Circuit Description - Ramsey Electronics QRP20 User Manual

On the other hand, if you hear a 1000 watt station producing a moderate signal
such as S4 or S5, you can reasonably assume that you will not have a lot of
luck over that path right now with the theoretical S1 signal level of your QRP
transmitter.
While these figures also can be used to show how nice it is to have a power
amplifier and beam antenna, they indeed serve to show that reasonable signal
levels indeed are achievable with low power and a dipole antenna.
"QRP" enthusiasts have their own rituals, jargon, strategies, QRP operating
contests, magazine columns and books, and convention get-togethers. They
constitute a vital segment of the amateur radio community, because they
consistently demonstrate the feasibility of low-power communication. In fact,
the most avid QRP enthusiasts would not regard communication with a
Ramsey transmitter especially challenging, since they prefer the new world of
milliwatt operation, known as "QRPp"! And, yes, the ones who have conquered
the "milliwatt" world ARE setting records with "milliwatt" tests. With the world
record set in 1970 between Alaska and Oregon on ONE microwatt, think about
it this way: your Ramsey QRP transmitter is almost one million times more
powerful than the transmitter used in that historic test!
WHO SHOULD USE A "QRP" TRANSMITTER?
There is a philosophy that "Novices" should not get started with a very low
power transmitter. The reasoning is that most newly-licensed amateurs need to
build up the confidence that comes with actually making contacts and that they
do not need the additional challenge and pressure of low-power operation.
There is some wisdom in this view, but that opinion should not make
newcomers apprehensive about trying a Ramsey QRP transmitter, IF:
1. This is where your budget is.
2. You can count on somebody to help you with assembly.
3. You can count on somebody to listen to your signal during initial tests.
4. You have a reasonably good receiver.
5. You have space for a normal, no-compromise antenna for the band you
wish to operate, either a standard dipole, or the "inverted V" dipole, or
quarter-wave vertical.

CIRCUIT DESCRIPTION:

In brief, Q1 is a crystal oscillator, amplified by buffer stage Q2, which drives Q3
as the RF output amplifier. Q4 is a PNP keying circuit which opens and closes
the 12VDC supply line to Q1 and the T-R circuitry of D1 and D2.
S1 selects either of two crystals. R1,D3,D4 and L1 form a varactor controlled
series resonant circuit with the crystal. Adjusting R1 permits a crystal frequency
swing of up to 7 KHz, about the crystal frequency.
QRP-20 • 7