Part 3 of the item VFO (simple one). The importance of electromagnetic shielding of the VFO (and other radio units) to prevent problems. Especially oscillations and instability, caused by straying electromagnetic waves to locations where they may not be found. Perhaps not so clear: under the plywood plate there is tin-plate glued and nailed. This functionates as “earth/mass” and is connected to the earth/mass/minus/shielding of the radio units above. When you watch this video on another …
The importance of a good quality tuning capacitor for the antenna coil. For VFO and antenna coil an air type tuning capacitor made from aluminium-like or brass-like metal works well. The shaft/knob of the tuning capacitor must be on ground to prevent hand effect when tuning, the turn should be sufficient (360 degrees). Note that less capacitance should occur when you turn the knob to the right, if not the frequency scale will be reversed. Normally the higher frequency is on the right side …
Part 2 of the item “VFO” (simple one). Corrections to the video: “capacity” must be “capacitance”. “Sensive” = “sensitive”. When the frequency of the VFO changes, you have to tune in again to find the radio station, this is what I mean. The item of the hand effect on the front of the VFO is perhaps not so clear. I mean this: the thin copper layer conducts electricity. Although the mass of the receiver is on minus/ground potential, it is possible that your body, touching the receiver by hand …
Constructing tips for building a superheterodyne shortwave radio. In this part: quality of the tuning capacitors (fine tuning and mains tuning) of the VFO (variable frequency oscillator). The used foil type capacitors are more sensitive to temperature changes, thus frequency changes. They also have a “sharp” tuning characteristic and the turn is (too) short when used for a broad frequency band. It is also possible that the shaft is not on ground, this can cause hand effect (= the frequency …
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