These are variable inductors used for trimming specific frequencies. Usually, you also need an oscilloscope for repairing and re-aligning these old receivers. Here's a YouTube channel that specialises in doing exactly that: MrCarlsonsLab

Alternatively, you could measure every component in the circuit with a precise multimeter and figure out what the value you're supposed to set these at by understanding what particular frequency the component arrangements are filtering out. Here are some online calculators for simple frequency filters:

https://electronicbase.net/band-stop-filter-calculator/

http://sim.okawa-denshi.jp/en/Fkeisan.htm

These are variable inductors used for trimming specific frequencies. Usually, you also need an oscilloscope for repairing and re-aligning these old receivers. Here's a YouTube channel that specialises in doing exactly that: MrCarlsonsLab

Alternatively, you could measure every component in the circuit with a precise multimeter and figure out what value you're supposed to set these at by understanding what particular frequency the component arrangements are filtering out. Here are some online calculators for simple frequency filters:

https://electronicbase.net/band-stop-filter-calculator/

http://sim.okawa-denshi.jp/en/Fkeisan.htm

As other contributors have already mentioned, these are variable inductors used for trimming specific frequencies. Usually, you also need an oscilloscope for repairing and re-aligning these old receivers. Here's a YouTube channel that specialises in doing exactly that: https://www.youtube.com/user/MrCarlsonsLab

Alternatively, you could measure every component in the circuit with a precise multimeter and figure out what the value you're supposed to set these at by understanding what particular frequency the component arrangements are filtering out. Here are some online calculators for simple frequency filters:

https://electronicbase.net/band-stop-filter-calculator/

http://sim.okawa-denshi.jp/en/Fkeisan.htm

Hope this helps and good luck!

These are variable inductors used for trimming specific frequencies. Usually, you also need an oscilloscope for repairing and re-aligning these old receivers. Here's a YouTube channel that specialises in doing exactly that: MrCarlsonsLab

Alternatively, you could measure every component in the circuit with a precise multimeter and figure out what the value you're supposed to set these at by understanding what particular frequency the component arrangements are filtering out. Here are some online calculators for simple frequency filters:

https://electronicbase.net/band-stop-filter-calculator/

http://sim.okawa-denshi.jp/en/Fkeisan.htm