The Hewlett-Packard Model 608E and 608F Signal Generators are designed to meet the requirements of precision laboratory work, and yet to be equally useful for general applications in the VHF frequency range. The Model 608E furnishes RF signals from 0. 1 microvolt to 1 volt from 10 MHz to 480 MHz, while the Model 608F supplies RF signals from 0. 1 microvolt to 0. 5 volt in a frequency range from 10 MHz to 455 MHz. The RF carrier can be amplitude modulated by internally generated sine-wave signals, or by externally supplied sine-wave or pulse signals. The Model 608F contains frequency control circuitry which permits the instrument to be used in phase-lock operation with the Model 8708A Synchronizer. This provision provides a stabilized output across most of the range of the instrument, with a drift factor of 2 X 10-7 in 10 minutes. The instruments can be used for troubleshooting, testing, calibrating, measuring standing-wave ratios, and checking antenna and transmission line characteristics. To preserve accuracy, equipment design holds spurious modulation to a low value under all operating conditions. 1-3. FREQUENCY. 1-4. The frequency of the output signal is indicated on a direct-reading dial, the calibration of which is accurate to better than ±0. 5% for the 608E and ±0.1% for the 608F,when the cursor and FINE FREQ adjustments are properly aligned. Calibration accuracy may be improved further by use of a built-in crystal-controlled heterodyne calibrator which furnishes 1 MHz checkpoints from 10 MHz to 270 MHz,or 5 MHz checkpoints over the entire frequency range of the instrument. At any checkpoint the calibration can be set very close to the calibrator accuracy of 0.01%, bringing overall accuracy to at least ±0.05%. Frequency check point signals are obtained when a headphone set (not furnished) is plugged into the XTAL CAL OUTPUT jack. The control for the output attenuator is calibrated in both decibels and volts. When the instrument is connected to a 50-ohm resistive load and power into the output attenuator is exactly at the ATTENUATOR CALIBRATED mark (+7 dB) on the RF OUTPUT meter, the level of power or voltage applied to the RF OUTPUT connector may be read directly on the ATTENUATOR dial with an accuracy of ±1 dB. When connected to a 50-ohm resistive load, the VSWR at the RF OUTPUT connector will not be greater than 1.2 (SWR of 1.6 dB). The signal generators feature automatic output leveling, maintaining the RF output within ±1 dB of the adjusted output. 1-5. MODULATION. 1-6. The R F output signal can be amplitude modulated by internally generated 400 or 1000-cycle sine waves, externally applied sine waves above 1.0 volt rms over the frequency range from 20 Hz to 20 kHz, or externally applied pulses of 10 volts peak-to-peak. When pulse modulated, the signal generators are capable of producing pulses of RF energy as short as 4 microseconds at signal frequencies above 40 MHz, and pulses as short as 2 microsecond above 220 MHz. The degree of sine-wave modulation is continuously variable from 0 to 90% by a front-panel control. All sine-wave modulation of the output signal is continuously monitored and indicated in percentage on a direct reading modulation meter. 1-7. RFI. 1-8. RF leakage is held to a minimum and is such that when the output signal is adjusted for 0. 1 microvolt, the conducted signal leakage at any other front panel connector and the radiated leakage two inches from the instrument are each less than 1.0 microvolt.