Equipment Review
ASPiSYS ASMAX1 C-QUAM AM Stereo Transmitter
ASPiSYS - Athens, GreeceImagine our joy to actually see a professionally manufactured Part 15 AM Stereo transmitter. While there was once the Chris Cuff "Alfredo Lite" AM Stereo transmitter, the kit is no longer made available and it's power output was much lower than the allowed 100 milliwatts. While some folks have experimented with utilizing old AM Stereo broadcast exciters as the basis of their carrier current stations, an easy and affordable solution for the Part 15 broadcaster was missing ... until now!
We were aware of the ASMAX1 for quite some time. We had previously placed queries to the manufacturer some time ago while in the process of engineering a Part 15 station for a high school. The transmitter is a Part 15 compliant unit that contains a built-in C-QUAM AM Stereo generator. This was just something that begged us to check out. It only took 11 days for us to receive our evaluation unit from Greece.
Opening The Box:The ASMAX1 came well packed as it was delivered via the postal service. The transmitter comes without a power supply so you'll have to supply your own. The transmitter can accommodate power supply voltages from 13.8 to 18 volts DC, making it ideal for mobile applications. It will also run off your typical "wall wart" AC power adapter with the center conductor set for positive polarity.
The Inside Story:The exterior of the transmitter sports four front panel buttons that are used to control various functions on the transmitter. The 8 character by 2 line LCD display provides visual indications of system parameters. The rear panel of the transmitter is provided with two phono jacks for left and right audio inputs and one for RF output. There are two trimmer potentiometers for the audio input levels that are factory pre-set but accessible for user adjustment.
The transmitter construction is of high quality with a mix of surface mount and traditional semiconductors on the double-sided circuit board. The unit is a broadband design and there aren't any tuning capacitors required to tune the entire broadcast range. The transmitter has several jumpers that are factory configured for the particular version of the transmitter. While the audio pre-emphasis jumpers may be changed by the user, others jumpers are dependent on factory configuration and damage may result if they are changed by the end user. While the Part 15 compliant version of the transmitter is evaluated here, there are other versions of this unit with different power and frequency ranges for non-US users.
The LCD screen allows the operator to access functions and stereo / mono transmission, frequency selections, RF output on and off, clock calendar as well as the daily and weekend schedule. The ability is being able to program the transmitter's on and off time is a great addition to those who may want to use the unit in a remote location. Besides the stereo transmission ability, the programmable transmission schedule is unique to this transmitter.
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