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Ramsey Electronics manual ASSEMBLY OF THE RRW1A

Models: RRW1A

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ASSEMBLY OF THE RRW1A

Assembly of the RRW1A is straight forward but it does require some time and patience. To get our bearings, we will start by mounting the power jack and move on from there. It serves as a good reference point for the other parts.

‰1. Install J1, the 2.1 mm power jack. Be sure to get a solid connection to all three pads as this will have to take some mechanical strain during normal use. Use ample solder (without ‘globbing’ it on of course).

‰2. Install R6, the 270 ohm resistor (red-violet-brown).

‰3. Install C7, the 2.2 pF ceramic capacitor (marked 2.2). C7 acts as the feedback path for our “Colpitts” style oscillator. This capacitor combined with the next one (C8) and the saw resonator (X1) make this circuit oscillate at the required frequency. Note that this is one of the rare exceptions to installing at 90 degree angles. This part is actually installed at a 45 degree angle to keep lead lengths as sort as possible. This goes to show how important it is to keep your lead lengths short! Even a small amount of trace can introduce inductance that may prevent our oscillator from working properly.

‰4. Install C8, the 8.2 pF ceramic capacitor (marked 8.2).

‰5. Install C3, a 0.001 uF ceramic capacitor (marked .001 or 102 or 1 nF).

‰6. Install L1, a 33 nH 4-turn inductor. Be careful not to distort or crush this when installing it.

‰7. Install Q1, one of the 2SC2498 transistors (marked C2498 or C2570). Pay close attention to the Parts Layout Diagram and the silkscreen on the circuit board for proper orientation (the flat side is a good indicator). Right next to Q1 is Q2 (another 2SC2498 transistor) so make certain to use the correct mounting holes.

‰8. Install Q2, another 2SC2498 transistor (marked C2498 or C2570). Again note the orientation of the flat side before soldering.

Transistor Q2 provides the amplification needed to keep the 433.42 MHz RF oscillator going. Q1 and its surrounding parts form a special buffer stage which isolates the antenna from the oscillator. If it wasn’t for this buffer stage, the oscillator could stop working whenever things like your fingers or a metal object are nearby. This pair working together forms a very stable oscillator which resists a lot of external changes to maintain performance!

‰9. Install X1, the saw resonator (TO-39 metal case). This is the component that determines the operating frequency of the oscillator by interacting with the feedback capacitors surrounding Q2. Note the silkscreen on the circuit board for proper orientation.

RRW1A • 10

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Page 10
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Ramsey Electronics manual ASSEMBLY OF THE RRW1A
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FAQ

What components are needed for the assembly of the RRW1A?

The assembly requires components such as the power jack, resistor, capacitors, inductor, and transistors, among others. Each component plays a crucial role in the functioning of the satellite radio.

How critical is the orientation of the components during assembly?

Proper orientation of the components is essential for the satellite radio's functionality, as incorrect placement can affect the performance of the oscillator and other circuitry. Consult the Parts Layout Diagram and the silkscreen on the circuit board for guidance.

What is the purpose of the saw resonator in the RRW1A?

The saw resonator, housed in a TO-39 metal case, determines the operating frequency of the oscillator. It interacts with the feedback capacitors surrounding the transistors to maintain the stability of the oscillator circuit.