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.
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
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 ............
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.
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.
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.
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.
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.
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.
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.
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 down through the left hole leaving about 1/2” sticking out. 17. Now run this wire through the right hole, down through the left, and back up through the right again. This is just like you did for the secondary. 18. Wind the wire 12 more times.
19. Lastly, solder in your transformer, aligning the primary and secondary leads as they appear in the board outline. You have to tin the leads with your soldering iron before you insert them. Get a little solder on your iron and “paint” it on the leads as you heat them. The insulation will melt off and the solder should stick. You will be able to see that the leads are shiny and the red insulation is melted off.
31. Install Q1 the 2N3904 NPN transistor next to C13. This provides amplification for the mixed signal fed to the output jack. Be sure to align the part with the outline on the board. The flat side should face the RCA jacks at the bottom of the board. 32. Install R9, 270 ohm resistor (red-violet-brown) next to C3. 33. Install R8, 18 ohm resistor (brown-gray-black) next to Q1.
47. Install the 7805 voltage regulator, bending the pins back and letting it lay flat on the board as shown in the picture. 48. Install R10, 1K ohm resistor (brown-black-red). 49. Install D2, the red LED, next to the 7805. Observe which way it goes in. The flat side of the LED should match the flat side on the board outline. Leave the leads on the LED long; aproximately 1/2 inch of lead length from the top of the PC board will give you enough space to bend it over and fit it through the case.
SETUP AND TESTING With all this done, it is now time to set up your VLF1 and apply power! The first thing to do is plug in the power adapter and see that nothing burns out or gets hot. If nothing does, congratulations! At least you haven’t made any catastrophic mistakes. The next step is to tune the quartz oscillator to exactly 4MHz. To do this, connect your receiver’s input jack to the VLF1’s output jack J2. Tune your receiver to 4MHz and set it to sideband mode.
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The Ramsey Kit Warranty Please read carefully BEFORE calling or writing in about your kit. Most problems can be solved without contacting the factory. Notice that this is not a "fine print" warranty. We want you to understand your rights and ours too! All Ramsey kits will work if assembled properly. The very fact that your kit includes this new manual is your assurance that a team of knowledgeable people have field-tested several "copies" of this kit straight from the Ramsey Inventory.
VLF1 LOW FREQUENCY SWL CONVERTER Quick Reference Page Guide Introduction to the VLF1 ........................ 4 VLF1 Circuit Description ........................ 4 Parts List................................................ 7 Parts Layout Diagram ............................ 9 Assembly Instructions...........................10 Schematic Diagram ..............................17 Ramsey Kit Warranty............................
