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Ramsey Electronics DA25 - page 1
DA25 • 1 BROADBAND DISCONE ANTENNA KIT Ramsey Electronics Model No. DA25 Looking for a broadband antenna with a f ull 360 degree coverage? Discover what comm unication professionals have known for years using a “discone” antenna. Use this antenna to bring a multitude of si gnals out of the nois e making it ideal for scanners and Ultra High th ...
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Ramsey Electronics DA25 - page 2
DA25 • 2 RAMSEY TRAN SMITTER KITS • FM100B Profe ssional FM Stereo Transmitter • FM25B Sy nthesized Ster eo FM Transmitter • MR6 Model Rocket Tracking Transmi tter • TV6 Telev ision Transm itter RAMSEY RECEIVER K ITS • FR1 FM Broadcast Receive r • AR1 Aircraft Band Receiver • SR1 Short wave Receiver • SC1 Short wave C onverter RAM ...
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Ramsey Electronics DA25 - page 3
DA25 • 3 BROADBAND DISCONE ANTENNA KIT DA25 Ramsey Public ation No. MD A25 Price $5.00 TABLE OF CONTENT S Introduction ... .............................. 4 Discon e Ci rcuit d escr ip tion ......... 8 Parts li st ........ .............................. 1 0 Assemb ly instr uction s ................. 11 Installation and Important notes .. 16 Using ...
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Ramsey Electronics DA25 - page 4
DA25 • 4 INTRODUCTION In today’s ever growing “wireless” soci ety, it almost seems a bit ironic that antennas have become less and less the to pic of in terest in ho bbyist circ les. The recent advances in wireless technology have shrunk antennas to ever smaller an u nobtrusive size s. An examp le of this is the cable televis ion indu stry. ...
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Ramsey Electronics DA25 - page 5
DA25 • 5 before we snapped th e rope, the sound waves would arrive much quicker than the “rope wave” would . In the case of r adio waves, the rate at which the waves travel is much faster , reaching the sp eed of light (1 86,000 miles / second, or about 3x10 8 meters / second) in a vacuum. Radio waves do travel slightly slower in a ir however ...
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Ramsey Electronics DA25 - page 6
DA25 • 6 What Are We Driving At? Time to pull some of that theory together and get some answers: Since: λ = v x T And T = 1 / f We can substitu te and g et: λ = v / f Since the velocity equals “c” we wind up with: λ = c / f The wavelength of the radio wave equals the speed of light divided by the frequency. Lets plug some numbers into our ...
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Ramsey Electronics DA25 - page 7
DA25 • 7 one radio frequency (or RF) cycle. Since the cha rge traverses the wire twice, the length of wire needed to permit the charge to travel the total distance in one cycle is λ / 2, or one half the wavelen gth. Therefore, the shortest resonant wire length will be one ha lf wavelength long. Let’s consi der a “half wavelength” e xample ...
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Ramsey Electronics DA25 - page 8
DA25 • 8 What About Impedan ce Matching and VSWR ? Another consideration with electrom agn etic wave antennas is the “match” presente d to either the re ceiver or tran s mitter. In our discussion of wavelength and resonant frequencies it became appare nt that the length of the antenna is critical to match that of the desired frequency. A smal ...
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Ramsey Electronics DA25 - page 9
DA25 • 9 Ramsey of fers two mo dels of this p ar ticular antenna, one with no active components and the other with a low noise preamplifier to further boo st the antenna gain. The DA25 kit which you are about to assemble is the non-preamplified version. The advantages to this parti cular model are its ease of use (no external power required) and ...
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Ramsey Electronics DA25 - page 10
DA25 • 10 PARTS SUPPLIED WITH Y OUR DA25 KIT 1 3 Qt. funnel “cone” 1 7 inch pie-plate ( CAUTION, EDGES MAY BE SHARP! ) 3 #6 – 32 x 1/4” screws 3 #6 – 32 M-F stand-offs 3 #6 – 32 nuts 1 DCA2 circuit board 1 PVC coupling 1 3’ BNC cable RAMSEY "Learn-As-You-Build” KIT ASSEMBLY There are solder con ...
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Ramsey Electronics DA25 - page 11
DA25 • 11 DA25 DISCONE ANTENN A KIT ASSEMBLY Although we know that you are anxious to complete the assembly of your an- tenna kit, it is necessary t o assemble it in a specific order to insure the proper operation of the finished unit. Try to avoid the urge to jump ahead installing components . Since you may appreciate some warm-up soldering pra ...
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Ramsey Electronics DA25 - page 12
DA25 • 12 1. Carefully “tin” the center co nduct or of the cable by adding a small amount of solder to the twisted center conductor. Use care not to leave the soldering iron in contact with the wire for too long as it can melt the center insulation. Tinning allows us ea sier installation of the coaxial cable to the circu it board as sembl ...
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Ramsey Electronics DA25 - page 13
DA25 • 13 Now we are getting somewhere! All your careful preparatio n will pay dividen ds as we install the coax cable to the circui t board. We did this first as it can be quite difficu lt to perform this op eration once the circuit board is installed on t o the cone. 5. Using the 3 #6-32 screws provided, insert th em through the circuit boa ...
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Ramsey Electronics DA25 - page 14
DA25 • 14 6. Install the circuit board assembly to the fu nnel cone as shown. Use care to center the circuit board before yo u solder the assembly completely. It may be easier if you “tack solder” the board into place before you run a ring of solder completely around the board. Careful now, the entire assemb ly will be quite hot while you ...
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Ramsey Electronics DA25 - page 15
DA25 • 15 8. Solder the center conductor wire into place on the disk section of the an- tenna. Trim off any excess lead that is protruding from the d isk. Have a look at the above diagram to help out if necessary. CONGRATULA TIONS ! Your discone antenna is now complete! Have a final look over your work, paying particular attention to the sold ...
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Ramsey Electronics DA25 - page 16
DA25 • 16 INSTALLATION OF THE ANTENNA MOUNT When you are satisfied that your solder connection s are “just right”, we will install the PVC antenna mast coupler included with the kit. The mast mounting is a 1” PVC coupler. We recommend th at you glue the coupling into place with some RTV or contact cement. Be sure to fit the coupler firmly i ...
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Ramsey Electronics DA25 - page 17
DA25 • 17 USING YOUR DA25 DISCONE ANTENNA Now we are ready for the mo ment of tr uth, the running of your discone an- tenna. Were pretty sure by now you have a place se lected to install it, you can use a couple of nylon wire ties and a bit of 1” PVC pipe to fasten it into place. A fairly good “poor mans” test is to search on your scanner o ...
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Ramsey Electronics DA25 - page 18
DA25 • 18 CONCLUSIO N We sincerely hope that you enjoy the use of this R amsey product. As always, we have tried to compose our manual in the ea sie st, 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 t ...
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Ramsey Electronics DA25 - page 19
DA25 • 19 The Ramsey Kit Warra nty Please read carefully BEFORE calling or writing in about your kit. Most problems can be solved wit hout contacting th e factory. Notice that this is not a "fine print" warranty. We want you to understand your rights and ours to o! All Ramsey kits will work if assembled proper ly. The very fact that you ...
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Ramsey Electronics DA25 - page 20
DA25 • 20 Price: $5.00 Ramsey Publication No. MDA25 Assembly and Instruction manual for: RAMS EY MOD EL N O . D A25 RAMSEY ELECTRONICS, INC. 590 Fishers Station Driv e Victor, New York 14 564 Phone (585) 924-4560 Fax (585) 924-45 55 www.ramseyele ctronics.com REQUIRED TOOLS • Soldering Iron Ramsey WLC-100 • Thin Rosin Core Solder Ramsey RTS12 ...
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