Swan is backt After a several year hiatus, during which little was heard from the company, Swan has returned to amateur radio with an impressive array of all-new, state-of-the-art equipment.
Swan, for those who have short memories, was a dominant force in amateur gear in the late '60s and early 70s. I was one of thousands of young hams of that era who yearned to own a Swan rig, but my high school and college finances never gave me that opportunity. That's one reason I jumped at the chance to put one of Swan's new breed, the Astro 150 SSB Transceiver, through its paces,
The Astro 150 bears scant resemblance to the transceivers of that earlier time. If you haven't shopped for an allband rig in the last five or ten years, you'll be amazed at just how compact and convenient they are.
The Astro 150 is a five-band SSB and CW rig covering 10-80 meters, A sister model, the Astro 151, covers 15-160 meters. The frequency coverage on each band extends well beyond the upper and lower limits of the amateur allocations, making the 150 a fine choice for MARS operation. With the bandswitch in the 20-meter position, for ex^ ample, the transceiver tunes from 13.8 to 16.0 MHz. The other bands offer a similar overlap.
While the 150 is designed for SSB and CW operation, the owner's manual advises that SSTV and RTTY operation is possible if you take precautions. It recommends providing a small cooling fan for the heat sinks of both the transceiver and its power supply. In addition, the mike gain control should be used to reduce output to 50 Watts or less. A rear panel RCA jack is provided for inputting AFSK or SSTV signals.
Inside the 150
This transceiver is a ruggedly
built modular rig. Virtually all components, including most of the front-panel controls, mount on printed circuit boards. Connections between the boards are mostly of the plug-in variety, so removing a board for service should not be difficult. A profusion of heavy metal brackets and plates provides rf shielding as well as mechanical rigidity. My lone reservation about the construction of the 150 is that a few of the metal brackets inside the rig have sharp edges which might erode the insulation on nearby wires. Admittedly, this is a minor point, as an enormous amount of abuse and vibration would be necessary for such damage to occur, A couple of well-placed pieces of plastic tape would set my mind completely at ease. Unless you plan extensive mobile and portable operation with your Astro 150, it is not cause for concern. This rig will last.
Despite its small size (3,75" H x 9.75" W x 11.75" D), the 150 weighs in at a hefty 13 pounds. The companion PSU-5 Power Supply/Speaker is of similar size. Both the transceiver and its power supply have their own on-off switches, a nice feature for those who donl like to connect a "hot" lead to any piece of equipment.
With few exceptions, there is no shared circuitry between the receiver and transmitter. The receiver is a single-conversion design with a 9-MHz i-f. The claimed sensitivity is ,35 uV for 10 dB (S + N)/N. For CW operation, a 300-Hz i-f filter can be selected, or you can opt to use the SSB filters.
The transmitter is of a broad-banded design with an output power of 100 Watts PEP. As with most "no tune-up" transmitters, a law swr is important. The 150 will perform up to specifications only if it is operated into an swr of 2:1 or better. At higher ratios, the transceiver protects itself by automatically reducing output power so that the final transistors do not overheat. For this reason, Swan recommends using an antenna tuner to keep the swr, as seen by the transceiver, as low as possible.
The 150 offers full break-in (QSK) on CW, something found on few rigs at any price these days. Break-in is accomplished by leaving the final amplifier always connected to the antenna through the low-pass filters. In the receive mode, the final power transistors are biased off, effectively creating an open circuit on the transmitter output transformer. The receiver input is coupled to the secondary of this transformer via a highspeed reed relay.
Perhaps the most unique technical feature of the Astro 150 is its method of frequency selection and tuning. This transceiver is one of a small handful of amateur HF rigs incorporating true digital frequency synthesis. Much of our 2-meter equipment (and even some G8 gear) has used synthesizers for several years, but only recently has it become available in multiband HF radios.
incidentally, just because a transceiver has a digital display, this does not necessarily mean that it's synthesized, in many rigs, the operating frequency is determined by conventional vfo circuitry, and a frequency counter is used to produce the digital display. The principle of synthesized frequency control Is completely different, as we shall see.
Swan's design uses a pair of phase-locked loops (PLLs) to provide precise crystal-controlled reference frequencies to six voltage-controlled oscillators (vco's), Five of these are designated as "band" vco's, The outputs from the band vco's are divided by a diode-programmed divider so that band vco frequencies are variable in steps of 500 kHz, The transceiver's bandswitch selects the proper vco and diode program for each band. The 7-32-MHz output of the selected band vco is summed with the 5-7-MHz output of the sixth or "tuning" vco to produce a local oscillator frequency in the 12-39-MHz range. The local oscillator is thus always about 9 MHz above the operating frequency, and indeed, the Astro 150 uses a 9,0165-MHz i-f.
Directing traffic inside the synthesizer is an 8048 micropro cesser chip, a device from the same family as the popular 8080 chip found in thousands of microcomputer systems. A small amount of read-only memory stores a program containing the instructions which allow the 8048 to control this complex radio-
The microprocessor accepts as inputs the band and mode you have selected, along with signals from the tuning controls, It uses this data to produce signals which determine the frequency of the tuning vco. The 8048 also sends the proper information to the readout board to enable it to display the correct frequency. The microprocessor and Its program also carry out other functions which would otherwise require much additional logic. For example, as long as power to the 150 is not interrupted, the microprocessor will remember the last frequency used on each band. If you want pileups on five different bands simultaneously, the Astro 150 can do it!
With this high-technology frequency-determining scheme, you wouldn't expect the 150 to
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