operating a laptop computer, such is the effect of the menus, the display, and the multi-function knobs and buttons. If it were not for this computer-like approach, the receiver would need numerous individual controls and a larger case. The receiver's price would also be higher!
Three definable "setups" allow the user to quickly jump between favorite parameters for the type of listening desired. AGC, filter bandwidth, mode, tone controls, RF gain, etc. can all be assigned to the setup memories. I have setup "A" configured for general SWLing, "B" for tropical band DXing, and "C" for foreign MW DXing.
Frankly, the menu system and flexible controls of the AR7030 may disenchant some radio hobbyists. Traditional design implies a single control for a single function, and a display or front panel that always shows the same information in the same spot! John Thorpe has given us a new approach. Using just a modest LCD display, the AR7030 can report virtually all receiver settings and intelligently assign "soft labels" to push buttons and rotary controls. The only controls with single, dedicated functions are the frequently used ones: the power switch, menu button, volume control, up/down mode buttons, the fast tune button and the main tuning knob. Those who are comfortable with computer software will quickly grasp the logic behind the AR7030's array of menus.
Efficient operation with the front panel controls only comes with experience and understanding of the menu structure; the key is learning which menus keep your favorite parameters accessible. I prefer the filter menu with the assignable rotary knob soft-labeled as "PBS" (passband shift). This gives me immediate, direct access to filters, passband shift, mode, main tuning, volume, power on/off, and fast tune. A further press or two of the filter button allows adjustment of AGC settings (fast, medium, slow, plus off) and tone. Other receiver functions are accessed through other menu selections, or directly with the remote controller.
Again, to some users this may seem to be an ergonomic nightmare. The AR7030 should be given a fair chance, however, as familiarity comes with practice. Fortunately the buttons have a good tactile feel to them, making quick changes easy. Those who cannot bear to operate anything that doesn't feel like the large, classic rigs of yesteryear will view the AR7030 as mere gadgetry. In my opinion it is not an unusual or difficult receiver to use, but rather fun to control after the initial learning curve.
FILTER MEASUREMENT AND ALIGNMENT
This is one of the unusual features of the AR7030, a capability it shares with the professional Racal RA-6790GM receiver. Many styles of MuRata ceramic filters (CFJ, CFK, CFW styles and others) plus Collins low-profile mechanical filters can be directly fitted. Other possibilities exist with Kiwa Electronics' Premium filter modules. The AR7030 will measure the bandwidth, determine the proper USB/LSB offset for each filter, and sort the filters in ascending order.
The sequence takes about 45 seconds and is interesting to watch. The resulting exact alignment is useful during ECSS tuning of an AM signal, as there is no change in audio pitch when alternating between USB and LSB (if the receiver is properly tuned beforehand). The AR7030 is the first receiver I've owned which does not exhibit at least a small amount of USB/LSB error due to normal variations in the manufacture of individual filters and receiver alignment.
The supplied bandwidths are nominally 2.2, 4.5, 7.0 and 10.0. Although four filters are standard with two optional filter positions, in reality any filter may be changed except the 10.0 kHz bandwidth (meant for narrowband FM). Any filter may be used in any mode. In my AR7030, these bandwidths are measured and displayed as: 2.0, 5.4, 6.4, and 9.5 kHz. The owners manual explains that most filters are named by their minimum passband and (if stated) their maximum stopband specifications. There can be variations from filter to filter, and even temperature of the filter affects the bandwidth. I've noticed a 0.1-0.2 kHz reduction in measured bandwidth of the filters in my AR7030 if I run the filter calibration routine after the receiver is completely warmed up (1/2 hour).
Kiwa Electronics' new "Premium Filter Modules" make an excellent addition to the AR7030's arsenal of filters. Hookup is simple, using miniature coax cable for input/output leads. All module circuitry is inside a fully shielded enclosure. A ground connection and 4.5 to 15 volts DC power (at 1 ma) is also required. These modules have ultimate rejection better than 100db; my particular 3.5 kHz (nom.) filter module measures 107db. This surpasses even the highly-regarded Collins mechanical filters. The shape factor is stated to be better than 1 to 1.8, typically 1 to 1.5 or 1.6. The modules are available in selected bandwidths in the approximate range of 2.5/2.7 to 8.0 kHz, and the price is $70 US. A late addition to Kiwa's PFM series is a printed circuit board that holds up to three filter modules.
I also have Kiwa's "High Performance Ceramic Filter", the CLF-D2K, made especially for Kiwa Electronics by MuRata. It is nominally a 3.5 kHz filter but displays as 2.9. In addition I've recently replaced the stock 5.4 kHz bandwidth with another Kiwa PFM module, which the receiver measures as 4.4 kHz. The total of six bandwidths in my AR7030 measure and display as: 2.0, 2.9, 3.4, 4.4, 6.4, and 9.5 kHz. The difference between the 2.9 and 3.4 Kiwa filters is great enough in practice to make each one a worthwhile addition to the AR7030.
AM SYNCHRONOUS DETECTION
This mode has the tenacity of a mountain goat and clings to signals weak and strong without problems. It is the best I've ever encountered, period. The passband shift can be adjusted liberally in synchronous AM (SNC) mode without causing squeals of complaint or loss of lock. Finally, a synchronous detector that a DXer can use! My ears cannot detect any rise in distortion in SNC mode (as reported in the Radio Netherland's review); in fact, audio sounds definitely better than with the AM envelope detector. With passband shift carefully adjusted, both Kiwa filters are very useful using this mode.
As with the Drake R8 and R8A, the use of passband shift with the SNC mode allows selection of either sideband (or any point in between). This is an extremely useful tool for avoiding adjacent-channel intererence and/or peaking certain audio frequencies to aid intelligibility.
The synchronous detector can be configured to use either a narrow, wide, or auto method of operation. Wide and narrow are "manual" settings; the user tunes the receiver until the receiver locks onto the carrier. Wide is easier to tune but cannot cope with selective fading as well as narrow can. The auto-synchronous method is an unusual feature that tunes the receiver automatically, locks onto the carrier, and displays the center frequency (normally with 30 Hz or better display accuracy). The AR7030 only needs to be tuned somewhere within the passband of the signal before switching to SNC mode. It's interesting to watch the receiver "think" a moment, tune up or down to the carrier, and then lock onto the station.
My test signal for synchronous detection with any receiver is Radio New Zealand International on 15115 kHz during my local evenings. It's often subject to annoying rapid fades after sunset. My Drake R8 would lose lock and "bend" musical tones unmercifully, but there's no such problem when using the AR7030. I have not heard it lose lock even once on this signal.
With the manually-tuned SNC methods, greater than ( >>> ) or less than characters are displayed, indicating which direction the receiver needs to be tuned in order to gain lock.
For unknown reasons, the auto-tune synchronous detector occasionally takes considerably longer than usual to lock onto a signal. The audio is heard uninterrupted in normal AM (envelope detection) while the receiver is "thinking". I've waited as long as 20 seconds for the AR7030 to switch to SNC mode. When it does, however, the result is rock-solid reception.
Go to Chapter 2