Project 9: 2M CW transmitter

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From: Jeff Herman (jherman@uhunix.uhcc.Hawaii.Edu)
Date: Sun Sep 26 1993 - 22:43:22 EDT


Here's the first of two 2M xmtrs: this one is a 2-transistor CW rig and the
other is a 3-transistor AM circuit which you can FMize yourself (of course
the AM xmtr can be used for CW, too). Here's what Burt Simon in 104 HAM
RADIO PROJECTS FOR NOVICE AND TECHNICIAN (1968) has to say:
   "Here's a dandy 2-meter CW rig that will astound the local gang. Using
only 2 transistors and a 72 MHz third overtone crystal, you can practically
carry the set around with you. It can be built into the tiniest of boxes
and requires only a 9-volt battery to power it. At least one VHFer has
worked 110 miles with this transmitter, and several (built as club projects)
have been equipped with simple one-transistor modulators.
   "Construction is simple, although care must be taken to insure that all
leads are as short as possible. L3 should have its iron-core slug removed.
The RFCs are simple 1/2 watt resistors wound full of #36 enameled wire. To
check their efficiency, use a grid dip meter to see if you're anywhere
near 144 MHz. If they aren't, remove or add turns until the desired frequency
(should correspond with your transmit frequency) is achieved. L1 should be
neutralized by winding a full solenoid of #26 wire on a 1 meg, 1 watt resistor.
Leaving only about 1/2-inch of lead, solder the choke to the crystal socket.
It should resonant at your operating frequency.
   "Main thing is to get the crystal to oscillate. If you have trouble, adjust
L2 and expand or compress the turns of L1 until you hear (using a 2-meter
receiver) the oscillator harmonic. From here on in you can simply tune for
maximum signal using a GDO, field strength meter, or receiver S meter."

Parts List

Q1, 2 2N1745 transistor
C1, 2 .001 mF capacitor
C3, 4 .01 mF
C5 50 pF
C6 12 mF, 5%
R1 510 ohm resistor
R2 30K
R3 10K
R4 100 ohms
B1 9vdc battery
L1 19 turns #24 enameled wire on 1 meg, 1 watt resistor
L2 9 1/2 turns #24 enameled wire on 5/16 inch slug-tuned form
L3 6 1/2 turns #24 enameled wire, spaced 1/6 inch on 5/16 inch slug-
         tuned form
L4 1 3/4 turns #22 enameled wire on cold end of L3
RFC1,2,3 #36 enameled wire wound (and glued) on 1/2 watt resistor. Should
         check to approximately 145 MHz with GDO. If it doesn't, adjust number
         of turns. (Ohmite Z-144)
X1 72 MHz 5th overtone crystal
SW1 SPST switch

            ---L1---
            | |
            | |
------------*--X1--*------------
| |
| |
*------------E-Q1-C------ C1
| B | |
| | ) |
R1 | L2 )------)------C6---*---E-Q2-C------- -----C5---ANT
| | ^ ) | | B | ^ |
| | | )------- | | ) | (
RFC1 | | ) RFC2 | L3) | (L4
| | ) | GND ) | (
| | | | | |
GND -------*--R2-*--* R4 ------* |
        | | | | | | | GND
        | | | | | | |
       C2 R3 C3 | GND C4 RFC3
        | | | | | |
        | | | | GND |
      GND GND GND | |
                        -----------------------------------*---SW1--B1+--GND

Notes: Observe good VHF wiring techniques (we can't be as sloppy here as
we are down on the HF bands!) The positive pole of B1 goes to ground. I
attempted to use arrows to indicate the adjustable coil forms. Nothing
was said about the two taps coming off of L2 - you'll have to experiment
as to their placement. C1 jumps over the other tap from L2.

If any of you build this pup let the rest of us know how you got it to
work.... (who in the world has even got 72 MHz xtals anymore?)

Jeff NH6IL (ex WA6QIJ)


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