Jednoduchý FM VKV vysílač

Jednoduchý FM VKV vysílač
Vydáno dne 02. 04. 2011 (453 přečtení)

aneb spíše jako zdroj signálu na zkoušky přijímače

WEEKCIRC Myslím, že tohle nemusím ani překládat, jinak mám dojem, že jsem to našelkdysi
v Holandsku na nějaké Cb paket bbsce.

Logicky se tím taky nemá vysílat, uvádím to né jako vysílač, ale zkušební zdroj
signálu, že...

Circuit of the Week Quality FM Transmitter

This FM circuit uses a medium power VHF oscillator built around BC548
transistor. The BC series transistors are generally used in audio low
frequency stages. But as per databooks their maximum operational frequency
is 200-250 MHz.
These can oscillate well in VHF range. A varicap based circuit is used for
good quality frequency modulation. Operational frequency can be altered by
adjusting spacing of coil L1. Coil L1 consists of four turns of 20 SWG
wire, space wound air core. Antenna tap is taken at one turn from bottom
end. By using 70cm single-wire arial, range of up to 200 metres may be
expected. The range can be extended by using a multi-element ground plane
antenna. Length of each pole is 70 cms for 100 MHz frequency. Vertical pole
is the active radiator. All radials are shorted and connected to ground of
PCB. Output power of the transmitter can be raised by lowering value of
resistor R5 connected between emitter of transistor T1 and ground to, say,
47 or 39 ohms. However, if its value is reduced below 22 ohms, the oscilla-
tions may stop altogether. Use 9-volt rectangular PP3 compact battery.
Complete transmitter with battery can be housed inside a cigaratte case.
For good frequency stability, it is advised to house transmitter inside a
metal case.

( Celý článek | Autor: Krysatec | Počet komentářů: 3 | Přidat komentář |

)



Dnešní datum: 18. 10. 2014	\| Hlavní stránka \| Seznam rubrik \| Download \| Weblinks \|