DIY make a straight up double-tuned radio yourself

Chinese New Year nothing to do, the big brother to the altar to learn to do radio play. Case is 30 years ago the antique, still above the Quotations from Chairman Mao.



What is the circuit considered the election a long time, the old circuit is also made now only a "high imitation" fake antiques. I like the new character things, like creative things. So he decided to design their own circuits, transistors and integrated circuits for a dual-tuner high-level radioactive mixed-type radio. Circuit as follows:

Simple adjustment of high-level radioactive radios for amateur production. IC1 is a radio-specific amplification circuit, a similar model also BS414, IN414, MK484, NT484, etc.. W1 is a high level manual gain control, it can effectively control the release of high-level gain. W2 is the volume control. 270p constitute double with double-loop tuning variable capacitor, double-loop tuning is to increase the selectivity.
As is the case with a pocket, can only 10X100 the ferrite magnets. In order to improve the efficiency of magnets, and used by the two magnets, which is equivalent to 10X200 the bar magnet. Magnetic antenna line with the 0.07x28 round sub-system, very early 25 +15 ring, plays a very 6 to 8 laps. To improve the Q value, the coil winding process to make use of chaos. B1 with TTF-2-9 in the week of conversion, 80 +40 ring very early, sub-polar 25 laps.
Green LED power indicator and the tuning plate to do lighting, as well as both regulator.
In order to increase ease of use in the tuning knob on the gear, tuning knob rotation nearly double. In order to reduce the wear volume control potentiometer, additionally, a power switch. Similarly, for easy maintenance, speakers, headphones jack and power switch are used for wiring plugs, sockets connected.
Bottles and unexpectedly good results. High sensitivity, low noise, little noise when the transfer station. Good sound quality, external computer speakers have a "Puff" sound. Local radio and FM radio quality sound the same.
Drawback is that selective Chaliaoyidian, to close weak to Taiwan has a strong platform for sound mixing.

The machine's sound quality is also very good, mainly due to direct discharge type of radio bandwidth than heterodyne type to wide. Also, no mirror, and what difference frequency interference. My experience is to maximize the efficiency of magnetic antenna, the antenna is a passive magnetic device itself will not produce noise. Improve the efficiency of magnetic antenna is much better than the more an amplification effect. Separate zoom levels, to reduce mutual interference, can effectively reduce the noise.
After the machine by installing the units finally understand what is meant by a return to.
The question now is how like to improve selectivity. Hope online you big brother, the brothers who provide valuable experience.



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