Filter
Top Products
HR20• 11
RECEIVER ASSEMBLY:
1. Install the RCA antenna jack, J1. Solder all four points.
2. Install C5, a .01µF ceramic disc signal coupling capacitor . This
capacitor brings the signal up to the front of the PC board. Notice the long
PC trace from J1 through C5 to R1.
3. Install potentiometer R1, the RF gain control. Insert it into the PC board
so that it seats firmly and is straight and even. Solder the three pins and
the two mounting tabs.
4. Examine inductor L1. Look at the bottom side and you’ll see a small
silver and brown tubular part nested within the black plastic base. This is
actually a ceramic tubular capacitor! It resonates with the tuned circuit for
for 10.7 MHz. This is the wrong frequency for our purposes so we’ll simply
remove it and add our own external capacitor (C13). Removing the tubular
capacitor is not as hard as you might expect, simply crush it completely
with a small screwdriver or knife. Omitting this step will prevent L1 from
peaking on 20 meter signals.
5. Install L1(marked 42IF-123), which tunes or preselects the signal input
from the antenna through C5 and R1.
6. Install C13, a 27pF ceramic disc capacitor (marked 27 or 27K).
7. Install U1, the SA602 IC mixer-oscillator. The marked end of the IC
(band or dot) must face the FRONT of the PC board. If you wish, install an
8-pin DIP socket, still remembering to orient and install the SA602
correctly. Please don't be afraid to solder U1 directly to the board as we
have seen more repair problems with DIP sockets than from direct
soldering of IC chips.
The parts we have put in so far bring the signal from the antenna jack up to
the RF Gain control (actually the RF attenuator) and to a tuned circuit
composed of L1 and C13. Inductor L1 allows us to match and tune the 20
meter band signals to the SA602’s input.
8. Install C6, .01µF. This capacitor bypasses pin 2 of the SA602 to
ground. Bypass means to provide a nice low impedance (impedance
means AC resistance) path to ground.
9. Install R4, 270 ohms (red-violet-brown), which drops the 9 volt battery
supply to 6-7 volts, safe for the SA602.
10. Install D2, 6.2 volt Zener diode. This is the smaller of the two diodes
and has a painted glass body. This diode acts as a voltage regulator by
keeping the voltage across it constant.
11. Install C10, a 100-220µF electrolytic capacitor. Electrolytic capacitors