ASMAX2 is a C-QUAM compatible Stereo, or Mono capable AM
Medium Wave DDS-based (better than PLL stability) radio
broadcast board for educational or similar use that offers
great audio quality, 1KHz frequency step selection (for
both 10KHz US and 9KHz EU steps) using only four keys. You
connect left-and-right audio and send it wirelessly using a
whip antenna, distance varies with surrounding conditions,
RF PEP output 100mW [according to US FCC Part 15.219] or
600mW PEP [EU] (at 50 Ohm) maximum over the entire band.
FULL BROADBAND DESIGN, no variable caps to adjust! RF power
adjustment is done via the keypad (no trimmer). Reception
is either on a regular AM radio (mono) or a stereo C-QUAM
compatible radio set anywhere from 530KHz to 1700KHz
(special model available for 510-2000KHz covering 160m
band) and minimum step of 1KHz.
It has two independently adjustable audio inputs, for Left
and Right channels with modified 50usec or 75usec
pre-emphasis and low-pass filtering (depending on
You can change the broadcast frequency, stereo/mono mode,
and other functions using the settings menu. After ENTER is
pressed the DDS is re-programmed with the new transmission
frequency. The power-on frequency and all other settings
are saved to the built-in non-volatile memory when exiting
the settings menu.
ASMAX2 is an upgraded version of the older ASMAX1 with
several enhancements and improvements, some of them being:
better stereo separation up to 40db, clearer audio and RF
signal, left-and-right mono audio component output to drive
a high-level modulator circuit (if needed), RS232 TTL level
port (TX, GND, RX) for complete configuration of all
parameters from a PC terminal. To do so, you need either
an RS232 level translator adapter (example:
). You can also
use an optional external Ethernet module to connect it to
the Internet for remote management from anywhere in the
The firmware is periodically improved and/or enriched with
additional features. The latest firmware can be found here:
For the 20x4 LCD model:
Board ASMAX2 firmware
For the boxed 8x2 LCD model:
Boxed ASMAX2 firmware
For other variants or custom configurations, please contact
One important enhancement is that on the LCD you can see
the real-time modulation percentage and bar-graph, giving
you the possibility to correctly adjust the final
modulation of the transmitter to keep it within specs, and
avoid over-modulation peaks that may lead to distortion.
The unit meets all FCC Part-15 requirements for AM
transmitters. It has an excellent spectral purity with
harmonics rejection better than -50dBc (upper half band) as
can be seen in a Spectrum Analyzer, out-of-band spurious
output better than -60dBc, and accuracy of the lock-on
frequency better than +/- 0.5Hz. You can manually turn the
RF output on/off, or use the built-in real-time clock to
set a daily or weekend schedule for automatic on/off at a
specific time. With this option, one can leave the unit at
a remote site and have it operate only for the specified
A C-QUAM Stereo encoding system is built-in and provides
crystal clear audio up to 15KHz and with a channel
separation of up to 40dB. Optionally, stereo encoding can
be de-activated via a menu selection in case you need to
use the device as a Mono AM transmitter.
The board is also capable of DRM transmission by selecting
the appropriate mode and using appropriate (PC) software
for the independent I and Q base band encoded signal.
For more info, please contact us.
The device requires 13.8VDC (FCC compliant USA model),
24V (EU/International) @350mA maximum.
Disclaimer: Although this unit meets FCC Part 15
requirements for AM transmitters, this does not mean it has
been FCC certified.
Available as board with 20x4 LCD.