With an optional RF input prescaler the Analyzer can measure up to 3, 10, 15, 20, or 24 GHz on Input C. These RF inputs are fully automatic, and no trigger setup is required. Set Sample Interval to achieve optimal compromise between resolution (long Sample Interval) and speed (short Sample Interval). The optional RF input C contains a prescaler that divides the RF signal with an integer value (Prescaler factor), to enable the normal counting circuitry to measure the frequency. The Option 10 (3 GHz) divides by 16, and the option 110/xx (10 to 24 GHz) divides by 64.
Figure 14 shows the effect of the 3 GHz prescaler. For each 16 input cycles, the prescaler gives one square wave output cycle. An input frequency of let’s say 1.6 GHz is divided down to 100 MHz and measured by the normal counting circuitry. The display shows the correct input frequency since the microcomputer compensates for the effect of the division factor.
Prescalers do not reduce resolution. The relative quantization error is the same;12-13 digits for 1s Sample Interval (Gate Time). See Table 1 to find the prescaler factors.
| Function | Prescaling Factor |
| All input A, B, D, E, EA, ER functions (up to 400 MHz) | 1 |
| Frequency C (3 GHz) | 16 |
| Frequency C (10, 15, 20, 24 GHz) | 64 |