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ALL BAND HF, VHF, UHF
ACTIVE ANTENNA
Ramsey Electronics Model No. AA7
Stuck for antenna space? Don’t want to string any more wires?
This ACTIVE ANTENNA KIT gives you roof-top performance on
a desk top!
• Great for perking up scanner reception.
• Dual preamp HF-VHF/UHF front panel switching.
• Circuit based on true active antenna research.
• Performance rivals units costing many times more!
• Front panel RF gain control.
• Uses Dual Gate MOSFET technology for low noise HF am
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PARTIAL LIST OF AVAILABLE KITS RAMSEY TRANSMITTER KITS • FM10, FM25B FM Stereo Transmitters • FM100 Super Pro FM Transmitter • MR6 Model Rocket Tracking Transmitter • AM1, AM25 AM Transmitters RAMSEY RECEIVER KITS • FR1 FM Broadcast Receiver • AR1 Aircraft Band Receiver • SR2 Shortwave Receiver • HFRC 10 MHz WWV Receiver • SC1 Shortwave Converter RAMSEY HOBBY KITS • SG7 Personal Speed Radar • SS70A S
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Ramsey Publication No. MAA7 Manual Price Only: $5.00 KIT ASSEMBLY AND INSTRUCTION MANUAL FOR AA7 ACTIVE ANTENNA KIT TABLE OF CONTENTS Introduction to the AA7 ............................................. 4 Circuit and Device Description .................................. 4 Active Antennas: Circuits With a Purpose ................ 5 Parts List ................................................................... 6
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INTRODUCTION TO THE AA7 We believe that you will discover and agree with us that your new AA7 is the best VALUE in a true receiver antenna. In its simplest form, an “active antenna” is a small antenna going through an RF preamplifier to a receiver. Generally, the actual antenna may be of several different styles: • broad-band (no tuning required) • fixed-tuned (i.e., pre-set for a specific frequency) • variable-tuning (permits peaking or “pre-selecting” a variety of band choices
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The dual-gate MOSFET amplifier circuit (Q1), selected with S1 in the “out” position is designated the HF preamp circuit, due to the exceptionally low noise level of its operation. This is ideal for enhancing weak CW-SSB signals. This amplifier performs the true “active antenna” function of the AA7. The 2SC2498 amplifier circuit (Q2), selected with S1 in the “in” position, is designated the VHF preamp circuit, due to the excellent VHF (very high frequency) and microwave (baked-
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figure of the amplifier circuit which amplifies the signal from the antenna rod before it gets to the receiver's RF input. We mention these things, with no need to get into a lot of engineering detail, just to let you know that "Active Antennas" are a serious topic among contemporary receiver designers, and that we did our homework in bringing you the economical AA7. AA7 ACTIVE ANTENNA KIT PARTS LIST Please verify that the following items are present before starting assembly. CA
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Needle Nose Pliers (RS64-1844) Small Diagonal Cutters (RS64-1845) ADDITIONAL SUGGESTED ITEMS Soldering Iron Holder/Cleaner (RS-64-2078) Holder for PC Board/Parts (RS64-2094) Desoldering Braid (RS-2090) ASSEMBLY INSTRUCTIONS The following assembly steps are given in accord with the LEARN-AS- YOU-BUILD philosophy for Ramsey Kits. To the extent that is reasonably possible, parts are installed in the order of signal flow as depicted on the schematic diagram, with some discus
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AA7 • 8
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AA7 PARTS LAYOUT DIAGRAM AA7 • 9
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• SOLDER ALL wires or pins of the part, whether the 2 wires of a resistor or the 3 or 4 wires of a transistor. • Trim or Nip all excess wires extending beyond each solder connection, taking care that wire trimmings do not become lodged in PC-board solder connections. Soldering the AA7 Printed Circuit Board 1. Install J1, the RF input jack. Notice that it is connected directly to the screw hole for the extendable whip antenna. Solder all 4 points of th
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14. Install R3, 100K [brown-black-yellow]. 15. If you have completed Steps 4 through 14 correctly, you now have the 4 holes for Q1 surrounded by other parts, making it easy to find! Examine Q1, the dual-gate MOSFET. The schematic diagram shows why it has 4 leads. Insert Q1 so that the square tab is pointing directly at JMP2, but... DO NOT solder Q1's 4 leads until you are satisfied that the tab is oriented as explained, and that the 4 wires are in the respective holes without any
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24. BEFORE connecting battery or conducting any tests, PLEASE recheck each of the preceding steps, looking especially for: • quality of solder connections • correct orientation of Q1 and Q2 • correct orientation of the electrolytic C4 • correct battery wire polarity • correct values for resistors and capacitors INITIAL TESTS No adjustments or alignment is required. See the following section about preparing a reliable and convenient cable for the AA7 and your receiver as well a
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rather than only a receiver or scanner, make sure it is not possible to transmit by accidentally pressing a mike button or CW keyer. Transmitted RF into the AA7 is likely to ruin one or both of the transistors. Transistor Placement Information: Both transistors may be ordered from Ramsey Electronics, but they also may be found at a local electronics parts distributor. You may use either "SK" or "ECG" replacements: 3N201 = ECG454 or SK3991 2SC2498 = EC
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Unusual oscillations in receiver: Some portable receivers not enclosed in metal cases may break into oscillation when connected to any RF preamplifier. Try reducing the AA7 gain control and make sure good grounds are on the interconnecting coax cables. Receiver overloading, heterodynes, images: A preamplifier will intensify any problems with selectivity and image rejection due to poor receiver design. ACTIVE ANTENNA COMPARISONS The author of this AA7 instruction manual has co
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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.
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AA7 ACTIVE ANTENNA Quick Reference Page Guide Introduction to the AA7 .....................................4 Circuit and Device Description ..........................4 Active Antennas: Circuits With a Purpose ........5 Schematic Diagram ..........................................6 Parts Layout Diagram .......................................7 Parts List ...........................................................8 Assembly Instructions .......................................9 Using your AA
