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- Published: Friday, 05 December 2003 00:00
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THE AOR AR7030: A BOLD NEW RECEIVER FROM BRITAIN
REAL WORLD PERFORMANCE
In early May I took delivery of my AR7030 via FedEx from the communications retailer Javiation in the UK. The 695 UK pounds price to the States (including shipping) worked out to $1052 US. The $54 invoice for the customs duty put the total at $1106, which is just a few dollars more than a Drake R8A in the USA. If one doesn't mind the risks involved with overseas purchases this is the way to go, as the cost from US outlets reportedly will be around $1300.
In the few months I've owned this receiver I have used i t at home in a suburban neighborhood setting and during two DXpeditions to the Washington State coast. The home location is a test of the AR7030's intermodulation performance when hooked up to one antenna in particular: a 350 ft. terminated, impedance-matched mini-Beverage. Although this antenna is on a 270-degree bearing toward Papua New Guinea and Irian Jaya (two favorite DX targets), it is also directly in line with a few mediumwave powerhouses.
The only instance of intermod I've discovered with this antenna and the AR7030 is weak garbled audio on 3260 kHz, which is the mixing result of my two most powerful locals: (2 X 850 kHz) + 1560 kHz = 3260 kHz.. Both of these completely "pin" the AR7030's digital S-meter (maximum display of S9+50db) on their primary frequencies. With Drake R-7 and R8 receivers I previously owned, these two stations would show a level of S9+60db. The 3260 mixing product doesn't raise the S-meter above the S-1 level band noise, but it is heard with audio from both 850 and 1560. Switching in 10db of attenuation, adding a high-pass filter, or changing to another antenna completely removes the intermodulation. The intermod is only noticed when both stations are using daytime power.
Both the Drake R-7 and R8 exhibited the same problem on 3260, so the AR7030 is not alone. So far I have discovered no other obvious mixing products--on any band--with the AR7030 at my home location. When I owned the R8 it had a few other problem frequencies between 2.0 and 3.5 MHz, and in the longwave region. With the AR7030 connected to lengthy, unterminated Beverage antennas at the coast, I find no indications of mixing products or other spurious signals on longwave, mediumwave or shortwave.
Since modifying the high-pass filter as described above, the intermodulation products on 3260 kHz are completely gone. This is now the first receiver I've used that can pass the "3260 test". Kiwa Electronics' measurements after the modification show an IP3 figure that varies by only a few decibels: +29 dBm to +34 dBm, from 500 kHz to 32 MHz. The average IP3 looks to be +32.5 dBm. If you do not want to handle this delicate modification yourself, Kiwa Electronics will do the work for $70 parts and labor.
LOW PHASE NOISE, HIGH AUDIO QUALITY
The AR7030 is clearly the quietest solid-state receiver I've ever operated. In a comparison with a Japan Radio NRD-525 receiver, the difference is dramatic. The low noise level is a revelation; and when used in a quiet setting with a good antenna you get the impression there is nothing between the signal, the atmospheric noise level, and your ears. The AR7030 seems nearly "transparent" as it goes about its business.
The best of the hollow-state receivers of the past could achieve phase noise figures of -160 dBc/Hz. With a measured phase noise of <-156dBc/Hz at 100 kHz spacing, my AR7030 is in the same range. This level of phase noise performance ensures minimal degradation of the dynamic selectivity of the receiver's I.F. filters. (This is a prime reason why Kiwa's Premium Filter Modules are a great addition to the AR7030.) Audio quality in all voice modes and bandwidths is very pleasant, reminding me of the sound from John Thorpe's HF-series of receivers. A bonus for DXers is the very useful bass and treble settings. There are no "do-nothing" knobs on the AR7030! Careful adjustment of the bass and treble helps intelligibility of weak, muffled stations such as the tropical band Indonesians.
During a DXpedition I made a comparison between the audio quality of a Drake R8 and the AR7030 on trans-Pacific mediumwave and tropical band stations (Solomon Islands 5020 kHz in particular). I used the same pair of headphones (Realistic PRO-25) and tried various bandwidths on each radio. The receivers sounded slightly--but distinctly--different. The R8's audio could be described as "clear and crisp" and the AR7030's as "smooth and mellow". Both receivers are easy on the ears and can be listened to comfortably for hours on end. Most importantly, each receiver provides good intelligibility of signals.
When bandscanning with the AR7030 it becomes apparent that selectivity is quite good. The best stock filter is the 2.2 (nominal) ceramic, and it's the filter of choice for serious DXing if no optional, higher quality filters have been installed. If all six filter positions are filled there are no less than ten individual I.F. filters comprising the I.F. chain (including "post-I.F." filters). This cascading of bandwidths results in very good adjacent channel rejection, even though most of the stock I.F. filters are inexpensive MuRata ceramics (such as used in low-cost portable receivers). The selectivity John Thorpe has achieved through careful circuit design and modest components is impressive. (A similar approach is used in the design of Kiwa Electronics' Premium Filter Modules.)
The above average filtering and the AR7030's passband shift control are highly useful for DXing mediumwave "splits". As an example, while listening to T3K1 Kiribati on 846 kHz, it was possible to avoid interference from a trong semi-local on 850 kHz by tuning in LSB and using the wide-ranging (+/- 4.2 kHz) passband shift. In my opinion the AR7030 provided better reception than a NRD-535D on this station. Even though the NRD-535D has the unique variable bandwidth control (BWC), that filter degrades in shape factor as it is narrowed. Also, the passband shift does not have an adjustment range approaching the AR7030's (the NRD-535D has a passband shift range of +/- 1 kHz). Because of different bandwidths in the two receivers, it was tough to compare the selectivity of the AR7030 against the R8A. The specifications would appear to give the AR7030 the edge. In actual use on foreign mediumwave and tropical band DX they both performed very well. More comparisons need to be done, but it appeared to me that the AR7030's stock filtering is at least the equal of the R8A. The extra Kiwa Electronics' bandwidths give a modest audible edge to the AR7030 when using those two filters in my receiver. Unfortunately, the R8A's filtering cannot be changed or upgraded because the bandwidths are composed of many individual and carefully-matched parts on the circuit board.
The cumulative effect of the cascaded filters results in very good performance even with the wider stock bandwidths. I've been surprised more than once by the usefulness of the stock 5.4 and 6.4 filters when coupled with passband shift and ECSS tuning. Even in the difficult mediumwave band the 5.4 filter is useable for DXing stronger trans-Pacific split frequency stations. The Kiwa PFM 4.4 module that replaced the stock 5.4 filter position in my AR7030 is an even better choice for stronger splits.
Despite the useful passband shift, occasionally some carriers or hets cannot be overcome (as with any radio); a notch filter would be welcome on the AR7030. An optional notch filter is expected to be available by August from AOR, and it may include a noise blanker feature. Now I'm using a Radio Shack DSP-40 digital audio filter strictly for its "auto-notch" capability. The DSP-40 works well for the purpose, and at a close-out price of less than US. $40, it was an inexpensive solution. Some Radio Shack outlets still have the DSP-40, now at a $30 price.
I do not find the current lack of a noise blanker to be a problem with this receiver. Still, I will likely add the noise blanker to my AR7030 when it's available, just to make the receiver complete. I prefer to tackle noise problems with outboard accessories such as the JPS ANC-4 Antenna Noise Canceller. With this approach the noise cannot affect the AGC of the AR7030, but the gain control of the ANC-4 should be used cautiously as its amplifier can be overloaded by strong local MW stations.
There are many small details that become noticeable and useful to the DXer as he spends more time with the receiver. The following are a few features that I consider "nice touches":
1) No immediate blast of audio in the AGC off position. The I.F. gain takes a couple seconds to reach 100%, so cycling through all three AGC speeds is gentler on the ears when the off position is reached.
2) The high-impedance antenna port and the ground connection for the AR7030 use a locking lever to engage the wire, rather than a spring-loaded pushbutton. I find it easier and quicker to use than the typical spring connector. A small detail to be sure, but it's appreciated when working around the back of the AR7030 in low light conditions or amongst a tangle of wires and cables.
3) The relay timer, the 24-hour clock, and sleep timer are easy to set and activate. I particularly like how the AR7030 displays both the current time and "TIMER ON AT 18:30" (for example) on the dot-matrix display when the receiver is on standby for remote recording. When the AR7030 is turned on for peration it can show the current 24-hour time, including seconds, on the display if desired.
4) Utility and HF aero monitors will enjoy the powerful scanning and squelch facilities. The receiver provides adjustable hold, delay, and mute, among other features. The squelch level can be set independently for VFO's A and B, as well as for each of the 100 memories. Scanning on HF has some real limitations, but the AR7030's independent squelch settings makes the most of variable conditions from band to band.
5) The bar graph S-meter is composed of 70 segments and is very accurate. I suspect that each S-unit (and intermediate step) is programmed into the AR7030's microprocessor, so that the meter will not respond until the proper signal level is encountered. Traditional analog S-meters are rarely linear and exacting across their entire range.
6) The excellent owner's manual is one of the best around, among contemporary receivers. Curiously it lacks the British colloquialisms found in other UK equipment manuals. It almost reads as if it was written by a US author. Particularly interesting are the discussions about the filter calibration routine and the automatic-tuning synchronous detector. Full technical details and a block diagram are at the end of the manual, but no circuit diagram.
AOR does not include computer control data in the owner's manual. The PC information is in a separate nine-page document . Because it's possible to accidentally scramble the data in the AR7030's microprocessor via computer, AOR is reluctant to widely publish programming information. This receiver is a major leap forward in PC control capability (even individual mixers and oscillators can be controlled by computer link). Careless programming can turn the AR7030 into an expensive and attractive paperweight! Interestingly, all commands to the receiver are byte structured in binary format, so it is not possible to control from a terminal.