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100-channel scanner for home or mobile use Last June, we reviewed the AR900, a 100-channel handheld scanner manufactured by AOR in Japan. Now AOR has produced a mobile version, the AR950, which covers the same bands. By GARRY CRATT It is pleasing to see that after our review of the AR900, AOR has taken some of our comments to heart and made several important improvements to the design. First, the AR950 receiver produces significantly more audio which is a necessity for mobile applications. In addition, there is provision for an external speaker to be used, further enhancing mobile operation. Other improvements have been made to the instruction manual (which is now easier to read) and to the receiver squelch action, which 8 SILICON CHIP suffered from "popping" in the first AR900 sample submitted for review. Basic functions The basic functions of the AR950 are the same as for the AR900 handheld unit. There are 100 channels available for user selected frequencies and these are grouped in 5 banks (each of 20 channels). Each bank is labelled A to E. Banks can be added or deleted from the scan list by pressing the relevant bank key. These keys operate as a toggle. When the band has been selected for inclusion in the scan list, the relevant letter is displayed in the LCD panel. When the bank has been deleted, the letter disappears from the display. Frequencies to be scanned can be directly entered into memory while frequency bands are being searched. This is quite a useful feature because it allows a particular band of frequencies to be searched and when an interesting signal is found, it can be located in any of the 100 memory channels. The advantage of having 5 banks is that frequencies of similar interest can all be stored in the same bank. For instance, all aviation frequencies can be stored in one bank while mar ine frequencies can be stored in another. It is then quite easy to scan 20 frequencies relating to the same service. In ad- dition to the aviation and VHF marine bands, other bands of interest include the VHF or UHF amateur band, the UHF commercial band, the UHF CB band, and the cellular telephone band. In addition, the AR950 has a "priority" function which allows a user programmable priority frequency to be toggled while scanning a bank of frequencies. It also has a "lockout" function which allows unwanted channels to be bypassed during scanning, and a "hold" function which disables either the scan or search functions once a transmission has opened the receiver squelch. One of the more important and often overlooked features of such a scanner are the scan and search increments. The AR950 has increments of 5kHz, lOkHz and 25kHz on VHF high and low band; 12.5kHz and 25kHz on the airband, UHF bands, and trunked 800-900MHz bands; and 30kHz on the cellular telephone bands. This should cover all frequency allocations on all bands! Another plus for this particular scanner is the use of EEPROM (Electronically Erasable Programmable Read Only Memory) technology which means that there is no need for nicad batteries to back up the frequencies programmed into memories. With EEPROM technology, all data programmed into memory is stored until it is updated or deliberately deleted by the user. Even if the power source is removed, the frequencies in memory will be retained. Antennas The AR950 is supplied with two antennas, one of which is a dedicated 800-900MHz ¼-wavelength whip for improved reception of the trunked radio and cellular bands. These bands are becoming increasingly popular with scanner enthusiasts and radio technicians alike. The other antenna is a telescopic whip which is designed to cover the VHF bands. Most fixed point or "home" installations will, of course, use an external antenna such as a discone. Because of this, the AR950 has an inbuilt switchable 20dB attenuator for use when strong adjacent channel signals are present. During testing of our sample, we experienced interference of this type from four Sydney television transmitters which are located within 1km of our test laboratory. Switching in the attenuator reduced this interference to a level which allowed us to set the squelch so that all desired channels were received without problems. Protect Your Electronic Equipment & Valuable Data Files from a Power requirements The AR950 operates from 12V DC and is supplied with a polarised power lead with inline fuse. Also, the unit has an inbuilt series diode to prevent possible damage from reverse polarity of the power supply. One criticism we do have of the unit is that, when placed on a flat surface (such as a desk) and when viewed from above, the LCD is a little difficult to read. If the unit is tilted upwards by raising the front edge by 25mm or so, the problem disappears. A simple wire stand would have cured this problem but this seems to have been overlooked by the manufacturer. Despite this shortcoming, the AR950 represents good value for money at the recommended retail price of $399, especially when the country of origin (Japan) is taken into account. The unit is distributed by Access Communications, 33 Alleyne St, Chatswood, NSW 2067. Phone(02)417 5311 for the name of your nearest dealer. ~ With COMPUTER PROTECTOR A definite must for all electronic office equipment Available in the folloWing Current Ratings: I Amp, 3 Amp, 6 Amp, & I O Amps ..------Cl.l'l.l:IJJ ■ ~ ~5!Lng~se I SYSTEMS Wanted: Your Circuit Ideas Have you got a good circuit idea languishing in the old brain cells? If so, why not send it to us for publication in Circuit Notebook? We'll pay up to $70 for a really good circuit, depending on how much work we have to do to knock it into shape. So transfer your idea to paper, write a brief circuit description and send it to SILICON CHIP, PO Box 139, Collaroy Beach, NSW 2097. WESTINGHOUSE BRAKE & SIGNAL COMPANY (AUSTRALIA) LIMITED SIGNAL DIVISION 80-86 Douglas Pde, Williamstown. Victoria. (PO Box 267, Williamstown. Victoria 3016) Phone (03) 397 1033. Fax (03) 397 1861 Telex: 37 477 Wessys Vic (03) 397 1033. NSW (02)5451322, Old (07) 275 3188 SA (08) 212 3161 , WA (09) 446 8844 COM/1 JULY 1990 9