Ramsey Electronics PR20 manuale d’uso

PR20—1 220 MHz LOW NOISE PREAMP KIT • 16 db Gain, 1 db Noise Figure • Runs on 9 to 15 VDC • Hi-Q tuned input to reduce overload • Small size to fit in any rig • The most popular preamp kit in the USA! • Easy 15 m inute as sembly Perk up your reception on 220 MHz with this easy-to-build an d install kit. Works well with any radio - esp[...]

PR20—2 INTRODUCTION T O THE PR20 LOW NOISE PREAMPLIFIER A “preamplifier” gives an initial boost, measured in decibels, to the leve l of a signal before it is further processed by tuned circuits, filters, amplifiers, mixers, detect ors, or other circuit stages. Preamp s may be designed for either RF or audio use and ma y be either tuned or bro[...]

PR20—3 CIRCUIT DESCRIPTION L1 and C2 form a tuned input filter f or the preamp to reject out-of-b and signals. T he 3 db bandwidth of this filter is 6MHz. L1 is adjustable for pe ak performance. The 2SC2498 transistor is a bipolar silicon NPN low noise UHF/VHF amplifier in a T O-92 case suitable for service up to 5 GHz, with maxi mum device dissi[...]

PR20—4 P ARTS SUPPLIED WITH PR20 KIT CAP ACITORS  2 2 or 2.2pF disc capacitor (C1,2)  1 10pF disc cap acit or (C3)  1 100pF disc cap acitor [m arked 100 or 101] (C4)  1 .01uF disc cap acitor [may be marked .01, 103, or 10n F] (C5) RESISTORS  1 470 ohm [yellow-violet-brow n] (R1)  1 100K ohm [brown-black-y ellow] (R2) OTHER COMPO[...]

PR20—5 RAMSEY PR20 PRE-AMP P ARTS LA YOUT NOTE FOR PR-20: Disregard C6 *[...]

PR20—6 PR20 PRE-AMP A SSEMBL Y PROCEDURE Soldering nine pa rts to a PC board is not a big job, but good perfo rmanc e of the PR20 requires attention to keeping all leads as short and neat as possible. The order of p arts installation is not critical for this and othe r small kit s, so the purpose of the following suggested order of assembly is ju[...]

PR20—7  3. Install C4, 100pF (m arked 100 or 101).  4. Install C5, .01uF (marked .01 or 103 or 10nF). Disc capacito r C5 is the byp ass capacitor for the DC volt age supply points on the PC board.  5. Install Q1, 2SC2498. Press Q1 into it s respective loca tion on the PC board, which should be quite o bvious by the placement of the previ[...]

PR20—8 two mechanical point s after making sure that L1 is presse d firmly against the component side of the PC board. PROGRESS SUMMAR Y : The wiring of y our Ramse y PR series preamp PC board is now complete. It will t a ke you less th an a minute to completely re check every single soldering connection as well as for the appropriate part inst a[...]

PR20—9 TESTING A ND A D JUSTMENT With your preamp installed betw een antenna and receiver , the on ly adjustment needed is the obvious one: peaking L1 for ma ximum signal strength. This ma y require more p atience than most of us would think, because the adju stment should be ma de on a weak signal transmitting long enough to permit the adjustmen[...]

PR20—10 PR20 ON-OFF SWITCHING SUGGESTION Depending on your particular application an d intended frequency , yo u may wish to use a DPDT pow er switch w ith one pole c ontrolling volt age and t he other pole connecting the input and output of the PR20 when the DC su pply volt age is in t he “OFF” position. This setup is very practical when you[...]

PR20—11 A 220 MHz “ACTIVE A NTEN N A ” For situations where a simple indoor receiving antenn a is needed, the P R20 preamp will add considerably improved performance to a wh ip antenna adjusted to 1/4 or 5/8 wave. A nd, for a very well engineered true active antenna fo r both HF and VHF at a break-through low price, take a look at our ne w mo[...]

PR20—12 2SC2498 CHAR A CTERISTICS: The 2SC2498 transistor is a bipolar silicon NPN low noise UHF/VHF amplifier in a TO-92 case, suitable for service up to 5GHz, with maximum device dissipation of 600 milliwatt s. Other max imum ratings: Collector -to-Base V oltage: 25 V Collector-to-Emitter V o lt age: 12 V Base-to-Emitter V o ltage: 3 V Maximum [...]

PR20—13 TROUBLESHOOTING GUIDE The only possible causes for malfunction of th e PR20 are faulty or incorrectly inst alled part s. Re-check your work. T ransistor re placement information is provided. Poor performance such as oscillation can be caus ed by bad p arts-mounting (exc essive lead length of resistors or capacito rs). Erratic operation w [...]

PR20—14 THE RAMSEY PR2: THE UL TIM A TE BRO ADBAND PREA M PLIFIER After y ou find out how practical a well-built PR 20 can be for 220MHz op erating, you will b e quite impressed with the “all bands” higher gain (also with very low noise) plus the convenient AC po wer supply , BNC I /O conn ectors and LED ON-OFF indicator of the Ramsey PR2, av[...]

PR20—15 The Ramsey Kit Warra nty Please read carefully BEFORE calling or writ ing in about your kit. M ost problems can be solv ed w i thout contactin g the factory. All Ramsey kits will work if assembled properly. The very fact th at your kit includes this new manual is your assurance that a team of knowledgeable people ha ve field-tested severa[...]

PR20—16 Published by Ramsey Electronics, Inc. Copyright 1994 All rights reserved. Ram sey Electronics, Inc. 590 Fisher s Station Drive Victor, NY 14564 Phone (585 ) 924-4560 Fax (585) 924-4555 www.ramseykits.com Call or write for our full line cat alog! P ART I AL LI S T O F AV AI L AB L E K IT S RAMSEY TRANSMITTER KITS •  FM10 A , FM 25B[...]