Ramsey Electronics QAMP20 manual

QAMP20 • 1 Ramsey Electronics Model No. QAMP20 Need a little extra boost for your QRP rig? Believe it or not, 20 watts is only about an ‘S’ unit below a 100 watt ri g! This nifty little amp will add some “punch” to any QRP transmitter. • Works great with Ramsey QRP rig s or any other 1-2 watt transmitters • Built-in T/R relay automati[...]

QAMP20 • 2 RA M SEY TRA NSMIT TER KIT S • FM10 A, FM25B FM Stereo Transmitters • TV6 Tele vision Transmitter • Cube TV Transmitte rs RAMSE Y RECEI VER KI TS • FR1 FM Broa dcast Receiver • AR1 A ircraft Band Receiver • SR2 Shortwa v e Receiver • A A7 Ac t i ve An t e n n a • SC1 Shortwav e Converter RAMSE Y HOBB Y KITS • SG7 Pers[...]

QAMP20 • 3 Ramsey Publication No. MQAMP20 Price $5.00 TABLE OF CONTENTS Introduction to the QAMP20 ........... 4 How it works .................. ................. 4 Parts list ................. ................. ....... 5 Learn as you Build .................. ....... 6 QAMP20 assembly instructions ..... 7 Initial tests ..... ........ ............[...]

QAMP20 • 4 INTR ODU C TION The Ram sey QAMP serie s of QR P power amplif iers are co mpact 10 to 20 watt RF amplifiers for QRP CW transmitters. These amplifiers are made to be driven by transmitters in the ½ to 2 watt range. Built-in to the power amplifier is a sensitive T-R relay which w ill switch the unit in and out of the antenna line. W hen[...]

QAMP20 • 5 PARTS LIST FOR THE Q AMP20 QR P POWER AMPLIFIER CAPACIT ORS:  1 100 to 220 µf electroly tic capacitor [C1]  1 10 µf electrolytic capacitor [C2]  4 .1 µf disc cap acitors (marke d .1 or 104) [C3,8,10,1 3]  2 180 ρ f disc capacitors (marke d 180 or 181) [C4,7]  2 330 ρ f disc capacitors (marked 330 or 331) [C5,6]  [...]

QAMP20 • 6 REQUIRED, NOT SUPPLIE D:  Ra msey case, knob and panel set, Ramsey part no. CQRP  Matching input and output cables to existing QRP transmitter  12 volt DC pow er supply 3 amp rating  Prop er dummy load or resonant antenna "THE RAMSEY LEARN-AS-YOU-BUILD ASSEMBLY STRATEGY" Take a look at the parts la y out diagra m.[...]

QAMP20 • 7 In all the follow ing instruction steps, our word "INSTALL" means to do the following: • Insert the part, oriented correctly , into its correct holes in the PC board. • If helpful, gently bend the part’s wire leads or tabs to hold it in place, w ith the body of th e part snugl y against the top side (com ponent side) of[...]

QAMP20 • 8  15. Install Q3 and Q4, 2N3904 NPN transistors, observing pro per orientation of the flat side. The se two transistors amplify the signal diode' s output to a level high enough to close relay K1.  16. Install diode D4, 1N40 02 style blac k epoxy diode. Check positioning of th e banded end.  17. Install jumper JMP2. Use a [...]

QAMP20 • 9 These las t four p arts (R8,9 an d C11,12) form par asitic suppr ession net works across each transistor to suppress any te ndency for high frequency oscillation in the power amplifier.  32. Install C3, another .1 µf disc c apacitor (marked .1 or 104 ). Both of these capacitors by p ass the cent er tap of the ferrite transformers t[...]

QAMP20 • 10  41. Winding L1 and L3 toroid RF coils (two identical units ): Locate 2 of the donut shaped yellow toroid cores provided in the kit. Cut 8" of the enam eled magn et wire and, following the dr awing, thread the wire through the core 12 ti mes - not 11, not 13; it MUST be 12 tim es through the core , p ulling each turn gentl y t[...]

QAMP20 • 11 through the core , continuing on in the same direction as before. Tin each end with solder all the way up to the core body. This windin g is the 2 turn center-tapped secondary of T2.  45. Winding T1: Locate the remaining larger 2-hole ferrite core. Cut off a 10 inch length of the enameled magnet w ire and thread the wire through th[...]

QAMP20 • 12  50. Inst all L2, the 14 turn toro id inductor - you ma rked it special, rem ember?  51. Install L3, the remaining 12 turn toroid inductor. This completes the assembly of your QRP power amplifier. Now's a good time to give your masterpiece a good going over, b eing especially alert for any: • bridged-over solder joints; ?[...]

QAMP20 • 13 4. Temporarily install a ju mper from the collector of Q3 to ground. 5. Apply power to the amplifier but do not turn on the transmitter. Measure the current draw n by the amplifier and slowly rotate the bias pot, R4, clock w ise until you reach a reading of ¼ amp. Do n ot allow the curr ent to rise above ½ amp. If you cannot adjust [...]

QAMP20 • 14 Ideally, yo u have a small RF wattmeter, already inserted in the antenna line, capable of accurately measuring low outp ut power in wa tts. And it cost you less than what you paid for the transmitter kit. Right? In the words of Wayne from "Wayne's World" ... Not ! So here are a few other ideas for you to try. Saying the[...]

QAMP20 • 15 KB4ZGC on how to make a highly accurate yet inexpensive dummy load and wattmeter capable of showing 1/10 -watt differences in RF power. If you use a wattmeter characterized for the HF frequency region, it will not give accurate results at the much higher t wo meter fr equencies, although it will be quite adequate for go/no-go testing.[...]

QAMP20 • 16 If you hear an AC hum on the transmitted signal, usual causes are RF getting back into the powe r supply or a bad VSWR on the antenna. These short checks in no way detail any and all problems that can rear their ugly head , but should get you on the way to solving most errors. W e'd li k e to be able to foresee a problem a builde[...]

QAMP20 • 17 While we believe that the Ramsey enclosure and knob option is a fine value for finishing off your Ramsey kit, we are happy to give you a couple of additional suggestions and our reasons for them. If y our first goal is economy and rugged portability, you will find that the circ uit board can be m ounted nicely in a standard VHS videot[...]

QAMP20 • 18[...]

QAMP20 • 19 The Ramsey Kit Warra nty Please read carefully BEFORE calling or writing in about your kit. Most problems can be solve d without contacting the factory . Notice that thi s is not a " fine prin t" warranty . We want you to u nderstan d your righ ts and o urs too ! All Ramsey kits w ill work if assemble d properly . The ve ry [...]

QAMP20 • 20 Q AMP20 20 WATT LINEAR AMPLIFIER Quick Reference Page Guide How it works ................. ................. . 4 Parts list ........... ................ ............... 5 Learn as you Build ........ ................. . 6 QAMP20 assembly instructions ..... 7 Initial testing ..... .................. ......... 12 Verifying RF output powe[...]