A mixer is a nonlinear element that combines two signals.
A mixer has three ports: F1 receives low level signal; F2 is high
level signal (local oscillator) and F3 is the resultant mixer product.
The output of the mixer contains number of different
frequencies that obey the relationship
Where m and n are integers 0, 1, 2, 3,...
There are three types of mixers: single-ended, single
balanced and double balanced. Double Balanced Mixer (DBM) suppresses
F1 and F2 components of the output signal leaving only the sum and
difference frequencies. Double Balanced Mixer provides superior suppression
of the local oscillator and RF signals in the output leaving only
the sum and difference frequencies. This is known as port to port
isolation
MC1496 is an active double balanced mixer made from bipolar
silicon transistors formed into Gilbert transconductance cell. The
internal circuitry of MC1496 DBM is given below.
MC1496 is available in 14-pin DIP package. Brief descriptions
of various pins are given below.
Pin 1 and pin 4 are balanced low-level inputs. Pin 8
and pin 10 are balanced high-level inputs. Pin 6 and pin 12 are outputs.
Pin 5 is bias usually connected to Vcc through a resistor (normally
10k). Pin 2 and pin 3 determines gain of the mixer. The gain will
be maximum when pin 2 and pin 3 are shorted. Gain can be adjusted
by connecting some resistance between pin 2 and pin 3. Pin 7, pin
9, pin 11 and pin 13 are not used.
DC Voltage measured at various pins of MC1496 given below.
There may be slight variation in these voltages due to accuracy of
measuring equipment or components used.
7MHz
SSB Transceiver - Circuit digram and brief description of
7MHz SSB Transceiver for Hams. The circuit is designed around two numbers
of MC1496. It can push around 80 Watts with IRF840 in the final. You can
down load HTML version or the printer friendly word document.
Morse
Code Tutor - A program (23kb) written in C++. Morse code
uses dot and dash for communication. Still it is popularly used for communication
is short wave bands. The Archive contains program source code and executable.
AM
DSB Transmitter for Hams - circuit diagram of simple double
side band suppressed carrier (DSBSC) transmitter for hams. Circuit uses
crystal oscillator, crystal can be switched for multi band operation.
600
Volt Power Supply - simple 600 Volt DC power supply. Convert
230V AC to 300V and 600V DC.
Ham
Radio BFO- circuit diagram of beat frequency oscillator
using BF494 and how to listen amateur radio communication on ordinary
BC receiver.
Miniature
MW Transmitter - circuit diagram of simple medium wave transmitter
using BF494B. This simple transmitter have a range of 200 meters.
807
and 1625 Valves - data on vacuum tubes 807 and 1625 used
in ham radio transmitters. Describes various pin voltages and different
operation modes.
FM
Wireless Mike - low power frequency modulated transmitter
using two transistors. The circuit works with 9v power supply.
60
Watt RF Amplifier - Soild state RF power amplifier using
IRF840. Simple and easy to construct. IRF840 can handle a maximum power
output of 125 Watts.
Simple
RF Power Meter - simple RF power meter cum dummy load for
low power transmitters.
Touch
CPO - touch operated code practice oscillator using popular
timer IC555. Practice Morse code in a different way.
Modulation
Monitor - very simple and useful circuit used to monitor
on air transmission of your low power amplitude modulated transmitter.
Cheap
Crystal filter - Ladder filter using six 4.43MHz Crystals.
Building cheap side band filter for your bome brew SSB Rig.
RF
Dummy Load - make this simple RF Dummy Load for off-air testing
of your radio transmitter.
Mosquito
Repellant - very simple and easy to assemble mosquito repellant
using two transistors and handy components.
Ceramic
Filter BFO- Receive SSB and CW transmissions
on your BC receiver. Simple BFO is build around 455 KHz Ceramic Filter.
SSB
ADAPTOR - Build this simple adaptor to receive single side
band SSB on short wave AM receivers.
QRP
Keyer - very simple keyer circuit using only one transistor.
Designing
RF Probe - make your self simple and heighly useful RF probe.
An essential tool for every home brewer.
Shorty
Forty Antenna - Do you have space limitaion to put a 40 meter
dipole. Try this Compact 40 meter antenna.
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Where m and n are integers 0, 1, 2, 3,...