The 30M WARCbler PSK-31
Rig Conversion Kit
By: Fred Spinner, W0FMS and Jeff Woods, W0ODS
(C) Copyright 2001, Fred Spinner and Jeff Woods -- All Rights Reserved
May 14, 2001
A few months back, Fred W0FMS had built a Small Wonder Labs PSK-20 rig, and has had good luck with it. At the time the question was posed, "Wouldn't 30M be a good band for a PSK QRP rig?" Well, the answer, of course was "Yes!", but at the time it was not obvious how this could be done at a reasonable cost with reasonable performance.
More recently, the New Jersey QRP rig introduced another more simplified PSK-31 QRP rig, the "PSK-80 Warbler"-- also designed by Dave Benson, NN1G of Small Wonder Labs. This rig is designed for low cost and simplicity. It literally is a direct conversion receiver with the narrow crystal lattice (Cohn) filters placed at the operating frequency for selectivity. At $45, the rig is a BARGAIN.
One interesting design "limitation" that we noticed was that in both the PSK-20 and the PSK-80 rigs, there was a requirement to use only standard "microprocessor" or "colorburst" crystals since custom crystals were expensive to have made. Well, this is true until you reach about 100 crystals. At this volume, the crystals are only few dollars each, and the crystals are made in China!
In a fit of impulse, Jeff W0ODS and Fred W0FMS, decided that since over 500 of the NJ-QRP PSK-80 Warblers were sold, and each rig took 6 crystals a piece, that we should order 125 crystals to redesign the PSK-80 to the 30m band. The rest is history... The result? When the kit is finalized in the next couple of weeks, the conversion kit will cost between $25 and $30ppd/USA. Worst case for a cool 30m QRP PSK-31 DX rig is $75 (plus the case). This is quite reasonable for a rig of this caliber.
Small Wonder Labs: http://www.smallwonderlabs.com
Why 30M? Why 10.142-10.145MHz?
For those of you familiar with the characteristics of HF propagation, or simply those of you who listen to WWV at 10 MHz often, you should be familiar with the DX performance in that section of the HF spectrum. The 30m band is a long-haul DX band in most circumstances-- good propagation is achivable in both the high and low parts of the sunspot cycle. It is also only a CW and data band by law, and in our opinion 30m is underutilized by amateurs. (Nice and quiet? Maybe not for long! :-) )
The choice of the 10.141 MHz series resonant crystals was to make the rig operate in the 10.142 - 10.145 MHz segment of the 30m band, as is compliant with the current bandplans for IARU regions 1, 2 and 3. Although the "standard" calling frequency is a little lower, and 10.140 MHz is a popular frequency in the US and Region 2, we decided that following the bandplan worldwide was important, and also hope that we will carve out a little "QRP" window with this rig.
NEXT: Redesign of the Cohn Crystal Lattice Filters