Thanks SW40+ Manual
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Instruction Manual The “Small Wonder - 40+” 40 Meter Superhet Transceiver Kit Thanks! For purchasing one of the Small Wonder Labs “SW-40+” transceiver kits. This kit is an updated version of the classic ‘40-40’ transceiver board which originally appeared in the November 1994 issue of QST. Please take a few moments to look over the section entitled “First Things First”. This is background information in case you’re fairly new to homebrewing or kit-building. Please – Be sure to read through the “Building Instructions” portion of this manual before you fire that soldering iron up! That section contains useful information which is important to your success with this kit. TABLE OF CONTENTS First Things First ........................................... 2 Materials........................................................ 4 Parts List........................................................ 4-5 Theory of Operation ...................................... 6 Schematic ...................................................... Pictorial Drawing .......................................... 7 8 Building Instructions ..................................... 9-11 Wiring the “SW-40+”.................................... 12 Alignment...................................................... 14 Troubleshooting the “SW-40+” .................... 15 Troubleshooting Values ................................ 17 D. Benson, K1SWL Small Wonder Labs 2/9/2007 1 THE FINE PRINT There are lots of small parts in this kit. With many of us getting older, this may prove troublesome. I highly recommend a magnifying glass or close-up glasses to check all solder joints and component codes. THE OTHER FINE PRINT You should be familiar with the standard colorcode markings on resistors. If not, Radio Shack’s Color-Code Guide, #271-1210, will help. If you’re not sure, verify the resistor values with an ohm meter. Resistor color codes are given in the parts list. For what it’s worth, approximately 8% of the male population is red/green colorblind. If you’re one of these, you should be verifying all resistors with a meter before installing them. Despite the care I’ve put into this manual, it may contain the occasional error. In the event of a conflict between portions of this manual, the following order of precedence applies (most trustworthy first): Schematic Pictorial Parts list Everything else Soldering skills: By all means, let me know when you catch these – I do appreciate hearing about them. I add corrective changes immediately because it improves the product! Hopefully this isn’t your first experience with a soldering iron. If it is, though, or this is your first solid-state project, here are some tips to ensure your success: The SW-40+ board is double-sided, and all holes on the board are plated-through. This means that you do not need to solder on the top side of the board. Use a small iron in the 25-watt class (such as a Radio Shack #64-2070) and keep the tip clean. Use a moistened sponge or paper towel and clean the tip periodically as you work. TOOLS You’ll need the following tools: Soldering iron – 25-40W, solder Diagonal cutters Needle-nose pliers (helpful) Small slot screwdriver Magnifying glass (recommended) Apply only as much heat as is needed to get a good joint. A small vise to hold the printedcircuit board may make soldering easier. Touch the soldering iron tip to the PC board trace and the component lead simultaneously. Within a second or two, apply solder and you’ll see the solder flow onto the junction. Withdraw the solder and then the soldering iron. TEST EQUIPMENT You’ll need the following: DC power source – 12-14V @ 500mA min. Multimeter Another transceiver (for final adjustment) Frequency counter (helpful but not essential) Avoid the temptation to load solder onto the joint until no more will fit! This is an invitation for trouble, as solder bridges may form across the closer trace separations. Here’s what the correct and incorrect joint treatments look like: First Things First - what you should know You don’t need to be an expert in all phases of this craft, but you should be comfortable with the basics before you embark on this adventure. D .Benson, K1SWL 2/9/2007 2 PLEASE READ THE SECTION BELOW BEFORE REMOVING ANY PARTS FROM THE CIRCUIT BOARD Get yourself a roll of desoldering braid (Radio Shack #642090B). Lay the end of the braid down on the joint to be cleaned and press the soldering iron tip over the braid. Within several seconds you’ll see the braid begin to wick up solder from the joint. Remove the braid and reapply a new section as needed until the joint is clean. It may be necessary to pull the component out from the top side of the board while heating the joint. Leave the iron tip on the board only as long as necessary to do the job – the PC board traces will eventually delaminate (peel off) if overheated. If that still doesn’t do the trick, it may be necessary to cut the offending part off on the top side and pull the remaining leads through with pliers. Contact me for replacement parts if necessary. Winding Toroids: Count as you go. Draw each turn snug against the core to ensure a trim and tight winding. Please ensure that none of the turns is wound “over” (on top of) its neighbors. Double-check the turn count when you’re finished. Use your fingernail or a small screwdriver to “bump” over each turn as you count – this is much easier than counting by eye. Trim the excess wire off to about ¼” and strip the insulation off with a hobby knife. Counting the turns If the wire passes through the toroid center hole, it counts as a turn. If you need to remove a transistor I’d highly recommend sacrificing the part by snipping it off on the top side of the board. The TO-92 pads in particular are small and the leads are best pulled out independently to minimize the risk of lifting pads. After removing a component from the board, the through-hole will probably still be blocked with solder. Use a dissecting needle, dental probe (explorer), or even a large sewing needle, applying heat to the needle and board trace simultaneously until the tool pushes through. D .Benson, K1SWL Small Wonder Labs 2/9/2007 3 Materials You’ll find the following items included with your SW40+ kit: 1 bag of small parts (resistors, caps, etc.) 1 antistatic bag (semiconductors) 1 bag, miscellaneous parts 1 printed circuit board This manual Reference designators: Each component is uniquely identified by a reference designator. Bypass capacitors are identified as C100 and up. “C7”: Capacitor C7 is an assortment of 6 different capacitors designated ‘C7A’ through‘C7F’. Selection and installation of this capacitor is described later in the text. Note: The RF chokes for this kit are supplied in the ‘miscellaneous’ bag’ to keep them separate from similarlooking resistors. (You may want to reproduce the schematic and pictorial pages so you can mark them as you work, and still keep the originals clean.) Special Parts Notes • Monolithic capacitors: The printing on these parts is tiny! I’d highly recommend using a magnifying glass to verify component values before installing them. IF Transformers: Capacitors: Although not illustrated on the schematic drawing for reasons of drawing clarity, T1-T3 contain internal capacitors. Do not remove these capacitors. Here's a general rule for capacitor markings: If 3 digits are printed on the capacitor, the first two are significant figures and the third is a multiplier. Examples: '471' = 47 x 101 = 470 pF '103' = 10 x 103 = 10,000 pF = .01 uF Letter suffixes: J=5%, K=10%, M=20%. RF Chokes: The order of the color-bands on the RF chokes may vary by manufacturer. Parts List - SW-40+ Transceiver Qty 2 1 9 3 2 1 1 1 7 1 1 2 Ref. Desig. Description Identification C3,9 C7A C2,7B,11,17,18,28,30,32,40 C1,7C,16 C7D,8 C7E C7F C7G C12-15,22,23,29 C31 C10 C37,39 10 pF ceramic disk 22 pF NPO cer. Disk 47 pF NPO cer. Disk 68 pF NPO cer. Disk 82 pF NPO cer. Disk 100 pF NPO monolithic cap 120 pF NPO monolithic cap 150 pF NPO monolithic cap 150 pF ceramic disk 220 pF ceramic disk 270 pF ceramic disk 470 pF ceramic disk '10' '22' '47' '68' '82' epoxy, '101J' epoxy, '121J' epoxy, '151J' '151' '221' '271J' '471J' D .Benson, K1SWL Small Wonder Labs 2/9/2007 4 Parts List (continued) 1 1 2 1 1 11 1 7 1 2 1 1 9 1 1 1 1 1 2 1 1 3 1 2 1 1 3 2 2 1 2 4 4 1 3 4 1 4 3 1 1 3 1 5 C25 C38 C4,5 C6 C26 C21,33-35,102-105,108,109,111 C19 C20,24,36,101,107,113,114 C110 C27,106 C112 D1 D2-10 D11 D12 D13 L1 L2 L3,4 Q1 Q3 Q2,4,5 Q6 RFC1,2 RFC3 R24 R6,14,27 R28,29 R1,26 R19 R17,25 R2,3,21,22 R10,16,20,23 R15 R4,7,11 R8,12,13,18 R9 S1-S4 T1-3 T4 U2 U1,3,5 U4 Y1-5 D .Benson, K1SWL 820 pF mylar cap 1000 pF NPO mono. cap 2700 pF NPO mono. cap 3300 pF NPO mono. cap .0022 uF mylar cap .01 uF ceramic disk .033 uF disk or mono. cap 0.1 uF mono. cap 3.3 uF 50V radial elec. cap 47 uF 16V radial elec. cap 220 uF 16V or 25V radial elec. cap MV1662 Varicap diode 1N4148A diode 7.5V 0.5W 5% Zener diode 30V 0.5W 5% Zener diode 1N4001 diode T-50-6, see text, p.10 FT37-43, 6 turns T-37-2, 1.0 uH, 16 turns #26 2N5485 or 2N5486 JFET 2N3906 PNP 2N4401 NPN 2SC2166 22uH RF choke 10uH RF choke 500Ω trim pot 10Ω ¼W 5% resistor 51Ω ¼W 5% resistor 470Ω ¼W 5% resistor 1KΩ ¼W 5% resistor 2.2KΩ ¼W 5% resistor 10KΩ ¼W 5% resistor 22KΩ ¼W 5% resistor 47KΩ ¼W 5% resistor 510KΩ ¼W 5% resistor 1MΩ ¼W 5% resistor 4.7MΩ ¼W 5% resistor 8-pin low-profile IC socket 10.7MHz IF transformer FT37-43, 8 turns :1 turn, see text 78L08 voltage regulator SA602AN, or SA612AN NE5532 4.00MHz or 4.032MHz crystal Small Wonder Labs '821J' epoxy, '102J' epoxy, '272J' epoxy, '332J' '222J' '103M' '333J' epoxy, '104' banded end is negative banded end is negative banded end is negative TO-92, 2 leads, stripes only glass body 1N5236 1N5256 black case 0.50" dia., yellow 0.37" dia., dark grey 0.37" dia., red plastic case (TO-92) plastic case (TO-92) plastic case (TO-92) Power transistor Red-Red-Blk Brn-Blk-Blk Blue plastic, 3 leads Brn-Blk-Blk-Gold Grn-Brn-Blk-Gold Yel-Viol-Brn-Gold Brn-Blk-Red-Gold Red-Red-Red-Gold Brn-Blk-Orange-Gold Red-Red-Orange-Gold Yel-Viol-Orange-Gold Grn-Brn-Yel-Gold Brn-Blk-Grn-Gold Yel-Viol-Grn-Gold '42IF123' 0.37" dia., dark grey plastic case (TO-92) 8-pin IC 8-pin IC HC-49/U holder, 20pF 2/9/2007 5 Theory of operation This transceiver is a single PC-board design measuring 2.8” x 4.0” (7 x 10 cm). It features VFO operation with a 35-40Hz tuning range, as well as QSK (full break-in) operation. Let’s take the 50-cent tour: The receiver’s RF input is applied to U1 through T1 and C1, which provide a bandpass filter tuned to 7.0MHz. T1’s secondary winding provides roughly unity gain into U1 to minimize overload (IMD). U1 provides about 13dB of gain in this configuration, and converts the RF input to the IF frequency of 4.0MHz. The L-network (C11 and RFC1) following the mixer serve to step the mixer output impedance down to the crystal filter’s design value. Note that C12 and RFC1 appear to be ‘transposed’; this reflects the board’s physical layout. The crystal filter itself uses 3 crystals. This works well because of the choice of a low IF frequency. Loss through the filter is less than 2dB, and with the component values as shown, the -6dB bandwidth is about 500Hz. Despite the filter’s low parts count, performance is adequate when combined with the AF section’s selectivity. The unwanted sideband image is down about 50dB at the audio chain’s 800Hz peak response frequency. The filter output is terminated in a 470Ω resistor at the input to U3, the product detector stage. U3 converts the 4.0MHz IF signal to audio and contributes another 13dB of gain. BFO crystal Y4 has been selected to match the IF filter frequency, so there’s no BFO frequency trimming needed. The .033 uF capacitor across pins 4 and 5 of U3 provides the first measure of audio low-pass filtering. The two sections of U4 each provide roughly 30dB of amplification. The first section is configured as a differential amplifier to make use of U3’s differential output and rolls off the audio response above 1.5KHz. Diodes D3 and D4 serve to limit the audio swing during transmitter key-down to reasonable values. Without these diodes, this stage saturates and upsets the operation of the following FET switch section. The AF mute function is the familiar series FET switch popularized by W7EL. Despite its relative simplicity, it’s hard to beat this circuit for click-free audio switching. In the “key-up” condition the FET is zero-biased and acts like a resistance of several hundred ohms. In the “keydown” condition the FET is in cutoff (because the gate is now 7-8 volts below the source) and acts like an open circuit, preventing audio from getting to U4B, the audio final stage. This stage is configured as a bandpass filter D .Benson, K1SWL Small Wonder Labs centered at 800Hz. The high gain of the two NE5532 stages (64dB total) allows a design with no IF amp stage. The audio output level is adequate to drive headphones, but it won’t do the job for loudspeaker applications. The AF output stage internally overcurrent-limits on loud signals to provide a ready-made ear protection function. If you’re interested in saving at least 5 milliamps on receive, U4 may be replaced by an LMC662 (available from Digikey). This suggestion is courtesy of Mitch Lee and Dennis Monticelli, from their excellent article, “Revisiting the 40-40” in the ARRL’s ‘QRP Power’. Use good quality low-impedance headphones for best results. “Walkman” headphones are fine, but remember – you get what you pay for. The 3-dollar bargains are distinctly inferior! QSK: The T-R switch function is provided by C40 and RFC3, which form a series-resonant circuit. Diodes D7D10 limit during key-down and thereby restrict the signal levels presented to the receiver front-end during transmit. The double-diode configuration raises the network’s intercept point with respect to W7EL’s original configuration to improve IMD immunity. The LO uses the Colpitts configuration. The frequencydetermining capacitors are NPO (C0G) monolithic types. These devices are extremely compact and offer good temperature stability. C2 and C3 are a voltage divider providing proper injection to U1. Note: If you want broader frequency coverage, the value of C8 may be increased. The useful upper limit for C8 is about 1000pF, and especially at the larger values, capacitor (and varicap diode D1) thermal stability will become crucial. Use NPO/C0G capacitors if possible, if you tinker with this circuit. The design also uses a varicap tuning diode for tuning coverage. While a smooth ball-bearing tuning cap and vernier reduction drive are the preferred approach, that choice drives the cost and mechanical complexity of a transceiver up considerably. The varicap approach supports quite a compact package! If you’ve just got to have RIT, an outboard circuit that injects an adjustable DC offset into the diode bias network on receive does the trick. The transmitter chain is a pretty standard affair. The maximum output power is about 2-2.5 watts, and there’s a drive control at the emitter follower stage (Q4) to adjust the output level. The diode at the base of Q6 serves to ‘clamp’ the signal to Q6 above ground and thus improves drive to the PA by several dB. I don’t feel that the PA requires a heat sink at the 1.5-2.5W power level and CW duty cycles. If you like, there’s room for a ‘compact’style TO-220 heat sink (Digikey #HS-105 or #HS-106). 2/9/2007 6 [ IMAGE SCANNED FROM ORIGINAL DOCUMENT D. Benson, K1SWL Small Wonder Labs 2/9/2007 7 [ SCANNED FROM ORIGINAL DOCUMENT ] D. Benson, K1SWL Small Wonder Labs 2/9/2007 8 Building instructions All parts installed on the PC board should be fully seated. Do not install the parts in “flying-lead” fashion in the hope that it will improve something-or-other! Minimum lead length is important to a successful RF design. Diode installation: All diodes except D1 are bent for “upright” installation. Installation polarity is as shown below. Be sure to note the orientation of the silk-screened circle on the board and install the diode body over this hole. The cathode (banded) end of the diode is oriented at the top. Stuff only a few parts at a time (3-4 pieces). If you try to add too many parts at once between soldering operations, you may lose track and wind up with missing solder joints! Once you’ve stuffed the parts on the board, bend the protruding leads slightly outward to keep them in place while the board is inverted for soldering. Some of the disk and monolithic capacitors may be supplied with a lead spacing of 0.10” (2.5mm). The “SW-40+” has generally been laid out for a 0.20” (5mm) capacitor spacing. The capacitor leads may be gently spread apart near the component bodies and then bent parallel to ease installation. Recommended Assembly sequence: I’ve specified the sequence below, but there’s nothing critical about the order in which the board is populated. Some parts are best installed in a particular order, as noted within each group’s instructions. Directions for winding toroids are found within each group’s assembly instructions. Resistor installation: All resistors except R4 and R21 are likewise mounted in “hairpin” fashion. As with the diodes, try to match the mounting orientation shown on the drawing. (This usually has nothing to do with critical dimensions – if mounted as shown you’ve got better troubleshooting access to circuit points from the top side of the board.) Orientation of resistor (and other non-polar devices) color bands is non-critical. (The figures which follow are for reference only. See the pictorial drawing on p. 8 for component values.) Installing IC sockets: The “notch” or dot at one end should be oriented as shown in the pictorial drawings. Double-check orientation before soldering. A suggestion: solder down two opposite corners of each socket, and then go back and press a fingertip on the socket from underneath while reheating both connections in turn. You may then solder the remaining pads. This precaution ensures that the socket is well seated on the PC board. Some additional tips: It’s helpful to work from one end or corner of the board to the other. This minimizes the “tight squeeze” cases where the last part in a cluster has to drop into a tight space. D. Benson, K1SWL Small Wonder Labs 2/9/2007 9 (J4) D13 Y4 Y3 Y1 C15 C16 C13 C17 C15 D2 C12 SA R1 612 C105 U3 C104 1N4001 78L08 Y2 C14 [ ] Install D13, U2, C102, and C113. If you have the companion enclosure kit, install connectors J4 (2-pin) and J2 (3-pin) as well. This step supplies DC power to the board and installs the 8 Volt regulator IC. C113 .1 uF (When these components have been installed, the product detector/BFO and crystal filter sections of the transceiver are complete.) [ ] Install an 8-pin IC socket at U1. (J2) Group 1 assembly -reference only- C102 Install the components shown below: U2 L1 (yellow core) is wound using the largerdiameter magnet wire from the “Miscellaneous” envelope. Wind with 25 turns (24 turns for Novice-band operation), prepare lead ends, and install on the board. All other toroids use the smaller-diameter wire. [ ] Install an 8-pin IC socket at U4. [ ] Install the components shown below: R6 R11 C10 R8 D5 R4 C20 C19 C21 C25 R10 C23 D3 C27 R14 J3 R7 D4 NE R2 5532 U4 R3 C22 C107 L1 install as shown here. Silkscreen is wrong. C9 C4 C8 R17 Q2 C6 C5 J1 C7 R9 Q1 C24 C26 C106 C7 is not installed at this time; see “Alignment” for installation procedure. R15 R16 C3 T1C101 C2 R18 C103 D1 RFC1 C11 (When these components have been installed, the audio amplifier section of the transceiver is complete.) C1 U1 [ ] Install an 8-pin IC socket at U3. (When these components have been installed, the receiver portion of the transceiver is complete.) [ ] Install the components shown below: Note: the 5 crystals supplied with this kit have been preselected as a group. They are interchangeable within this group. Do not, however, substitute replacement parts – contact me for assistance. D. Benson, K1SWL Small Wonder Labs 2/9/2007 10 [ ] Install an 8-pin IC socket at U5. [ ] Install the components shown below: The following components are polarity-sensitive: D11, C110, Q3-Q5 Spacing on C31 (between transformers T2 and T3) is quite tight – install this capacitor prior to installing T2 and T3. 5) Trim off the free end of the wire so that it has about ¼” (6mm) more than is needed to reach pad S1. Repeat the lead preparation as in Step 1 above. 6) Install this lead-end in S1 and solder. (When these components have been installed, the transmitter mixer, bandpass filter, and driver sections of the transceiver are complete.) [ ] Install the components shown below: Transformer T4 (grey core) is wound with 4” (10cm) of magnet wire for the primary winding. The primary winding is wound first, using 8 turns. Install T4. [ ] Add a secondary winding to T4 as follows: 1) Strip 1/8” of insulation from one end of the 3” length of insulated wire. Twist the wire gently between your fingertips to ensure that all strands are bundled together. Tin this lead-end with solder. 2) Install this lead-end in S2 and solder. 3) Take the free end of this wire in the direction of S1 and then double it back through the whole in T4. 4) Draw the lead snug (not tight!) and proceed around the toroid material until you’ve formed one complete turn through the toroid as shown below: D. Benson, K1SWL Small Wonder Labs The following components are polarity-sensitive: C112, D6-10, D12, Q6 Q6 (2SC2166) is installed with the metal tab to the rear (or ‘top’ when viewed from directly overhead). When viewing the board from the front edge (U1, U3, and U4 nearest you), Q6’s labeling must be visible. 2/9/2007 11 L2 is wound using 4” (10cm) of wire on an FT37-43 (grey) core. Wind 6 turns on this core, prepare lead ends, and install on the board. L3 and L4 are each wound using 10” (25cm) of wire on a T37-2 (red) core. Wind each with 16 turns, prepare lead ends, and install each of these on the board. (When these components have been installed, the board assembly is complete.) If you have not already done so, install all integrated circuits on the board as indicated on page 8. Be sure that the ICs are oriented properly – the dot or notch is on the left side of the 8-pin DIP ICs as shown on the pictorial. Wiring the SW-40+ The figure below shows the schematic interconnect between the SW-40+ board and the outside world (more on alignment later). Short, direct leads between the SW-40+ board and your connectors and controls are advisable. If you’re going to run the RF output more than a couple of inches to an antenna jack, coax (such as the subminiature RG-174) is recommended. The other interconnect wiring is less critical, but try to avoid routing the wiring over the audio (U4) filter section if possible. CLEAN UP YOUR ACT! Before you install the finished PC board into an enclosure, grab some cotton swabs and use acetone (nail polish remover) to remove solder flux from the foil-side of the PC board. The result is a much cleaner appearance once you’ve completed this step. D. Benson, K1SWL Small Wonder Labs 2/9/2007 12 Wire the connectors and controls to the SW-40+ as shown pictorially below. Note that the keying return line lacks its own distinct board connection. This return line is shared with the headphones’ return. STOP! Before you progress to the next phase of the project, this might be a good time to check out the SW-40+. Add the various connectors and controls using temporary leads before you get the project buttoned up in a box. If you need to do any troubleshooting, you’ll have saved the aggravation of having to undo all the wiring to get at the bottom side of the board! “SW-40+” Mechanical Details The pictorial figure below shows some ideas for connectors and their accompanying mounting-hole diameters. These are merely suggestions and are a matter of personal preference. The board itself is mounted in an enclosure at the board’s four corners using #4 machine screw hardware. #4 spacers should be used to separate the PC board from the enclosure by 3/16” or more. (#4 hex nuts are an acceptable substitute for spacers.) D. Benson, K1SWL Small Wonder Labs Enclosures may be found in a variety of styles. Radio Shack offers several types of metallic enclosures. I’d especially recommend Hosfelt Electronics, Inc., who carry enclosures offered by a number of companies. There’s no minimum order, and they can be reached at (800) 524-6464 for a catalog. Ten-Tec also offers a complete line of enclosures, and they support small orders as well. Call (800) 231-8842 for a free brochure. 2/9/2007 13 Before the “Smoke Test”: Inspect your work to ensure there are no solder bridges or unsoldered joints. Check to see that the ICs are mounted in their proper orientations. Alignment Alignment is easy with this little rig. For test equipment, you’ll need a main-station rig and multimeter or SWR bridge. Here’s how: Transmitter alignment: [ ] Connect a tuning pot to J2. (See page 13 for interconnect pictorial.) Set the tuning pot to full counterclockwise (0V on the pot’s center terminal). [ ] Connect a 50Ω dummy load to ‘RF Out’ and its adjoining ground return pad. [ ] Set trimmer R24 to the half-scale (‘3 o’clock’) position. Do not exceed the half-scale position until T2 and T3 have been peaked to maximum. Yes…you may have to ‘hunt’ for an output power indication!- those two adjustments peaks are fairly narrow. [ ] Using a small slot screwdriver, preset the tuning slugs in T2 and T3 to the middle of their rotation range. (This is non-critical; there’s no need to count turns.) [ ] Add a clip lead to R29 (see figure below) to serve as a short whip antenna. Leave the other end of the clip lead unconnected, and ensure that this free end is well away from other circuitry. [ ] Ground the “Key” (J3-3) input. [ ] Tune in your transmitted signal on your “big rig” receiver. This should be a strong carrier (S9+20 or better). Be sure to hunt for the strongest signal over a range of 7.0 to 7.3MHz to ensure that you find the primary signal instead of a receiver spurious response. Operating frequency adjustment: [ ] Note the frequency from the step above. Remove power and install a value of C7 in accordance with one of the tables below. For 7-7.05 MHz operation: If the frequency was between Install the following value for C7 7000-7030 7030-7060 7060-7090 7090-7120 7120-7140 7140-7160 7160-7180 7180-7210 (none) 22pF 47pF 68pF 82pF 100pF 120pF 150pF For 7.1-7.15 MHz (Novice) operation: If the frequency was between 7100-7130 7130-7160 7160-7190 7190-7220 7220-7240 7240-7260 7260-7280 7280-7310 Install the following value for C7 (none) 22pF 47pF 68pF 82pF 100pF 120pF 150pF The tables above do not show that more capacitance moves the frequency higher. It means that more capacitance compensates for higher frequency. Are we clear on that? (The approximate formula for the value of C7 is as follows:) [C7] (in pF) = ∆f(KHz) / 1.42 where ∆f is the desired frequency shift D. Benson, K1SWL Small Wonder Labs 2/9/2007 14 previous page. (For the test circuit above, this corresponds to a DVM measurement of 24V DC). Increase drive (turn R24 clockwise) only as needed to get to this level. It’s possible to adjust the operating frequency as much as 15-20KHz downward by squeezing L1’s turns more closely together. If in doubt as to which of two values of C7 to use, install the smaller of the two and compress L1’s turns as needed. Connect the RF output to a wattmeter (if you have one). You can also use your SWR meter with a dummy load connected and set in the “Forward” metering position. If you don’t have either of these pieces of equipment, you can ‘haywire’ the test circuit below on a scrap of copperclad board. This peak detector circuit furnishes a DC voltage to your multimeter. “Can I set it for more output power?” Sure! The component values in the PA stage were designed for maximum efficiency at 1.5W out. The SW+ will deliver considerably more, but please be aware of the following: • • The higher the output power, the more heat is being generated by the PA, and this translates into ‘driftier’ performance in the local oscillator. There’s a possibility of instability in the driver (Q4/Q5) stage with R24 set to maximum. IF THE SIDETONE SOUNDS RASPY OR VANISHES ENTIRELY, reduce the R24 setting. Receiver alignment: Adjust T2 and T3 for maximum indicated signal on your receiver’s S-meter. The adjustment will be somewhat interactive, so alternate between the two for maximum output. [ ] Remove the clip lead. Adjust trimmer R24 as needed for 1.5 watts of key-down power into a dummy load or the test circuit shown on the Troubleshooting the SW-40+ The “bugs” you’re most likely to encounter often turn out to be caused by the simplest of problems. If your SW40+ doesn’t play, the following general suggestions may be helpful: “It works better plugged in!” We’ve all heard that expression before, but unfortunately it’s true. Ensure that DC power is getting to the SW-40+. A board with no voltage anywhere probably isn’t getting power. “The headphones are silent!” It’s probably the same as above – an interconnect problem. The 1/8” (3.5mm) jacks in particular are trouble-prone. D. Benson, K1SWL Small Wonder Labs [ ] Connect a matched antenna to “RF Out” and its ground return. Using a small slot screwdriver, peak T1 for maximum signal (or noise). Once this step is complete, background noise should be noticeably higher with an antenna connected than without. Check once more for solder bridges and missing solder joints. Probing a suspect section of the circuitry with a fingertip or insulated tool will sometimes bring a stubborn circuit to life – if so, check again for a bad connection! Of the returns I see, about 85% of problems are caused by cold solder joints, 5% by solder bridges, and 5% due to incorrect resistor installation. That leaves only 5% for all the other problems put together! ‘Nuff said. Ensure that ICs are installed in the correct location and with the right orientation. Likewise, ensure that the transistors and all diodes are installed with the correct orientation. If you don’t turn up anything with the above steps, see the troubleshooting schematic on the last page of this manual. Using a DVM, check the circuit points noted on the 2/9/2007 15 drawing against your SW-40+ to confirm that the DC voltage readings are all in order. Here’s a rule of thumb for the troubleshooting voltages: I’ve supplied the nominal voltage readings, but there’s some unit-to-unit variation. As an overall guideline, a 20% variation is an acceptable tolerance. If you’re making use of this schematic, “something’s broke”, and things don’t generally break just a little; you’re looking for the obvious departures from the published values. The troubleshooting schematic also lists AC voltage readings in case you have access to an oscilloscope or have a high-impedance input RF probe. Readings are given in Volts p-p. The figure below illustrates IC pinout. The “pin 1 at lower left” convention applies to all DualInline-Package (DIP) ICs. (BOTTOM VIEW) (TOP VIEW) 8 5 4 1 5 4 headphones. Also, a signal source such as your main transmitter (on minimum power, please!) should provide a plainly audible signal when you transmit a string of CW characters just above or below the 4.000MHz IF frequency. Do not connect the main station transmitter to the SW40+! Stray leakage is sufficient. Similarly, you should be able to hear the BFO at about 4000KHz on your main station receiver. If not, these steps point to a problem with U3 or its associated BFO components (Y4 and C17-18). Transmitter Be sure a load is connected anytime you’re troubleshooting the transmitter. Verify that the keying switch Q3 supplies 12V DC to the transmit mixer (U5) and buffer/driver (Q4-5) stages when the “Key” input is grounded. Note that the voltage reading at pin 8 of U5 should be 7.1 to 7.9 volts. No voltage during key-down suggests that Q3 is bad or that D11 is installed backward. 8 Touching a screwdriver to Q6’s case (collector) should yield a distinct (key-down) increase in signal received on your ‘big rig’ receiver. If not, suspect Q6. 1 DOT AND/OR NOTCH “Strange but True” – In general, the ICs themselves shouldn’t be prime suspects during the troubleshooting process. Despite their complexity, they’re very reliable, and I’ve had to replace these parts at the rate of only 1 for every thousand or so shipped! If those steps don’t turn up anything, here are some additional steps to try: Receiver Touching either of the 10K resistor leads to the left of the AF Amp IC (U4) should cause an easily-audible hum or buzz in the headphones. If not, and Vr (the 8V supply) is OK, the NE5532 op amp (U4) is suspect. Touching an antenna wire to the 470W resistor to the left of U3 (product detector) should cause shortwave “crud” to be audible in the D. Benson, K1SWL Small Wonder Labs If you want to change the sidetone pitch, increasing the value of C29 raises the sidetone pitch (and Tx offset), and decreasing that cap lowers it. Don’t panic! … and don’t smash your SW-40+ against a wall! If all else fails, contact me for further technical support: Email: dave@smallwonderlabs.com Troubleshooting/alignment is available for a $30 fee ($35 outside the US) . The unit will be returned to you in working condition and will include a troubleshooting report. The price includes return shipping. Please do not send the unit without contacting me first. [ We’ve moved- twice- …. and counting- since the original edition of these instructions were published. The work is done off-site in any case, and unsolicited returns tend to end up ‘aging’ under the workbench. ] 2/9/2007 16 D. Benson, K1SWL Small Wonder Labs 2/9/2007 17
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