NOISE REDUCTION ANTENNA Ramsey Electronics Model No. SM100 Trying to receive distant stations “down in the noise” ?!! Frustrated by continuous powerline noise or adjacent channel interference ? Try our signal “magnet” to pull in those weak stations.
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Ramsey Publication No. MSM100 Price $5.00 KIT ASSEMBLY AND INSTRUCTION MANUAL FOR SIGNAL MAGNET NOISE REDUCTION ACTIVE ANTENNA TABLE OF CONTENTS Introduction ................................... 4 SM100 Circuit Description ............ 5 Parts list ........................................ 6 Parts Layout diagram .................... 8 Schematic diagram ....................... 9 SM100 Assembly instructions ..... 12 Setup and Testing ........................ 19 Troubleshooting ...........................
INTRODUCTION From the earliest days of radio until the present, news, sports, and “talk” radio broadcasts have been transmitted using an (A)mplitude (M)odulated waveform. This type of transmission ensured reliable broadcasts with a large transmission range. In fact, large AM transmitters are used on the shortwave radio bands to send signals around the world! Sounds almost to good to be true? Well, there are a few disadvantages.
electromagnetic waveform is also produced. This waveform is not susceptible to the ravages of electrostatic bursts so it is more desirable to receive. Well, this is exactly the problem we encountered here at Ramsey. While trying to “keep an ear on” the football sports broadcasts 90 miles away, power line noise and low power conditions caused us to string a long wire antenna in hopes of receiving a stronger signal.
SM100 PARTS LIST RESISTORS 1 1 3 5 1 1 2 1 1 1 10 ohm [brown-black-black] (R1) 75 ohm resistor [violet-green-black] (R14) 470 ohm [yellow-violet-brown] (R5, 11, 15) 1K ohm [brown-black-red] (R2, 3, 4, 7, 13) 8.2K ohm [grey-red-red] (R8) 10K ohm [brown-black-orange] (R 9) 100K ohm resistors [brown-black-yellow] (R10, 12) 1 megohm resistor [brown-black-green] (R16) 5K ohm trimmer potentiometer [marked 502M] (R17) 10K ohm PC mount potentiometer (R6) CAPACITORS 5 4 3 2 .
1 1 2 1 1 1 1 1 1 1 9 inch length of RG-174 mini coaxial cable 1/2 inch chassis mount “F” connector, with nut and ground lug 7 inch lengths of 1 inch diameter PVC pipe. 1 inch PVC elbow 1 inch PVC endcap with a .
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SM-100 PARTS FINDER DIAGRAM LONG LEAD SM100 • 9
Now, let's get building! First things first. You'll notice that the two circuit boards are connected together. Before we begin building. we’ll need to separate the circuit boards by gently twisting the smaller SM100A circuit board to separate it from the larger SM100C board. You may use a small file or sandpaper and take off any sharp edges that were created when the PC board “broke”.
6. Install 1N4002 diodes D1 and D2. Notice that the bands do not face in the same direction when installed. 7. Install C1, 220 uf electrolytic capacitor. Electrolytic capacitors are polarized with a (+) and a (-) lead and must be installed in the correct orientation. Ordinarily, only the negative side is marked on the capacitor body with a dark band and the (-) sign clearly shown, while PC boards will usually show the (+) hole location. Use care to ensure proper polarity.
18. Install R4, 1K ohm (brownblack-red). LED (-) 19. Install R1, 10 ohm (brownblack-black). Leave these leads as long as possible PC Board 20. Locate and install Q1, a (+) 2N3904 transistor. Transistors have three "legs" and must be mounted correctly. Notice that the part contains a "flat" side with the writing imprinted on it. Be sure to follow the parts diagram for correct placement.
31. Install Q5, FET marked 2N5485 or MPF102. Make sure that the flat side is facing C13. 32. Install C10, .1 uF capacitor (marked .1 or 104). 33. Install D6, a varactor diode. It looks just like a transistor with only two leads, and is marked MVAM108. A varactor diode acts as a voltage controlled variable capacitor. By increasing or decreasing the DC voltage into the varactor, we can tune the circuit to the desired frequency. 34. Install C8, a 10 uF electrolytic capacitor.
46. Install C12, .01 uF disc capacitor (marked .01 or 103). 47. Install R11, 470 ohm resistor (yellow-violet-brown). 48. Install D7, 12 volt zener diode (grey glass marked 1N759A). A 12 zener diode has no greater than 12 volts across it. This means that there is always 12 volts at the base of Q3 under normal operating conditions. 49. Install C14, .01 uF capacitor (marked .01, 103 or 10nF). 50. Install C9, 10 uF electrolytic capacitor.
Wrap another six turns of foil and cut it. You may wish to hold down the foil with a small piece of tape at each end. 56. Using a sharp hobby knife, cut away a strip of aluminum foil the length of the 1/2 inch PVC about 2/10 of an inch wide. There must be no electrical connection across this gap. By cutting away the aluminum foil, we have retained the foils ability to block electrostatic waves, but not magnetic waves because it is not a full turn. See the diagram on page 17 for a pictorial description.
63. Carefully push the antenna board into the PVC pipe until only the F type connector extends from the end. Fit the PVC pipe onto the elbow. You can now place the caps on both PVC pipes. Be sure that the one that covers the antenna board has a hole just large enough to allow the connector to pass through. 64. Connect a coaxial cable between the main board and the antenna board. The cable should have an RCA type connector on one end, and a type F adaptor on the other.
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TUNING YOUR SM-100 TO OTHER FREQUENCIES VARACTOR TUNING VALUE 70 32 20 10 TURNS TURNS TURNS TURNS 30 pF 1.67 MHz 4.11 MHz 6.5 MHz 13 MHz 350 pF 490 KHz 1.2 MHz 1.9 MHz 3.8 MHz TUNING YOUR SM-100 TO OTHER FREQUENCIES. In order to use your SM-100 on other frequencies, you must wrap the coil differently. Using the table above, and knowing your intended frequency range, pick the correct number of turns for your purposes.
Now you are all set to sit back and enjoy your Signal Magnet! We hope that you find it both useful and valuable, both as an educational tool, which you have already benefited from, and a recreational one, which you will enjoy for years. The SM100 is not intended to replace long wire antennas, although under certain conditions, it will outperform them. Please be aware that you may encounter stations that you will receive better on another antenna. For this reason, we have included a bypass jack.
suspect a construction problem on the main board and inspect it for incorrectly placed parts and bad solder joints. Problem: “The antenna doesn't pick anything up, but signals are received through the existing antenna.” Solution: You probably have an faulty wire connection, or a problem on one of the two boards. Be sure to inspect each part carefully. Using an ohmmeter, make sure that there is a DC entering the antenna board from the main board.
Problem: “Hey, I don’t own an AM radio!” Solution: We can’t help you with that, but the Signal Magnet does work great with our HR40 40 Meter Receiver Kit! SM100 • 21
CONCLUSION We sincerely hope that you have enjoyed the construction and use of this Ramsey Kit. As always, we have tried to compose our manual in the easiest, most “user friendly” format that is possible. As our customers, we value your opinions, comments, and additions that you would like to see in future publications. Please submit comments or ideas to: Ramsey Electronics Inc. Attn. Hobby Kit Department 590 Fishers Station Drive Victor, NY 14564 or techsupport@ramseymail.
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.
SM100 Signal Magnet Quick Reference Page Guide Introduction .................................... 4 SM100 Circuit Description ............. 5 Parts list ......................................... 6 Parts Layout diagram .................... 8 Schematic diagram ........................ 9 SM100 Assembly instructions ..... 12 Setup and Testing ........................19 Troubleshooting ............................20 Ramsey kit warranty .....................
