1.6. Philosophy of design
With the Model 539 Argonaut VI, Ten-Tec
has created a QRP transceiver combining
simplified controls and ease of operation with
the excellent performance of a low first IF
ham-band architecture in a compact, mobile-
friendly structure. The analog portion of the
radio is double conversion with IF
frequencies of 9.0018 MHz and 22.5 kHz. A
third conversion to zero-frequency IF is
accomplished in the DSP processor.
Refer to the Block Diagram in the
“
Specifications”
section for the following
discussion. Receive signals are routed to a
T/R switch at the input of the BPF/Preselector
board. This board also contains the bandpass
filter selected for the band in use and a
switchable 12dB receive preamplifier. On the
TX/RX board, output from the preamplifier is
mixed with the first Local Oscillator to
9.0018 MHz and routed to one of the three
roofing filters. After selectivity roofing, IF
amplification is provided by a variable gain
amplifier which also develops the high-level
AGC. Finally, the 9.0018 IF signal is mixed
with the second LO to develop a 22.5 kHz
low IF for the Signal Processing Unit (SPU).
Based on a 36.096 MHz temperature-stable
reference, the Oscillator board generates first
and second LO's with a DDS circuit and fixed
frequency division. The SPU samples the low
IF at 96K samples per second and applies the
resulting data to a digital signal processor.
Numerical algorithms running in the digital
processor accomplish additional selectivity
filtering, low-level AGC, and demodulation.
The resulting audio appears at the speaker and
line outputs.
The PIC processor in the front panel CPU
module executes firmware stored in
EEPROM to perform housekeeping functions
such as synthesizer programming/tuning,
signal switching, and front panel display and
control input. Based on the control inputs
from the front panel (or remotely via the USB
interface), the CPU writes display
information, tunes the LOs, adjusts
selectivity, and chooses both receiver
detection and transmit emission modes.
Transmit operation is basically the reverse of
receive. Audio or CW signals are generated at
zero-frequency (baseband) in the DSP,
frequency-shifted to the 22.5 kHz low IF, and
output to mixers on the TX/RX board for
conversion to the operating frequency. The
signal then travels in the reverse direction
through the selected Bandpass Filter to the
low-level drivers and Power Amplifier, then
finally through the Lowpass Filter to the
antenna.
The Argonaut VI is designed to cover the
following hambands:
160M - 1.795-2.005
80M - 3.495-4.005
40M - 6.995-7.305
30M - 10.095-10.155
20M - 13.995-14.355
17M - 18.063-18.173
15M - 20.995-21.455
10M - 27.995-29.705
539 / Argonaut VI Users manual
Release 0.10 – November 13, 2012
Part #74479
Printed in USA
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