For a project involving an harmonic mixer, a strong and quiet – low phase noise – local oscillator is required. Looking around, I found a 5086-7259 in one of my boxes, a popular part, used in some high-quality HP test equipment.
Unfortunately, no data around, and this might also be the reason why these often go for about 50 USD on xbay.
After some study of the circuit, here a rough schematic. It is essentially a set of Zener diodes and filter caps, plus some high-quality resistors.
The thing needs a +20 Volt, and -10 Volt supply. Not a problem – typically, this would be provided by dedicated low noise regulators, from the 24/28 V and -15 V rails common in test equipment.
Some measurement of the tuning current – it needs about 42 mA at 1.8 GHz (seems to work below the specified 2 GHz), and about 110 mA at 4.6 GHz – therefore, sensitivity as about 43 MHz per 1 mA.
Doing a quick calculation – setting the frequency to 1 MHz will required a DAC of about 12.5 bits resolution. Using a 16 bit DAC for the coarse tune current will be perfect, about 70 kHz per LSB; with phase lock on the FM coil.
The output power is quite substantial, about 15-18 dBm. Here, operated at the low end of the range, about 16 dBm:
