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A STAND ALONE
HF SSB Software Defined Radio
Building on previous work, this radio is
the culmination of exploring FPGA for HF SSB radio design and
implementation over the past years. The main difference between this radio and
the previous versions is that it is based on relatively inexpensive
“evaluation boards“ which are
available from Linear Technology, Xilinx, and Analog Devices.
The radio is “stand alone”
in that no host PC is required for its operation. All of
the signal processing, from audio to RF, is done with an inexpensive
Xilinx FPGA. The user interface is implemented with a PIC processor from MicroChip.
Adding an RF power amp, low pass filter,
tuner and T/R switch produced fully synthesized HF SSB / CW transceiver.
Have a look, this is cutting edge!
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A Five Band 30" Diamond Loop
Antenna
This note describes a loop antenna in a
diamond configuration, 30 inches on a side, covering from 14 to 30 MHz. The
antenna is made from ½" copper pipe and can be disassembled into
sections for easy packing. On the air comparisons indicate that the loop
performs nearly as well as a full size dipole if the dipole is placed at
the modest elevations typically attainable during portable operation.
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A Loop Antenna Covering 7 to 30 MHz
This note describes a relatively small, but
efficient, loop antenna initially created for portable operation. With
suitable modifications, it can be adapted for fixed station use. In this
age of CC&Rs, an antenna similar to this may
very well be the answer to your problems. Have a look, be inspired, get out
the torch & soldering iron and create your own version!
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A Contemporary Homebrew Transceiver
with a Vintage Flair
Blending a few vintage components with a
major dose of today’s silicon produced this all band SSB/CW
transceiver.
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Curing KWM-2/2a IF Feedthrough
The Collins KWM-2/2a transceiver is the
precursor to all contemporary hf transceiver
designs. Between 1959 and 1979, well over 30,000 of these units were
produced by Collins Radio 1 , and many are still
in service today. Great care was taken to minimize spurious emissions from
the transmitter. The receiver however, has poor immunity to signals within
the range of the tunable IF. This note discusses the causes for the poor
receiver performance, and provides a solution by way of an optimized
passive LC filter. The filter can be constructed, adjusted, and tested
without modifying the transceiver.
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Using a Network Analyzer for the
Measurement of Q
Directly measuring tuned circuit Qs over
100 is difficult at best using RF Network Analyzers. However, by using a
small loop,
loosely coupled to the tuned circuit being measured (parallel
LC or cavities), good measurements can be made of Qs exceeding 1000.
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High
Q Measurements with an RF Bridge
With proper precautions, the
venerable General Radio 1606A RF Bridge has been found to give accurate,
reproducible, results for high Q measurements. The measurements are in good
agreement (e.g. Q=830 vs. Q=850) with those obtained using an RF Network
analyzer and a coupling loop.
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An
HF SSB Software Defined Radio
Now here is a VERY interesting radio!
The core of the processing is done with a Xilinx Field Programmable Gate
Array and a TI C6701 DSP. Add a small amount of analog stuff (RF amp,
RF power amp, low pass filter, T/R switch )
and behold, a fully synthesized HF SSB transceiver!
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