INFORMATION ON FREQUENCY: The frequency in DR resonators what is a controversial and difficult to establish matter. The verification is performed by each manufacturer in a different way and with different test jig, it follows that the end user will have differences on the frequency. The differences are due also to the manner of use, for example as a cavity filter or oscillating circuit, depending on the type of support used at the base or on the variation of the tuning element and on the shape of the container, etc... We usually perform tests in repetitive way using always the same test jig. For TEM resonators square section the indicated frequency is the maximum theoretical one in an open circuit as if the resonator had no load connected, then the true frequency which is obtained on the circuit will be lower by about 3 - 8% depending on the load of the connected circuit (see DRO on magazines VHF Communications 4-83 and Dubus 1-95).
