Circuit knowledge

Showing posts with label radio. Show all posts

Thursday, September 25, 2014

FM Radio Receiver Antenna Booster Circuit

This affordable FM radio receiver antenna enhancer makes use of the BF324 TO92 type pnp transistor in a grounded-base arrangement.
The circuit can be utilized like a signal booster with VHF receivers whose front end is afflicted with reduced level of sensitivity (like a lot of valved and army supplemental variations). The frequency selection of the preamplifier is approximately from 75MHz to 150MHz.

The 2 inductors in the circuit are do-it-yourself. L1 includes 10 turns of 24SWG enameled copper wire; the inner dimension is 3mm, without any core. Inductor L2 bears 13 flips of the identical wire, as well as an inner diameter of 5mm; without core as above. A building tip: tight-wind the inductors making use of three and 5mm drill bits respectively in the form of momentary cores.

The prototype of the preamplifier was effectively tried with an 88-108 MHz FM broadcast receiver along with a 2-metre VHF ham receiver. The preamplifier consumes around 2.5mA from a 5-volt supply.

Sunday, August 31, 2014

20W BRIDGE AMPLIFIER FOR CAR RADIO

Features:

COMPACT HEPTAWATT PACKAGE
FEW EXTERNAL COMPONENTS
OUTPUT PROTECTED AGAINST SHORT
CIRCUITS TO GROUND AND ACROSS LOAD
DUMP TRANSIENT
THERMAL SHUTDOWN
LOUDSPEAKERPROTECTION
HIGH CURRENT CAPABILITY
LOW DISTORTION/LOW NOISE

Circuit Diagram:

20W BRIDGE AMPLIFIER FOR CAR RADIO

Thursday, August 21, 2014

One Transistor FM Radio

Thi schema is very simple with only one transistor. No need additional active components, but if you want to hear the sound louder, just build another amplifier schema... :)

One

Part designator	Part description
C1a,C1b	10 pf, 50 v, ceramic disc capacitor
C2	22 pf, 50 v, ceramic disc capacitor
C3	RF tuning capacitor
C4	330 pf, 50 v, ceramic disc capacitor
C5,C8	0.001 uf, 50 v, ceramic disc capacitor
C6	0.22 uf, 50 v, film capacitor
C7	0.0047 uf, 50 v, ceramic disc capacitor
C9	22 uf, 16 v, electrolytic capacitor
D1	TL431AIZ voltage control Zener (shunt regulator)
EPH1	High impedance earphone
L2	22 uh RF choke
Q1	2N4416A JFET transistor
R1	470K, 1/4 w, resistor
R2, R3	1K, 1/4 w, resistor
R4	10K, 1/4 w, resistor
R5	1M, 1/4 w, resistor
R6	100 ohm, 1/4 w, resistor
S1	Small SPST switch
screws for C3	screws for mounting C3 (2 needed)
nylon screw	#4 nylon screw used for tuning C3
battery connector	mini battery snap

More instruction how to build this schema, visit this page

Sunday, August 17, 2014

Radio only 1 transistor without electricity

Experts and amateurs have been Experimenting with radios without batteries since the wireless communication started.

In many designs weve seen radios that operate without power, but all are known to use the diode 1N34. (Crystal Radio).

Although significant improvements have increased the sensitivity and selectivity of these system diagram, Performances were limited until new techniques have emerged.

Here we have the first transistor radio that works without batteries, it is powered by random electric fields are everywhere in the atmosphere.

These diagram are relatively cheap to manufacture, have more volume and better reception from the crystal radios.
This schema is a medium wave receiver and attaches easily to frequencies from 500Khz to 11Mhz.
To get good results in the reception of radio stations, we should give great importance to the ground and the antenna.
To listen to distant and weak stations we have to use a battery 9volt parallel with the capacitor C4 with its positive side between R2 and C4.
The coils are in the frequency of 500-1500Khz is tight and closely wrapped.
The coils are in frequency of 1.5-11Mhz is more tighter and more closely wrapped.