A method for the transmission/reception of RF signals for NMR measurements uses a heat exchanger (1) for cooling heat sources (5), the heat exchanger having a contact element (4.2) for thermal connection between a cryogenic fluid and the heat source, is characterized in that the heat exchanger comprises a container having an interior volume VB into which a first cryogenic fluid F1 that has a liquid component F1L and a gaseous component F1G flows through an inflow conduit (8) and from which a second cryogenic fluid F2 that has liquid component F2L and a gaseous component F2G flows out through an outflow conduit (9). The inflow conduit has a flow cross-section QZ and a circumference UZ from which an associated parameter VZ=4·Q2Z/UZ results, wherein VB>10·VZ, and the outflow conduit has a flow diameter QA wherein QA≥QZ. The contact element is in close thermal contact with both the liquid volume component VL of the cryogenic fluid and with the heat source. A device for setting the inflow quantity of the first cryogenic fluid F1 into the container is provided that ensures a state F1L/F1G>F2L/F2G during operation. In this way, vibrations due to the cooling process can be largely reduced and the consumption of cryogenic fluid minimized.