Sunday, 13 March 2011
EI9GQ's SIMPLE 80m TX
C1 = 47PF : C2, C3 = 1500PF : C4 = 0.01mfd : C5, C7 = 0.1mfd : C6, C12 = 0.047mfd : C8, C10 = 820PF : C9 = 1500PF : R1, R2 = 5K1 : R3, R5 = 100R : R4 = 180R : R6 = 1K2 : RFC = 22 MICROHENRIES (APPROX) : L1,L2 = 2.2 MICROHENRIES (21 TURNS ON T50-2) : T1 = 2N2369A : T2 = CB OUTPUT TRANSISTOR (2SC1237 OR SIMILAR) : XTAL 3.579MHZ (CHEAP COLOUR TV CRYSTAL) OR 3.560MHZ (QRP CW FREQUENCY)
This simple circuit will give about 1.2 Watts of output when powered from a 13.8VDC supply. If you don't have a 2SC1237, try any other 12V CB radio output transistor 2SC1969, 2SC1307 etc. The value of RFC is not critical, 10 turns on a high permeability ferrite toroid core works fine. I used a DPDT switch for the RX/TX switching, one pole for the aerial (antenna), the other pole to switch the 13.8V supply.
Saturday, 12 March 2011
Friday, 11 March 2011
AM/FM/SW active antenna
This circuit shows an active antenna that can be used for AM, FM, and shortwave (SW). On the shortwave band this active antenna is comparable to a 20 to 30 foot wire antenna. This circuit is designed to be used on receivers that use untuned wire antennas, such as inexpensive units and car radios. L1 can be selected for the application. A 470uH coil works on lower frequencies ( AM ). For shortwave, try a 20uH coil. The unit can be powered by a 9 volt battery. If a power supply is used, bypass the power supply with a .04uF capacitor to prevent noise pickup. The antenna used on this circuit is a standard 18" telescoping type. Output is taken from jack J1 and run to the input on the receiver.
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