Ramsey Electronics HR30 Instruction Manual - page 12
HR30
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12
capacitor is a first step in setting up the resonant frequency of the SA602’s
internal oscillator, using the resonant LC circuit to be created along with
C1, C3 and L1.
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12. Install C1, 75pF disc capacitor (marked 75 or 75K).
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13. Install C3, .001µF ceramic disc capacitor (marked 102 or .001 or
10nF).
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14. Before installing L2 (marked 42IF-123), examine the inductor. Look at
the bottom side and you'll see a small silver and brown tubular part nested
within the black plastic base. Removing the tubular capacitor is not as hard
as you might expect; just crush it completely with a small screwdriver or a
knife.
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15. Install L2, shielded ocil.
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16. Install C4, 47pF. C4 adds variable capacitance of the varactor tuning
network to the oscillator circuit already formed by L2, C1, C2 and the
SA602.
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17. Install D1, the 1N4002 diode, making sure that the cathode or banded
end is oriented towards the back of the PC board. This diode performs the
function of a varactor diode. A varactor diode acts like a variable capacitor
whose capacitance is controlled by the voltage across it. There is nothing
fancy about the varactor diodes, so we are using a common rectifier diode
as a varactor.
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18. Install R5, 10k ohms (brown-black-orange)
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19. Install R2, 10k potentiometer tuning control.
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20. Install R3, 10k potentiometer volume control. This control varies the
level of audio from pin 4 of the SA602 to the LM386 audio amplifier.
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21. Using a scrap piece of wire, snipped from an installed component,
install JMP-1.
OPTION: with JMP-1 installed the bandspread of your tuning dial is the normal
250KHz. To get more bandspread in the ham band install C14 as shown in the
parts diagram and install R7 (2.2k) in place of JMP-1
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22. Install S1, the power switch.
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23. Install the 9-volt battery snap connector, making sure that the red (+)
and black (-) leads are correctly installed.
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24. Install C7, .01µF ceramic disc capacitor (marked 103 or .01 or 10nF).
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25. Install C8, a small 4.7-10µF electrolytic capacitor. Observe correct