Four ways to make a short-wave antenna ----- Short-Wave Antenna

Keywords: homemade medium wave active antenna After reading the masterpiece of Car_radio, although it has already ordered a pair to car_radio, I would like to wait for a while, I can't help it itch. After looking for information, I have set a relatively simple and feasible solution, that is, the LF356 is selected. The power of the impedance match is achieved by high-impedance input. To make it, the circuit diagram is as follows: By the way, the LF356 is a JFET input operational amplifier, a common universal device, which is that the input impedance is extremely high, and there is 1 mm OHM (1 after 12 zero). In order to facilitate tuning, the input is connected in parallel with a 1M resistor. In addition, I found that the input signal should not be directly counted. First, the frequency affects the tuning, and the second is that sometimes the signal strength is too large, and some frequencies will result in unstable op amps. Here is a 3-turn isolation coupling coil, and the effect is more ideal. In addition, the power switch and LED indication are added. The 9V battery still does not disable, the resistance of the LED is not too small, generally selects a resistance of about 6K, so that the current is around 1 mA. This circuit is very simple and does not need to debug, and it will become. This is the improved medium wave antenna, using two shoe boxes, the gain of the antenna is higher, huh, huh. Most of the photos, night views, come to a panoramic, the amplifier is very power-saving, only 3.8mA, can be used for a long time. Said so much, look at the effect. Before use, after use, the local signal is basically full, sometimes overload, it is exactly the attenuation of ATS909. The next step is to increase the gain of the amplifier, the improved circuit diagram is as follows, after use, the increase in increased gain is not large, may be the reason for the device itself. The LF356 is generally used in the magnification of audio and low frequency signals, and medium waves may be difficult for it. Considering that the choice of gain is relatively large, higher op amps or discrete components, such as 9018, etc. to improve the effect. BTW, although the principle is simple, but to achieve the purpose of the shoes, it is not that simple, the process accounts for most of the entire product, believes that old kimchi will deeply understand. Here to play an advertisement for a CAR_RADIO brother, the shoes-type antenna is still useful.

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