To find out the parameters of JFETs, both n-channel and p-channel, the simple and inexpensive attachment to the voltmeter described below will help, which allows you to measure a zero-gate voltage drain current (IDSS) and a gate-to-source cutoff voltage (VGS(OFF)). Thus, using only this attachment with some kind of voltmeter, you can, for example, select JFETs with the best characteristics or select a pair of JFETs with the same parameters. In addition, the attachment allows you to check JFET for performance, to clear up the transconductance at the intended DC operating point, and for students and novice radio amateurs to examine the field effect transistor in order to better understand its principle of operation.

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An experiment with an audio recording of the reception of a broadcasting radio station in the medium wave band was carried out in order to once again confirm the ability of the anti-noise ferrite rod antenna “Olusha-10” to suppress industrial and domestic radio interference. The principle of operation of the “Olusha-10” antenna is described in detail in the author’s article “Suppression of Common-mode Interference to Radio Reception”.

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In the educational literature, load matching is most often considered in relation to the wave properties of a long line during the transmission of a high-frequency signal. But here the energy relations are considered during the transfer of energy from an active two-terminal network to a passive one.

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After the publication of the author’s articles “Suppression of Common-mode Interference to Radio Reception” and “Master-kit from “SELGA-404” Radio Receiver Parts: Anti-noise Ferrite Rod Antenna “Olusha-T”, the anti-noise ferrite rod antenna “Olusha-10” was developed, which, unlike the antenna “Olusha-T ”, is already an independent product, and not a rework from the parts of an old radio receiver: a printed circuit board was developed, etc. The antenna was made by order of radio amateurs in various versions, including installation on a photo tripod and with a friction vernier mechanism.

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The simple automatic charger we are talking about is assembled from readily available parts, the total cost of which does not exceed the price of a single AA nickel-metal hydride rechargeable cell, which the device is designed to charge. You can assemble it on a printed circuit board, the dimensions of which are not much larger than the dimensions of the rechargeable cell itself.

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To control the temperature at several points using platinum or copper resistance thermometers, a simple and inexpensive eight-channel resistance-to-frequency converter will help, the advantages of which include noise immunity, unipolar power supply and low power consumption.

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The home life of a resident of a modern industrial city is oversaturated with household appliances: audio, video, kitchen, computer, etc. Much of what the city dweller now cannot (or does not want to) do without is a rather powerful source of radio interference, due to which the reception of even powerful broadcasting stations is either very difficult or impossible at all, instead of “live” ether, only a monotonous low-frequency rumble and crackle is heard, regardless of the frequency to which the radio is tuned. This is especially noticeable in the ranges of long and medium waves. The article “Suppression of Common-mode Interference to Radio Reception” not only outlined a method to suppress such interference, but also described the design of a layout of a symmetrical ferrite magnetic antenna for the medium wave range, which allowed the author to receive signals from far distant broadcasting stations in an apartment of a reinforced concrete panel house. Below we will talk about how to make such an antenna from some old radio.

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