17-04-2023, 07:56 AM
The old Yaesu FT-480R has a PLL board with three separate PLLs, the UK version has a frequency coverage from 144.000 MHz to 145.999 MHz. The frequency can be selected on SSB in 10 Hz steps. The three PLLs control three crystal oscillators that by tuning the overtone crystals which with the correct combination gives the required transmission frequency. These PLLs are a swine to set up plus the crystals have aged (these radios are 43 years old) Which in turn causes drift as the PLL drops out of lock. The point is there is always an input scenario in this case the the frequency knob, and in the turntable the speed switch and it's fine adjustment. It's possible that asking it to run at 78 the PLL will be out of lock so drift will occur, rest a finger on the platter and give it a bit of breaking effect and see if it slows, normally they don't even with a fair bit of pressure.
