Post #2095111

The ionosphere's height is changing quite a bit during the course of a day. E.g., after sunset, I understand the ionosphere becomes cooler and hence somewhat collapses downwards, which increases ion concentration. So the MUF descent after sunset is sometimes arrested for an hour or so. Check the MUF 3000 graphs of https://www.ionosonde.iap-kborn.de/actuellz.htm#muf Such movement should generate Doppler effects. Whether other mechanisms might also introduce frequency shifts, I don't know. @Quantensalat