This page lists projects recently completed.

PSK31 and MFSK16

Proliferation of free Digital Signal Processing software has spawned a revolution in Amateur Digital Communications.   Two of the newest and most popular modes are PSK31 and MFSK16.  Both are based on PC Sound Card DSP software that is freely available on the Internet (see links below).  These modes are similar to RTTY in there is a 'live' QSO between operators using the computer and keyboard.  Both modes work well with low power and low signal levels.  In fact, low power is preferred with these modes.  To high transmitter power tends to overwhelm weaker signals within the receiver and software.  Communicating with the weaker signals is what these modes are all about!!!

Digital Signal Processing software for Amateur Radio relies on the sound card found in most PC’s.  The sound card’s output is connected to the radio’s microphone input via an interface.  The radio’s audio output is connected to the sound card’s line or microphone input.  The PTT function for the radio is usually accomplished by a RS-232 interface between the computer and the PTT circuit on the radio.  Raising RTS or DTR causes the PTT function to ‘fire’, which switches the radio into transmit mode.  The software does this automatically when necessary.  The sound card to radio interface is the function of the Rig Blaster product by West Mountain Radio.  This interface works well and is reliable.  In addition to the PTT via RS-232 function, the Rig Blaster provides a VOX function that keys the transmitter upon receipt of audio from the sound card output.  For Hams that prefer to build their own, several interface circuits are available.  The most common can be found at: http://www.qsl.net/wm2u/interface.html.  I have built and experimented with these home-brew interfaces and experienced leakage of RF from the computer into the radio causing de-sensing of the receiver.  Ferrite beads or some other RF choke may reduce this problem.

PSK31 is an acronym that stands for "Phase Shift Keying, 31 baud".  Signals occupy approximately 31 Hz of bandwidth.  There is no error correction, but that does not seem to be much of a problem with this mode.  PSK31 was invented by Pawel Jalocha, SP9VRC and Peter Martinez, G3PLX.  There are 2 'sub modes' of PSK31 operation.  Most common is BPSK in which the phase shift of the signal is 180 degrees.  QPSK uses a phase shift of 90 degrees.  This mode is faster and more reliable, although harder to tune.  Most QSO's use BPSK.

MFSK16 stands for "Multi Frequency Shift Keying, 16 Tones".  This mode uses 16 tones to create characters and occupies 316 Hz of bandwidth.  Communication speed is in the area of 64 bps or 15.6 baud.  MFSK16 uses Forward Error Correction so communications are reliable and tolerant of Doppler, multi-path and fading conditions.  This mode is based on old WWII communications protocols called Piccolo and Coquelet that were used by British Intelligence and other Allied services.

My first exposure to these modes was by building the PSK-20 QRP transceiver kit featured in a recent issue of QST.  The kit was easy to build and requires a minimum of tuning.  The kit can be purchased from Small Wonder Labs.  Any PSK31 DSP software can be used with this rig, however it was designed to be used with the DigiPan program.  This program is free and can be downloaded from here.

After obtaining an all mode HF rig, I added the Rig Blaster interface to the shack.  This component interfaces the radio with the PC's sound card with a minimum of problems.

My current favorite software is HamScope (again it's free!).  This software is the "Leatherman Tool" of Amateur DSP software.  It can drive a radio in PSK31, MFSK16, RTTY, ASCII and several sub modes.  It will even decode CW!!!

Digital Signals can be found starting at the following frequencies:

Links to Amateur Radio DSP software

All software listed runs under the Windows operating system.

Links to details about PSK31 and MFSK16

Tuna Tin II QRP Transmitter

The Tuna Tin II QRP Transmitter is a 400mw CW transmitter originally featured in the May 1976 QST and updated and featured again in the March 2000 issue.  I purchased the transmitter in kit form from the New Jersey QRP Club.  I found the kit easy to assemble, in fact the intent of this project was to practice kit construction in anticipation of more complex projects.  The transmitter is run with a straight CW key, a home brew 40meter dipole (soon to be replaced by a G5RV) and a Radio Shack (Sangean) short wave receiver.  

Dual Band J-Pole

Occasionally, I am the control station for the CARS Wednesday night net.  At the time,  I did not own a VHF or UHF 'base station', so acting as net control meant one of 2 things.  Either I was eaten by mosquitoes while running the net from my Miata, or eaten by mosquitoes while running the net with my H-T on my front porch.  To put the local blood-suckers on a AB4EZ free diet, I constructed a dual-band J-Pole antenna.  This will allow efficient 2m and 70cm communications from inside the house.  I reviewed several plans for J-Pole antennas, they can be found all over the Internet.  I ultimately used the measurements and guidelines found on the Copper Cactus web page, with additional input from the 2 meter J-Pole plans found in the ARRL handbook (1999 and 2000).  The antenna is now mounted to the roof of my house.  The 2 sections of the J-Pole are connected to a single RG-8 coax via an MFJ Enterprises duplexer with a MFJ surge protector added in for good measure.

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Revised: January 22, 2003.