Tag Archives: YIG oscillator

A quick look at the HP 5086-7259 YIG Oscillator: 2.0-4.5 GHz, 15-18 dBm

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.

hp 5086-7259 YIG oscillator

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.

hp 5086-7259 schematic (5061-5426 board)

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:

5086-7259 output