Specifications

VCO Tune-port Input Resistance is the input impedance of the VCO's tune
port. This entry must be accurate to within ± 5% when the VCO Tuning
Constant is not going to be measured. When the Tuning Constant is going
to be measured by the HP 3048A, the actual value of the VCO Tune-port
Input Resistance is not critical, and an entry of 1E+6 is recommended.
(The HP 11848A drives the tune port through a 500 series resistor and is
restricted to 20 mA of output current.)
The Peak Tuning Range
The Peak Tuning Range (PTR) is one half of the total (peak to peak) tuning
range defined for the VCO in the Instrument Parameter display.
The Instrument Parameter entries for the VCO Tuning Constant, Voltage
Tuning Range, and Tune-port Input Resistance are used by the HP 3048A
to determine the PTR for the PLL measurement.
PTR w VCO Tuning Constant* „
loaa
> x Voltage Tuning Range
There are three primary considerations for determining the Peak Tuning
Range (PTR) required for your measurement.
• Adequate Drift Tracking
• Sufficient Phase Lock Loop Bandwidth, and
• Sufficient Noise Floor Level
These three considerations must be traded-off against one another to
determine the optimum PTR for your measurement. That is to say,
higher PTRs (recommended for initial measurements) ensure adequate
drift tracking and Phase Lock Loop bandwidths (PLL BW) at the expense
of higher noise floors.
2-18 Instr. Params: $N w/PLL