A simple sweep frequency generator. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Measuring technology
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Option 1
The circuit provides for the indicated ratings the "swing" frequency from 4 to 20 MHz. The frequency range depends on the ratings of C1, C3, R1, R2, R4. A dual potentiometer is used as R2. A sawtooth voltage with an amplitude of 1,8 V with a constant component of 0,8 V is applied to the control input.
Option 2
Scheme with a "swing" band from 0,3 to 70 MHz. The uniformity of the frequency response of the generator itself is determined by the capacitance and inductance in the emitter circuits of the generator transistors.
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| Random news from the Archive Coffee and tea drinkers are genetically different
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It is believed that the ability to feel a bitter taste protects animals from many troubles - since many toxins are just bitter, and if it starts to taste bitter in the mouth, then what is in the mouth must be immediately spit out. On the other hand, we drink beer, coffee, tea, not at all embarrassed by their bitterness. However, not everyone loves coffee, and it can be assumed that coffee drinkers simply feel its bitter component worse, so that other shades of coffee taste easily outweigh bitterness.
Researchers at Northwestern University and the QIMR Berghofer Medical Research Institute found that coffee drinkers are more sensitive to bitterness, and not just bitterness, but caffeine. The fact is that we have quite a lot of genes encoding bitter taste receptors, and mutations can get into them that enhance or weaken sensitivity to one or another bitter molecule. In particular, it is now known that there are receptors that sense caffeine, others quinine, and still others the synthetic 6-n-propylthiouracil, which is often used when studying the perception of bitter taste. For each of the three types of receptors, mutations have been described that change their sensitivity. It only remained to test whether people with caffeine sensitivities actually drink more coffee.
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Scientists suggest that those who are especially sensitive to caffeine bitterness have managed to love it, because the vivacity that it gives outweighs the unpleasant taste. In this case, the more sensitive a person is to caffeine, the more he will drink coffee. Moreover, tea lovers will love tea because they never learned to love caffeine - because of the relatively low sensitivity of caffeine bitter receptors.
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