LOW BANDER Low Frequency SWL Converter Ramsey Electronics Model No. VLF1 Tune in on all that low frequency action your rig has been missing! Get down below 400KHz with an effective and easy-tobuild design. · · · · · · · · · Converts 400KHz shortwave up to 4MHz. Less than 10dB loss from 10KHz to 600KHz! Powered by any 9 - 12 VDC source. Uses analog and digital circuitry in a simple, robust design. E - Z hookup with built in "feed thru" antenna connections - no need to disconnect when not in use! Uses stable crystal oscillator for drift-free operation! Can use 4MHz-10MHz crystal, 4MHz included. Complete and informative instructions guide you to a kit that works the first time, every time. Gain valuable experience by winding a three-coil transformer. VLF1 · 1 PARTIAL LIST OF AVAILABLE KITS: RAMSEY TRANSMITTER KITS · FM10A, FM25B FM Stereo Transmitters · AM1, AM25 Transmitter RAMSEY RECEIVER KITS · FR1 FM Broadcast Receiver · AR1 Aircraft Band Receiver · SR2 Shortwave Receiver · AA7 Active Antenna · SC1 Shortwave Converter RAMSEY HOBBY KITS · SG7 Personal Speed Radar · SS70A Speech Scrambler/Descrambler · TT1 Telephone Recorder · SP1 Speakerphone · MD3 Microwave Motion Detector · PH14 Peak hold Meter · TFM3 Tri-Field Meter RAMSEY AMATEUR RADIO KITS · HR Series HF All Mode Receivers · QRP Series HF CW Transmitters · CW7 CW Keyer · DDF1 Doppler Direction Finder · QRP Power Amplifiers RAMSEY MINI-KITS Many other kits are available for hobby, school, scouts and just plain FUN. New kits are always under development. Write or call for our free Ramsey catalog. VLF1 LOW FREQUENCY SWL CONVERTER INSTRUCTION MANUAL Ramsey Electronics publication No. MVLF1 Rev. 1.1 November 2002 COPYRIGHT 2002 by Ramsey Electronics, Inc. 590 Fishers Station Drive, Victor, New York 14564. All rights reserved. No portion of this publication may be copied or duplicated without the written permission of Ramsey Electronics, Inc. Printed in the United States of America. VLF1 · 2 Ramsey Publication No. VLF1 Manual Price Only $5.00 KIT ASSEMBLY AND INSTRUCTION MANUAL FOR Low Bander, Low Frequency SWL Converter Kit TABLE OF CONTENTS Introduction to the VLF1 ........................ 4 VLF1 Circuit Description ........................ 4 Kit Building Tips ......................................5 Parts List................................................ 7 Parts Layout Diagram ............................ 9 Assembly Instructions...........................10 Setup and Testing ...............................16 Troubleshooting Guide .........................16 Schematic Diagram ..............................17 Ramsey Kit Warranty............................18 RAMSEY ELECTRONICS, INC. 590 Fishers Station Drive Victor, New York 14564 Phone (585) 924-4560 Fax (585) 924-4555 www.ramseykits.com VLF1 · 3 INTRODUCTION You have a great setup, tuning in just about everything in the spectrum. You go up and down, down, down, until...DOH! Your receiver bottoms out. Ever wonder what was down there just under your rig's lower limit? You need a very easy to build and easy to set up frequency converter, so you can delve in to all the wonders that reside in The Low Frequencies. Well, there's some cool stuff down there and that's what the VLF1 is all about: a kit that Ramsey Electronics is only too happy to provide for you. You'll notice that the PC board included with your kit is single sided. It is easy to assemble and a quick look at the parts list reveals 2 ICs and a handful of resistors and caps. This kit uses both digital and analog circuitry to step up a low frequency RF signal to a 4MHz minimum. VLF1 CIRCUIT DESCRIPTION Before we begin dissecting the circuit, let's have a look at the "big picture" and see what it is that we're trying to accomplish. Without getting too much into detailed theory, we need to "mix" the incoming low frequency signal with a high frequency one to produce an output that your receiver can use. As shown in the diagram below: the low frequency input RF signal is added to a high frequency (4MHz) clock producing a high frequency signal. + = VLF1 · 4 Take a quick look at the schematic. The low frequency signal from your antenna is fed into J1. It passes through a low-pass filter made up of L1, L2, L3,C1,C2,C3, and C4. The signal then passes through transformer T1 which produces 2 identical copies of the original signal, with one being inverted. Next is the magic step that creates the high frequency signal for your receiver. The 4053 analog switch alternately switches between the input signal and its inverted version at a frequency of 4MHz. This 4MHz comes from the crystal oscillator made up of the 7404 and its support components. The result of this switching is to produce a 4MHz version of your input signal! That's it, after being amplified by Q1; this signal comes out of J2 and on to your receiver. RAMSEY Learn-As-You-Build KIT ASSEMBLY There are numerous solder connections on the VLF1 printed circuit board. Therefore, PLEASE take us seriously when we say that good soldering is essential to the proper operation of your transmitter! · · · · Use a 25-watt soldering pencil with a clean, sharp tip. Use only rosin-core solder intended for electronics use. Use bright lighting, a magnifying lamp or bench-style magnifier may be helpful. Do your work in stages, taking breaks to check your work. Carefully brush away wire cuttings so they don't lodge between solder connections. We have a two-fold "strategy" for the order of the following kit assembly steps. First, we install parts in physical relationship to each other, so there's minimal chance of inserting wires into wrong holes. Second, whenever possible, we install in an order that fits our "Learn-As-You Build" Kit building philosophy. This entails describing the circuit that you are building instead of just blindly installing components. We hope that this will not only make assembly of our kits easier, but help you to understand the circuit you're constructing. For each part, our word "Install" always means these steps: 1. Pick the correct part value to start with. 2. Insert it into the correct PC board location. 3. Orient it correctly, follow the PC board drawing and the written directions for all parts - especially when there's a right way and a wrong way to solder it in. (Diode bands, electrolytic VLF1 · 5 capacitor polarity, transistor shapes, dotted or notched ends of IC's, and so forth.) 4. Solder all connections unless directed otherwise. Use enough heat and solder flow for clean, shiny, completed connections. SINGLE SIDED COMPONENT SOLDERING INSTRUCTIONS: You'll notice that the circuit board contains plating on only one side of the board. This makes soldering relatively easy for even the inexperienced kit builder. Just take your time and be sure to apply enough heat to the connections. Don't be too afraid of overheating a component, most are fairly hardy and a weak connection will prevent your kit from working properly. In all RF kits it is a good idea to keep the components as close to the board as you can and trim off the excess lengths of the component legs. However, in this kit the highest frequency on the board is around 4MHz, so this isn't as critical as it would be in a higher frequency circuit. VLF1 · 6 VLF1 PARTS LIST Sort and "check off" the components in the boxes provided. We do our best to pack all our kits correctly but it is possible that a boo-boo has occurred and we missed a part. Please note that physical descriptions of parts are for those currently being shipped. Sometimes the parts in your kit may have a different appearance but still have the same values. 3 2 2 1 1 1 10K ohm resistor [brown-black-orange] (R1,R2,R3) 1K ohm resistor [brown-black-red] (R6,R10) 270 ohm resistor [red-violet-brown] (R5,R9) 18 ohm resistor [brown-gray-black] (R8) 1M ohm resistor [brown-black-green] (R4) 3.3K ohm resistor [orange-orange-red] (R7) CAPACITORS 5 .1 uF ceramic disc capacitors [little green, marked 104] (C6, C7, C11, C12, C14) 2 .015 .uF polyester film [brown, marked 153] (C2, C3) 2 .0082 uF Mylar or ceramic disk capacitors [steely blue rectangles, or marked 822] (C1, C4) 1 40 pf adjustable cap [little cube with phillips indent on top] (C10) 2 22 pf ceramic disc [marked 22] (C8, C9) 2 10 uF electrolytic (C5, C16) 1 1 uF electrolytic (C13) 1 1000 uF electrolytic [big whopper cap] (C15) INDUCTORS Note: Inductor color codes can be hard to read. If you don't have an LCR meter, get a bright light and a magnifying glass. You can also check with an ohmmeter to make sure that what you think is an inductor is not a resistor in disguise. The inductors in this kit have almost zero resistance. 2 1 1 22 uH [look like turquoise or tan resistors, red-red-black] (L1, L3) 100 uH [brown-black-brown] (L4) 27 uH [red-purple-black] (L2) SEMICONDUCTORS Note: Chips may have different numbers and letters on them; the important thing is that the numbers listed in brackets are there 1 1 1 1 MC74HC04AN [7404] Hex Inverter (U2) CD74HC4053E [4053] CMOS analog Multiplexer/Demultiplexer (U1) 2N3904 NPN bipolar transistor (Q1) 7805 5 volt regulator (VR1) VLF1 · 7 1 Red LED (D2) 1 4004 silicon diode (D1) Miscellaneous 1 3 1 1 1 1 1 Pushbutton Switch (S1) RCA Jacks (J1, J2, J3) Power Jack (J4) 4MHz quartz crystal (X1) 36 AWG wire for T1 Plastic tuning screwdriver Ferrite core for T1 Now, let's get building! Since you may appreciate some "warm-up" soldering practice as well as a chance to put some "landmarks" on the PC board we'll first install some "hardware" components. This will also help us to get acquainted with the updown, left-right orientation of the circuit board. VLF1 · 8 VLF1 PARTS LAYOUT DIAGRAM VLF1 · 9 ASSEMBLY INSTRUCTIONS Once you've begun to install some of the longer leaded parts, save a couple of clipped off leads to use as jumpers in construction of your VLF1 kit. 1. Install jacks J1, J2, and J3, the antenna input and RF output Jacks. They are RCA PC mount type. These connectors will "snap" into place before soldering. Don't be afraid to completely solder all three ground connections as these will also limit the "stress" on the input and antenna connections. Solder all four "tabs" on the bottom. Be sure to use enough heat to properly "flow" the connection. 2. In the same manner, install power jack J4. 3. Install pushbutton switch S1. Orient the switch so that the end of the switch extends over the edge of the PC board. Be sure to push the switch flush to the circuit board. Solder all six pins. That wasn't so bad, now was it! Recheck your connections for a shiny, smooth solder fillet connecting the component to the PC trace. Touch up any poor looking connections. We'll continue now by building the low-pass filter. The next few parts will make up the low-pass filter at the antenna input of the VLF1. 5. Install C1, .0082µF capacitor (marked 822), by the RCA jacks. 6. Install L1, 22uH inductor (red-red-black. One of the smaller blue green or light tan parts that looks like a resistor). You can check with an ohmmeter to make sure it isn't a resistor. The inductors have nearly zero resistance. 7. Install C2 .015uF capacitor (little brown chicklet marked 153), next to L1. 8. Install C3, the other .015uF capacitor kitty corner to C2. 9. Install L2, 27uH inductor (red-purple-black). 10. Install L3, the other 22uh inductor, kitty corner to L3. 11. Install C4, the other .0082uF capacitor. You have now completed the low-pass filter! It is now time to wire up T1, the three winding transformer. Don't be alarmed, it isn't that hard. Don't be afraid to be a bit sloppy with the wire. The ferrite core is almost an ideal material for wire stripping and if you tug on the wire and it scrapes against the core, the insulation will come off. This will cause a short and you will have to rewind the transformer. The wire must be delicately threaded through the holes in the core. VLF1 · 10 12. Take the 36 AWG wire and cut it into 3, 20" pieces. Now, take 2 of these pieces and twist the ends together about a half an inch. Slip one end of the wire through one hole of the ferrite core, and the other end through the other hole. It should now look like the figure below. 13. Next, take one of the wires and wind it up through the opposite hole and then down through the first hole as shown in the picture. Finally, route it back through the second hole again. 14. Repeat this 12 times. Remember to be delicate and loose with your wiring. Snug the coils as much as you can without having to use anything but gentle force on the wires. 15. Now wind the second wire through the other hole in the same way. Your transformer should now look like this: VLF1 · 11 16. The twisted part is the center tap of the secondary and the other two ends make up the end points of the secondary. You now need to wind the primary. This will go much faster than the secondary winding. Take the third piece of wire you cut and feed it ...