In 1946 he built the first multi-element astronomical radio interferometer.

In 1959 he developed a round trip transmission technique for phase measurements, which has been used in almost all the radio interferometers in the world.

Large radio interferometers have been used to map the active jets emitted from active nuclei.

Radio wavelengths are much longer than optical wavelengths, and the observing stations in radio astronomical interferometers are correspondingly further apart.

Some early radio interferometers operated as intensity interferometers, transmitting measurements of the signal intensity over electrical cables to a central correlator.

Further, they can be observed with radio interferometers which can measure very small angular motions.

Jennison saw greater potential for his technique in radio interferometry, and proposed that it should be tested on a three-element radio interferometer at Jodrell Bank.

In 1958 he demonstrated its effectiveness with a radio interferometer, but it only became widely used for long baseline radio interferometry in 1974.

On October 4, 1957, the very evening of the launch of Sputnik, students and faculty met at the Observatory and constructed an improvised radio interferometer.

With the seven feeds it is also possible to detect structures which are too big to be seen with radio interferometers or single-pixel detectors.