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Ultra Comshack 64 Duplex/Simplex Controller

73 Review by Jeffrey Sloman NIE WO

The AEA PK-900

State-of-the-art digital ham radio.

Number 8 on your Feedback card

Advanced Electronic Applications, Inc.

RO, Box C2160 2006 196th St SW Lynnwood WA 98036 Telephone: 800-432-8873 Price Class: $569

Photo A. The AEA PK-900.

The dual-port PK-900 represents the next evolutionary step in AEA's multimode controller technology. Unlike the revolutionary OSP-2232, the PK-900 uses traditional modem technology with a few high-tech twists. The PK-900 offers improved ease of use and some changes in the computer-controlled portions of the unit's circuitry,

LCD City

Unlike previous models—even the top-of-the-line DSP-2232—the PK-900 sports a sexy new LCD annuciator panel in place of the traditional LED Christmas light display. This high-contrast, backlit panef is easy to read under most lighting conditions, (with the exception of some occasional glare from reflected light.) One thing that makes this new display particularly useful is that unlike the LED arrays of previous models, these indicators say just what they mean, The operating mode of either port can be seen from across the room—no more memorizing LED locations or guessing. The display provides a lot of information: operating modeT link state, TX and DCD indicators, various status indicators and, at the bottom of the display, a tuning meter.

Those of you interested in HF modes have, no doubt, spent a lot of time in front of your controller's tuning meter trying to get those LEDs to look just like the picture in the manual. I have, too. To be honest, my first reaction to the new LCD version was not good. It is quite different to use than the LEDs 1 had come to know. But after I had used the 900 for a while 1 found the LCD just took some getting used to. It is at least as good, if not better than, its predecessor. At the very least, it is physically wider, making it easier to see.

Note that the 900 display has only fixed annuciators, it does not have the ability to display arbitrary text messages like its DSP-2232 big brother. While this would be very nice to have, it really does detract from the 900Ts utility.

Also located on the front panel are the traditional threshold control (a nice, big, easy-to-use knob) and the power switch. This knob adjusts the sensitivity of the DCD (Data Carrier Detect) function, and is oniy functional for port 1, Moving the power to the front is a nice change from the PK-232, the 900's predecessor

The Back Panel

The back panel of the unit is a pleasant blend of the old and new. The 900 uses the same coaxial power connector as previous models, making upgrading a little easier. A five-pin DIN connector provides output for a tuning scope, and for direct CW keying.

This connector replaces the old RCA jacks for keying, although I'm not sure this is an improvement. The RCA approach was very easy to use.

The two radio ports depart from the PK-232 and more cfosely resemble the DSP-2232ls five-pin DIN connectors. The 232's unusual radio connectors made building a cable somewhat difficult once the AEA-supplied units were exhausted. A pleasing throwback to the 232, however, ¡is the inclusion of two 1/8-inch phone jacks on the rear for audio input. This is great for SWLs who will not transmit with the unit, and for those of you who are like me and just can't wart to see the unit do its stuff.

A fourth DIN connector provides FSK (Frequency Shift Keying) outputs for RTTY fans with radios capabie of using them. Both positive and negative keying are available. Transmit level controls for each radio are screwdriver adjustments, also located on the back panel.

The connection from the PK-900 to a data terminal or computer is made through a DB-25 connector which supports pins 1 through 6 and 20. These are the standard pins needed for any sort of RS-232 serial connection. Next to this connector is the unit's reset button, which operates in conjunction with the power switch to reset the 900 to factory defaults.

Four additional trimmers located on the right side of the box allow screwdriver adjust ment of the AFSK levels for each radio. The PK-232 had only one, pointing out that the 900 is a true two-port unit, not just able to switch between radios.

What Can ll Do?

The specifications of the PK-900 are impressive. The unit will operate in just about any mode that a modem ham could want: AX.25 (Packet) HF and VHF Baudot RTTY ASCI) AMTOR PACTOR

Morse (send/receive)

HF Wefax (Weather Fax) in Greyscale

NAVTEX reception

TDM (Time Division Multiplex) reception Bit-inverted RTTY (encrypted) reception The PK-900 accomplishes all these modes with some very nice hardware, AEA has always been known for superior HF performance, and the PK-900 incorporates the same eight-pole Chebychev bandpass filter used in the excellent PK-232 for high frequency operations. This filter means that the 900 should do much better than average with poor signal conditionsh an assertion bome out by experience—not just mine; ask around. The 900 has it all over the PK-232 in the modem department, since soft selection of the modems let each mode's precise needs be accommodated.

On the output side, the unit uses a DDS chip (Direct Digital Synthesis) to modulate the radio making it extremely flexible- The PK-900 could produce any sort of modulation you might want, including DTMF or two-tone sequential paging, if the mood struck you. A user program capability makes this feature

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