Ramsey Electronics QRP20 manual Building the VXO Variable Crystal Oscillator

Page 14

‰18. Install R14, 10K ohms [brown-black-orange].

‰19. Install Q4, be sure to orient its flat side correctly as shown.

‰20.Install C15, .01 uf (marked .01 or 103 or 10 nf).

So far, here's what we've accomplished. First, we've got over a third of all the parts soldered onto the board, which should make you happy, and you should be used to locating the correct component holes with increasing ease by seeing them in relation to previously installed components. Secondly, the keying circuit is completed and would be usable, if there was something to key.

From here, we could proceed one of two ways. It would be quite easy to start filling in the holes around the antenna jack, and the project could be done in perhaps another hour. We'd like to suggest a better approach, which is to build up the VXO stage (variable-crystal-oscillator) around Q1 and test it before finishing the rest of the transmitter.

BUILDING THE VXO (VARIABLE CRYSTAL OSCILLATOR):

Your QRP transmitter comes complete with one crystal in the CW range, usually the suggested QRP international calling frequency. S1 permits your choice of any two installed crystals, the one that comes with your kit and another which you may add on your own. If you plan to add a socket for your own crystal, it should be wired to the "A" crystal position.

The PC board used in your kit is common to all the QRP transmitters in the Ramsey Kit line. This means that there are some component locations on the PC board that may not be used on your kit. Please be aware of this and install your parts carefully. The parts layout diagram is quite clear regarding this. (The reason for these holes is that different frequency bands require various styles of inductors and capacitors for correct VXO frequency and shift).

Now, since we have gone to all this explaining, let's install some more parts!

‰21. Install L1, 2.2 uh inductor (green body with two red bands).

‰22. Install C1, .01 uf (marked .01 or 103 or 10 nf).

‰23. Install R2, 1 megohm (brown-black-green).

‰24. Install Varactor diode D3, observe correct placement of the flat side. (Varactor diodes act as a variable capacitor whose capacity is varied by the voltage applied across it).

‰25. Install varactor diode D4, observe flat side placement.

‰26. Install R3, 1 megohm (brown-black-green).

‰27. Install R4, 10K (brown-black-orange).

‰28. Install C2, 68 pf.

QRP-20 • 14

Image 14
Contents CW Transmitter Ramsey Transmitter Kits QRP20 20 Meter CW Transmitter KIT Introduction Watts vs 1 Watt Understanding the Difference QRP-20 WHO should USE a QRP TRANSMITTER? Circuit DescriptionBlock Diagram Parts Supplied with QRP20 Transmitter KIT CapacitorsQRP-20 QRP20 Parts Layout Diagram LEARN-AS-YOU-BUILD Transmitter Assembly Strategy First Assembly StepsQRP-20 Building the VXO Variable Crystal Oscillator Halftime Suggestion Buffer and RF Amplifier Wiring Crystal Oscillator TestingFurther Assembly Your Power Supply and RF Output Power Initial TestsVerifying Transmitter RF Output Maximizing RF Power Output TRANS-RECEIVE OperationRamsey Electronics CASE, Knob & Hardware Option Other Enclosure RecommendationsTroubleshooting Guide Final ConsiderationsQRP-20 Ramsey Kit Warranty Ramsey Model NO. QRP20 Meter CW Transmitter KIT