The Iowa QRP Group Presents: 
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

Part 4--
WARC-Bler Parts List:
Quantity Part Marking
6 10.141 MHz Crystal 10.141 / Match Code
1 1000 pF Capacitor 102
3 100 pF Capacitor 101
4 120 pF Capacitor 121
2 33 pF Capacitor 33
2 27 pF Capacitor 27
3 330 pF Capacitor 331
1 6.8 uH Inductor Silver/Blue/Gold/Grey/Silver
1 0.82 uH Inductor Silver/Gold/Grey/Red/Silver
1 3.3uH Inductor Silver/Orange/Gold/Orange/Silver
1 8.2 uH Inductor Silver/Grey/Gold/Red/Silver
1 51 Ohm Resistor Green/Brown/Black/Gold
1 180 Ohm Resistor Brown/Grey/Brown/Gold
1 470 KOhm Resistor Yellow/Violet/Yellow/Gold
1 1.2 KOhm Resistor Brown/Red/Red/Gold
2 MPS5179 NPN Transistors MPS5179
7" Trifilar Magnet Wire
Parts Notes:

Six crystals are provided.  These have been matched for better filter performance.  A two digit code is written on the crystal.  The two or three crystals used in the transmit and receive filters, respectively, should have the same code.  The crystal used for Y3, the BFO, need not be matched.

Four inductors are included with the kit.  The WARC-Bler requires re-use of the original 6.8 uH inductor included originally as L1.  It will be moved to L3.  Replacements for the 6.8 uH inductor are available for $1 (shipped) from Twisted Pair Labs.

The new inductor color codes are somewhat faded, but given the known values, can be worked out.  Contact Twisted Pair Labs for assistance if the values cannot be determined given the color band information in the parts list.


The folowing parts from the Warbler kit must be removed or not placed:

C6, R7, R8, R11, R12, R13, R15, R16, R17, R18
R6, R8, R15, R16, R17
L1, L2, L3, --IMPORTANT:  Do not damage L1, 6.8 uH.  This part will be re-used.

Low Pass Filter:

For L2, wind 13 turns on the same T37-2 core supplied in the original Warbler kit.  For retrofits, remove 10 turns from the Warbler L2.

Place a 330 pF capacitor (331) in the C11 and C12 locations.  The Low-Pass filter has been modified.

(Physically the filter section should look the same as before, but just with the modified components listed above.)

Transmit Filter:

We're going to replace one component, C6, with three components.  It may look a little ugly, but the filter passband is flat when a proper match is used.
Twist one lead of each of the three components together: 33 pF, 6.8 uH and 100pF.  Solder the three leads together and trim off excess.  Don't take so much that the strength of the joint is compromised.  More can be removed after it's mounted.

Now, place the free lead of the 6.8 uH inductor in the C6 hole tied to the SA612. (This is the hole toward the "top" side of the board-- the top side being the side where the connectors are located.)  The other hole of C6 is filled with the free lead of the 100 pF capacitor.  (The "bottom" side of the board, toward the "NJ-QRP 9/00" writing.) 

Ground the 33 pF capacitor by soldering to the grounded lead of D1, located near C6.

A similar operation takes place in the former location of C8.  Twist together and solder a 3.3 uH inductor and a 100 pF capacitor.  Place the other inductor lead in the C8 hole tied to R6.  The 100pF lead goes to the other hole of C8, connecting electrically to Y2.  Place a 27 pF capacitor in the holes formerly used for R6.  Remember, R6 shouldn't be there anymore.  If it is, remove it.
Place a 100 pF capacitor in the C7 location.  Place the two crystals with the same match codes in the Y1 and Y2 positions.


Place the unmatched crystal in the Y3 position.  The BFO crystal will have a matching code written on it, but will likely not match any other crystals in the set.

Transmit Driver Amplifier:

Put an MPS5179 in the places for Q3 and Q4.  The pinouts for the new transistors identical to the 2n4401s they replace.  Put a 51 Ohm resistor in the holes for R8.

The 6.8 uH inductor for L1 is replaced by a 0.82 uH unit.  Verify that C10 is 330 pF.  Replace it with an (included) 330pF capacitor if necessary.)

Re-wind T1 with 6 turns of trifilar wire.  This is included in the Warc-Bler conversion kit.  Observe the same polarity used in the original Warbler.  To tin the enameled wire, form a solder ball on your iron and set the tip of the wire in the ball.  Wait for the wire to heat up.  The enamel insulation will begin to bubble and darken.  Slowly move the solder ball up the wire for the desired tinned length.  Clean the tip of your iron, and run your fingernails over the tinned leads.  Tin the leads a second time, and the tinning should be perfect.  Use of a higher temperature iron is helpful, but not required.  800 degrees F works well, as does a soldering gun.

Scraping away the insulation with sandpaper or a blade is also acceptible-- if you do not nick the wire while scraping!

Receiver Pre-amplifier:

Put a 33 pF capacitor in the C13 position.  Put the 6.8 uH inductor recyled from L1 in the L3 position.  Place a 470k resistor in the R16 position.  Place a 180 Ohm resistor in the R15 position.  Place a 1.2k Resistor in the R17 position.  Solder a 1000 pF capacitor in parallel with R17.  This is most easily done by using one of the small capacitors originally intended for C11 or C12 to the R17 leads on the bottom side of the board.  We've included a 1000 pF ceramic disc capacitor with the kit in the event the (fragile) monolythic caps don't survive the transplant.

Receiver Filter:

The same construction used in the transmit filter will be used again in the receive filter.  Twist together one lead of each of the following:  120 pf, 27 pF, 8.2 uH.  The free leg of the 120 pF capacitor goes in the C18 hole tied to Y6.  The inductor lead goes into the other hole, electrically tied to U2 pin 1.  The remaining free lead (27 pF capacitor) is grounded by soldering to the grounded pin of C108 on the top side of the PCB.
Populate the rest of the filter by placing 120 pF capacitors in the positions for C15 to C17 and the remaining crystals in the Y4 to Y6 positions.

This completes the hardware modifications for your Warc-Bler.

Tuning up:

It is necessary to have a calibrated 30m receiver or frequency counter to accurately set the Warc-Bler's BFO, which affects both receive and transmit.  It is very important to set this for at least 10.1465 MHz or higher in frequency so that the LO suppression is sufficient for FCC standards!

Power-up the Warc-Bler, terminate the output in 50 ohms, and place it in transmit mode with no audio drive (remove the audio cable).  Place the counter probe on U2 pin 7 and read the frequency.  Tune C3 to set the frequency of the BFO to 10146.5 KHz.  If using a receiver, a short antenna can be tacked to U2 pin 7 to aid signal pickup.  This is a buffered output and has no effect on the frequency of Y3.  Alternatively, attach the receive audio cable to the computer, and run Digipan.   In DigiPan, set the 30m band configuration to use 10146.5 KHz LSB, and select the 30m band.  Using a HF rig (attached to a dummy load nearby) to transmit a carrier on 10142.0 KHz using CW or AM, adjust the rig so the received carrier line lines up at exactly 10142.0 KHz.

Now, connect both audio cables, the RS-232 keying cable, and an antenna or dummy load.  Place the rig in transmit and advance the PC's line out audio to the point where output power or supply current begins to decrease.  Back off the input signal level so the drive is below the max level.  A simple DC milliammeter in series with the Warc-Bler power supply is sufficient as a tuning indicator.  Nominal input current at 13.8v is 300mA.

The Warc-Bler will produce about 2W at 13.5v and closer to 3W with a 15V supply.  It is good operating practice to rely on the signal reports of others when adjusting your transmit levels.  Don't splatter; be considerate of other ops.  Oh, and have fun WARCbling!!!

THE END RESULT... Pure WARCbling Joy...

NEXT:  Conclusion, Appendicies and Credits.

May 14, 2001
Jeff Woods/Fred Spinner
(HTML Conversion and drawings by Fred Spinner)