![]() You see, in ordinary variable capacitors when you turn the dial, the capacitance increases linearly. Then - like others - I thought that it must be caused by the adroit use of special capacitors. ![]() But on further noodling, this didn't seem to make much sense. How did they do this? How did they escape the dreaded "bunching up?"įor a while, I thought that it might have had to do with the use of the series tuned Clapp circuit. My beloved Drake 2-B and my almost equally beloved HT-37 are good examples. Even on rigs from "back in the day," back when the Si5351 hadn't even been thought of, some LC VFO rigs tuned linearly. Sad.īut there is hope: Not all LC VFOs tune this way. ![]() This problem contributes to the defection of some great homebrewers: They give up on LC VFOs and they switch to digital VFOs. This is especially apparent at the high end of the frequency scale where frequencies (and stations) appear to be severely bunched together, making tuning difficult. ![]() One of the complaints about analog LC VFOs is that they have non-linear tuning - when you turn the dial (usually attached to a variable capacitor) the space between frequencies is NOT constant. Bob's calculator shows good tuning linearity with an ordinary SLC capacitor ![]()
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March 2023
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