1. FREQUENCY CONTROL MODES OF ET 91 To learn more click on note! END to END Loss Measurement Group Delay Distortion Measurement Frequency Tracking with Sweep Fr receiver = Carrier ± Fr transmitter Conventional Control Modes Special Receiver Control Modes Measurements with MTTS Frequency Modification with Cursor Keys Frequency Setting with Number Keys Fr receiver = Carrier ± Tone ELEKTR NIKA

2. Frequency Setting with Number Keys To set a new frequency use the NUMBER keys as usual. E.g. 3825 Hz Notice: don’t touch the cursor keys ELEKTR NIKA

3. Frequency Modification with Cursor Keys The frequency STEP can be selected with the HORIZONTAL cursor keys The FREQUENCY can be modified with the VERTICAL cursor keys FREQU: 100.000 kHz FREQU: 100.100 kHz FREQU: 100.200 kHz Notice: don’t touch the number keys Modification of frequency in 1Hz, 10 Hz 100 Hz etc steps. ELEKTR NIKA

4. Selectable ranges Frequency Tracking with Sweep ELEKTR NIKA

5. Receiver Frequency Setting in Carrier ± Tone Format Set carrierSet tone Select mode Test instructions of FDM systems often specify the test frequency in format: Carrier ± Channel ( Tone) Frequency. ET 91 provides the separate setting of carrier and tone frequencies and so: No frequency calculation is required! Final display format ELEKTR NIKA

6. Special Transmitter Tracking Mode During the test of FDM equipment often required a special transmitter tracking when: ■ audio frequency test signal is applied to the input of tested channel and ■ the modulated high frequency signal is measured In that case: Receiver Frequency (Rx)= Carrier ± Transmitter Frequency (Tx) In special transmitter tracking mode of ET 91 two parameter can be set: ■ the frequency of transmitter between 200Hz and 4 kHz in 1 Hz steps and ■ the carrier between 1kHz and 2400kHz in 1kHz steps The test frequency of level meter is automatically set ADVANTAGES: No frequency calculation is required ! In case of test series only one frequency setting is required ! ELEKTR NIKA

7. END to END Loss Measurements with MTTS MTTS METHOD: ■ The transmitter generates 35 test tones ■ The receiver measures the 35 test tones simultaneously ADVANTAGES: ■ No synchronisation is necessary between the two instruments ■ The measuring time is shorter than that of other methods ELEKTR NIKA

8. Group Delay Distortion Measurement with MTTS MTTS METHOD: The transmitter generates 36 test tones ■ Frequency range: 100 to 3600 Hz ■ Frequency step: 100 Hz ■ Level: -20 dBm / frequency The receiver measures the 36 test tones simultaneously ADVANTAGES: ■ No synchronisation is necessary between the two instruments ■ Group delay and signal level measurement at the same time ■ The measuring time is shorter than that of other methods ET 91 applies the multi tone test method described in Recommendation ITU-T O.81 Appendix I ELEKTR NIKA

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