30-Meter QRP (CW)
by P. Wyns, ON7WP (Belgium)
This transmitters' intended purpose is for morse-code only in the 30 meter band (10Mhz). It is a low-power QRP type
and needs to be connected to your existing tranceiver. The harmonic rejections on the prototype were measured at
40dB on 20Mhz and 50dB on 30Mhz.
Component Layout.
1-5/16" x 2" (34mm x 52mm)
double-sided.
Parts List
R1 = 100K C1 = 22nF L1,L3 = 820nH BNC connector
R2 = 4K7 C2,C5 = 1nF L2 = 1.8µH Coolrib for Q2
R3 = 12K C3 = 100nF L4 = T-94-2 (Amidon) Morse-key, single pole
R4 = 18 Ohm C4 = 100pF Q1 = BC547 All-metal case
xtal = 10Mhz C6,C7 = 330pF Q2 = 2N2219(A)
Additional Notes
The transmitter is build as a Colpitts Oscillator with a strong 2N2219(A) transistor. HF-output of the oscillator is
100 to 500 mW, depending on the supply voltage of 5 to 20 Volts. The transmit frequency is stabilized with the
10Mhz crystal. A slight detuning is possible by putting a 150pF trimmer capacitor between C2 and the xtal. The
oscillator signal is taken from the collector of Q2 by induction and via a low-feedthrough filter and guided to the
output. This particular filter is called "Chebychev" and uses standard E12 type values. The oscillator is keyed by
Q1, which biases as long as the morse-key is open and the base of Q1 is at ground level. By keying the morse-key Q1
is blocked and allows Q2 to freely oscillate. For best results, use the double sided pcb as shown above. Coil L4
exists of Primary 6 turns and secundary 3 turns of 0.5mm magnet wire on a Amidon T-94-2 donut. Outside diameter is
24 mm and inside diameter is 14mm; the A(l) value is 84µH per 100 turns and permeability of 10. Q2 needs
a coolrib! The whole circuit needs to be mounted in an all-metal/aluminum case. If you're unable to obtain an
all-metal case, then use a roll of self-sticking aluminum tape (available from your hardware store), just make sure
that all individual pieces of aluminum-tape are conducting with each other. Works fine. Don't forget the coolrib
on T2.
Back to Circuits page
Copyright © Tony van Roon