(microyao Note: This map output amplifier stage can be used for C1971 RF power amplifier driven by class)
(microyao Note: In this edition of previous postings. I have published an original stereo FM transmitter, that the circuit to achieve a more simple, just use the Japanese company's BH1415F chips while Roma have been. that the circuit using this circuit The output stage further promote the C1971 is very easy to reach more than 5W of power, if the last stage then two C1972-power synthesis, can reach around 30W of power! in this power, the antenna side is placed on a 60W light bulb can be lit!)
This station FM transmitters produce a rather unusual one not carved circuit boards, there is no circuit diagram is also no access to two or three if the wrong one installed on the welding OK no matter how power can be achieved for more than 600MW, how, interest you?
No BS, you can now look at the following assembly diagram (principle of no speaking, one step is faster point?)
(This figure Click to enlarge view)
(microyao note, the varactor must use good quality, sound quality and large offset on the point relied on by)
Description:
1: Oscillation-level use of "Colpitts" oscillation circuit, do not look it is also the LC oscillator, but this LC either-LC, can not afford and other FM confuse the stability of the circuit, hand touched or people close to the point of run that the frequency of there is no such thing.
2SC1907 be completed by an oscillating tube, COILA and its left 10PF above, as well as jointly determined the fundamental frequency of the circuit. Audio modulation from the completion of varactor diodes, but also through a 47 - 270K plus a resistance to it by the beginning of voltage linearity better points. "Colpitts" oscillator circuit stability, thanks to the figure of that 33PF, it and other key parts of the circuit LC relative "isolation" open to.
2: Post-class C2053 buffer selected frequency C1970 Amplifier, 1W output impedance of exactly when the C1970 Europe in the 50 or so, Oh, impedance matching circuitry are all saved. Behind the COILC and capacitance are "pass-band filter," to avoid too much clutter you have trouble finding someone else.
3: The circuit board PCB How can this be done? Center was an assembly diagram to see a box yet? It actually is two-sided PCB board cut a small block, side and motherboard welded shut when the fixed use, the other side take the welding parts, anyway, not many spare parts, must you?
4: all parts of the parameter values do not mistake short legs and get enough points on the line of welding up of small ceramic capacitors to use the kind of high-frequency red dot, green and the other parameters of what is not accurate, welding finished checking errors and omissions can be no power a.
10 million, I remember that before the power cord to the antenna termination to load the root, or else C1970 After several moments on the burnt! What a power meter or other instrument to tune the best, however, and not, to find a small bulbs should be 1.25V75MA the kind of low-voltage low current, + - 60CM pole then the root length of wire into something round about near the transmitter. Debugging is relatively simple, direct power, total current should be less than 300MA, light bulbs are bright, basic OK, all the circuits need to be adjusted only COILB and C, adjust the target, the small bulbs the brightest.
The reason why this circuit is that reliable and easy to secure its own equipment, the circuit has basically decided on the broad parameters - even if only adjustable inductor B and C, after the circuit Zhuangwan not around before the wrong words without adjustment, the circuit can also be exporting radio, adjust or not adjust the power and the difference is the size of the clutter problem.
In addition, the antenna elevated far away from the circuit should be used when the cable connection.
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