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
Jeff Woods W0ODS, Fred Spinner W0FMS, and the Iowa QRP Society are proud to present for your "Warbling" enjoyment:
The 30M WARCbler Conversion Kit. (Available
at Dayton! In cooperation with the NJ-QRP Club) Turn
your low frequency PSK-80 "magically" into a DX "hound" 30m RIG!
1. Power Output on transmit is OK now. A solid 2W out. We determined that for good IMD performance (important on PSK31) that the power level needs to stay at this level. Here's some logic: a 100W rig generally is cleanest at 25W on PSK-31. The finals on the PSK-30 WARCbler are capable of a 8W max output. 8 times 25% = 2 Watts clean output. QED. Admittedly, the driver stage was an absolute bear to redesign and get working, and several computer models were generated, and many pads were lifted on the prototype unit to get it to fly!
2. Our solution of widening the TX filter's BW to 2900 Hz while leaving the RX filter's BW at around 2500 Hz works fine if proper attention is made to adjusting the LO frequency to at least 10.1465 MHz. This allows enough "slide space" that the crystal varations should be transparent to the builder/user, AND that the LO suppression is >35 dB from the desired PSK-31 signal. We could write a book (or at least an article) about the SA-612 mixer and it's relatively poor carrier suppression, and some of the disadvantages (remember: the main advantage is the low cost and complexity of this design-- it still is true and applies!) of the direct-conversion design for SSB or PSK rigs. Maybe we will write an article some day about this.....hmmm....
Conversion kits are done, and available.. we
have 30 kits... more can be ordered, lead time is 6 weeks.
Part 1 -- Introduction & Why 30M?
Part 2 -- Redesign of the Filters.
Part 3 -- Other Circuit Modifications.
Part 4 -- WARCbler Conversion Kit/Parts List/Conversion Instructions
Part 5 -- Conclusion