This is a very simple cable TV amplifier using two transistors. This amplifier circuit
is most suitable for cable TV systems using 75 Ohm coaxial cables and works fine up to
150MHz. Transistor T1 performs the job of amplification. Up to 20dB gain can be expected
from the circuit.T2 is wired as an emitter follower to increase current gain.
Notes.
The circuit can be assembled on a Vero board.
Use 12V DC for powering the circuit.
Type no of the transistors are not very critical.
Any medium power NPN RF transistors can be used in place of T1 and T2.
This is just an elementary circuit. Do not compare it with high quality Cable TV
amplifiers available in the market.
Read more: http://www.circuitstoday.com/cable-tv-amplifier#ixzz1PHLHQPsR
Am Receiver Circuit
Here is a low cost AM receiver circuit that can be tuned from around 550 to
1100 KHz. Three transistors are used in this project. The transistors Q1 and Q2 are
wired as a compound transistor pair in which Q1 is an emitter follower and Q2 is a
common emitter amplifier. The emitter follower prevents the loading of tank circuit,
while the common emitter amplifier necessary voltage gain. The L1 and C2 forms the tank
circuit.The L1 also does the job of antenna.The series combination of R6 and R7 gives a
regenerative feedback between output of the Q2 and tank circuit. The transistor Q3
performs the demodulation of the carrier signal. It also provides amplification the
demodulated signal. The audio output is coupled out from the collector of Q3 via the
capacitor C3.Capacitor C6 provides some noise filtering. Circuit diagram. Notes. The
circuit can be assembled on a general purpose PCB. Use a 9V PP3 battery for powering the
circuit. R7 can be used to adjust the sensitivity and selectivity of the circuit. A high
impedance head phone can be used for listening the radio. For L1 make 60 turns of 26 SWG
enameled copper wire on a 3/8…
Read more: http://www.circuitstoday.com/category/radio-circuits#ixzz1PHJxCcCE
