PROJECT 2: QRP 20M CW TRANSMITTER

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From: jeffrey@math.hawaii.edu
Date: Thu Jul 22 1993 - 18:37:44 EDT


Hi Gang,
   Here's the second QRP project taken from 101 EASY HAM RADIO PROJECTS,
by Robert Brown and Tom Kneitel; again, since the book is out of print,
I assume there will be no copyright problems...
   This project is a simple 20 meter CW xmtr with output about 100 mw (?).
Here are the authors' comments:
   "If you have always wanted to try low-power on 20 meters, here is an
excellent method for joining the growing ranks of flea-power addicts -
and doing it inexpensively. This circuit is capable of world-wide QSO's,
given the right conditions and assuming QRM is not present.
   "The transmitter uses a pair of GE-1 universal replacement transistors
in a unique circuit configuration a great more sophisticated than you
would normally expect for an under-one-watt rig. Crystal can be a
fundamental 14-mHz type.
   "L1 should be adjusted for sure-fire oscillation every time the
key is depressed. C4 is simply adjusted for maximum output on the FSM."

PARTS LIST:

C!, C2 .02 uF capacitors
C3, C5 .002 uF capacitors
C4 51 pF variable capacitor
L1 38 turns of No. 22 enameled wire on a 1/2 in. diameter
           slug-tuned form
L2 8 turns of No. 22 enameled wire wound over cold end of L1
L3 Coil, 17 turns of Air Dux 616T (or equiv.) tapped 5 1/2
           turns from cold end
L4, L5 2.5 mH rf choke (National R-100 or equiv.)
M1 1.5 volt dry cell
M2 6 volt battery
M3 14 mHz crystal
Q1, Q2 GE-1 transistors
R1 180 ohm resistor
R2 1.1 megohm resistor

As before, rather than trying to `draw' the symbol for each component,
I've just inserted the part number. Oh, note the polarities of the
batteries M1 and M2. GND = ground, ANT = antenna, E = emittor, ANT
C = collector, B = base, KEY = well, this is a CW rig.... |
                                                                   *----
                                                                   | |
--------*-------- ------------- ----*-----C5--------L3 |
| | | | | | | | C4
L4 M3 E-Q1-C | GND-E-Q2-C | | |
| | | | | | GND GND
| | B | B L5
* --- GND | | | |
| | | | | |
| | | ---------------------- |
R2 | | | | |
| R1 L1 L2 | |
GND | | | *---------------*
    | | | | |
    | GND GND | |
    | *----C2--- C3
    | | | |
    | | | |
    ---KEY--*--+M1--GND ----M2+--* GND
            | |
            | |
            C1 GND
            |
            |
           GND

Note that the collector of Q1 `jumps' over the hot end of L2; this is
the only jump. * = a junction of 3 or more leads.

.... .- ...- . ..-. ..- -. !

Jeff, NH6IL

Jeffrey Herman, University of Hawaii Mathematics, jherman@Hawaii.Edu


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