A side discussion around an answer to the question How many stations could one hear with an AM/FM radio in front of the ISS' cupola window? has arisen with regard to the possibility that a change in frequency of order 2.6 kHz would need someone to turn the knob of an FM broadcast receiver carefully to track it, or whether a rudimentary PLL or other circuit might have been able to allow reception.
The radio in question (shown below) had only 9 transistors, and covered both the AM and FM bands.
So there are really two parts to this question:
- Could a 9 transistor AM/FM radio implement something that could be called a phase-locked loop?
- Could a 9 transistor AM/FM radio provide good reception if the broadcast drifted by 2.6 kHz due to a doppler shift? (The receiver would be in low earth orbit, presumably intercepting a lobe or side-lobe of the transmitter.)