BFO is a simple device which helps us to listen SSB and
CW transmissions. Reception of SSB and CW signals requires a product
detector or BFO (Beat Frequency Oscillator) to reinsert the missing
carrier. This circuit is very simple since it requires no turned circuit
and hence no adjustment in the BFO circuit. The number of components
required is also very limited. To produce 455 Khz carrier a ceramic
filter is used. It cost me Rs: 6/- only. The RF choke (RFC) is made
by winding 150 turns of enamelled wire on half watt 150 K carbon resistor.
When receiving Single Side Band (SSB) signals the locally
generated carrier beats with the SSB signal to produce the complete
audio signal. Because the ceramic filter operates at fixed frequency,
no turning is required to demodulate the single side band (SSB) signals
and no regulated power supply is necessary. First tune your AM radio
to some SSB signal and switch on the BFO and slightly adjust receiver
turning for good resolved audio quality. To resolve stronger stations
connect a wire not bigger than 10 cm to the out put of the beat frequency
oscillator.
Most of the BC receivers use 455 KHz as IF amplifier
frequency. Some receivers have an IF Frequency which lies between
450 and 460 KHz. For best result the receiver IF amplifier frequency
and the beat frequency oscillator frequency should be the same.
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7 MHz SSB Transceiver
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Linear Amplifier
used in 7MHz SSB Ham Radio Transceiver using 2N2222A, SL100B and BD139 |
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Hobby Circuits - Ham ( Amature ) Radio |
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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. |
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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. |
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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. |
