A Simple VHF Receiver
Using the Dot mode, the receiver
draws 39 milliamps; while using the
Bar mode, the receiver can draw up
to 105 milliamps.
■ FIGURE 9. Receiver inside
Figure 4 shows a parts placement
diagram of the MC3362 PCB (printed
circuit board). Figure 5 shows a parts
placement diagram of the audio,
squelch, and part of the S meter
display drive circuitry. Finally, Figure 6
shows the parts placement for
the LED display and LM3914 driver
Figures 7 through 10 show various views of the completed receiver.
Figure 11 shows a photo of the
only fabricated coil needed for the
receiver. It is wound using 20 gauge
enameled copper wire wound over
the shank of a 7/32 inch drill bit.
There are six complete turns which
will be 1/4 inch in diameter after
being removed from the drill bit. The
turns are separated until the winding
is 3/8 inch long. This coil is L1 as
shown in the schematic diagram and
parts placement diagram of the
MC3362 PCB of the receiver. Note
the leads on this coil are at least
7/16 inch long to insure it is at least
3/8 inch above the ground plane of
There are .bmp image files available which can be used to create
PCBs for this receiver project. These
files are on the Nuts & Volts website
and need to be printed at their original
size to insure the mounting holes
match the parts. Note the distance
between IC pins is .1 inch, while the
width between the IC pin rows is . 3
After all three PCBs are completed and etched, the parts for the
MC3362 PCB may be attached
and soldered. Before installing the
MC3362 IC, insure there are no shorts
to any of the pins, and also insure the
proper voltages appear at each pin.
This can easily be determined by referring to the schematic of the MC3362
portion of the receiver.
Remove the power and install the
MC3362 IC. Reconnect
the nine volt source.
There should not be more
than a 10 to 15 milliamp
current drain from the
nine volt source. I recommend putting a 100 ohm
resistor between the nine
volt source and the
power input to the PCB. If
the voltage drops more
than a volt into the PCB,
then there is probably a short or a
mistake on the board.
If all is working well, you should
be able to hear a strong audio hiss
from pin 13 of the MC3362. That is a
good indication the board and IC are
working. At this point, you may
wish to connect the two tuning
potentiometers (R11 and R20 in the
schematics), and attempt to tune in a
station. A good one would be the
NOAA weather station in your area.
They are usually at 162.4 MHz. I can
easily receive the one in this area
transmitting at 250 watts from Mt.
Pisgah (western North Carolina).
I did not have to tune the yellow
slug in the 455 kHz IF transformer; it
worked well without any adjustments.
If you feel the need to adjust it, without any signal, tune it for maximum
hiss from the speaker, but not more
than 1/8th of a turn either way.
Proceed with the parts placement
and soldering of the remaining PCBs,
carefully checking for shorts and
correct voltage levels before installing
any of the ICs.
The Parts List shows a
simple aluminum box, 6” x 5” x 4”.
However, you may wish to use
something you already have on hand.
I used a recycled box I had from a
previous project. The placement of
the PCBs is not critical, but insure that
L1 is as clear as possible from any
metallic surface. It will be a good idea
to give yourself enough room to put a
fairly large knob on the main tuning
control since even a small movement
of this control will tune the receiver
across many MHz.
Once you have completed the
mounting and connection of all the
PCBs together, connect the nine volt
power through a 24 ohm resistor. If
there are no problems, you should see
at least eight volts on the output to the
receiver. With the squelch knob
turned all the way counter-clockwise
and the volume knob at its midpoint,
you should be able to hear a loud hiss
from the speaker. If you are satisfied
that all is okay, then remove the 24
ohm resistor and connect the nine volt
■ FIGURE 10. Receiver close-up view.
■ FIGURE 11.
July 2007 51