The phrase "a frequency that was" is correct and usable in written English.
It can be used when discussing a specific frequency that existed or was measured in the past.
Example: "The study focused on a frequency that was prevalent during the early 2000s."
Alternatives: "a frequency that existed" or "a frequency that occurred".
If the signal is coming from the lander, scientists say, it is being transmitted through a small antenna at a frequency that was designed for communications with the Mars Global Surveyor in orbit a few hundred miles above the planet.
I was watching at a frequency that was probably a little weird for a young grad.
Before anti-CD20 therapy, 184 IgG+ GAD65-specific cells per 106 IgG+ memory B cells were found in twin A, a frequency that was almost identical to that in healthy controls (183±42 GAD65-specific IgG+ per 106 IgG+ memory B cells).
These included 0.125 kHz, a frequency that was not studied in ALSPAC (p = 0.0008432, see Additional file 1).
In the control group, CYP1A1*2A had a frequency that was uncommonly high for Caucasians (8.5%, p < 0.01 vs other Caucasian populations [ 14, 26]).
That group developed paracentesis-induced circulatory dysfunction with a frequency that was significantly higher (33.3%) than that of the patients allocated to hyperoncotic albumin (11.4%).
You tune your radio to a frequency that is not occupied by a station or has one with a very faint signal.
Mobile devices themselves can also be equipped with special sensing circuitry to detect what frequencies other cellphones are using, and to choose a frequency that is less crowded, he said.
Because the services we rely on are letting us down with a frequency that is simply unacceptable.
The new model also transmits at 406.04 MHz, a frequency that is now monitored by orbiting satellite.
Male patients are demanding alloplastic facial augmentation with a frequency that is increasing annually.
