HP first entered the microwave field with signal generators developed for the Naval Research Laboratory during World War II. Production of such generators required test and calibration equipment specific to those frequencies.
A complete line of microwave test products followed World War II R&D.

805B Slotted Line

Impedance Measurement

Among the many microwave measurement accessories that could be listed, one of the most important was the first impedance measuring system.

The combination of the 805A slotted line and model 415A standing wave indicator can be considered to be HP's first microwave impedance measurement system. This was the introduction of a technology in which Hewlett-Packard would be the leader for the following fifty years and which is, still today, an area of leadership for Agilent Technologies.

As listed in the 1950 catalog page 44, the 805 slotted line can be used to measure: - Load impedance - System flatness - Connector reflection - Antenna match - % of reflected power - Standing wave magnitude - Standing wave phase. The 805A usable frequency range is from 500 Mc to 4000 Mc. The 415A Standing wave indicator is a high gain, low noise amplifier operating at the fixed frequency of 1000 cps (modulation frequency of the signal applied to the slotted line). The amplifier output is measured with a square-law calibrated vacuum tube voltmeter which reads direct in VSWR and in dB.

Another important possibility of the slotted line was frequency measurement. Even if the accuracy was very low, other ways of measuring frequency with better resolution, were very expensive at this time. They had to wait until 1955 to find more dedicated wavemeters (see below) to precisely measure signal frequency, the slotted line would stay the lowest cost solution for a few years.

Microwave Market Grows

The microwave product line grew very quickly in the early 50s. Shown below are two of the 6 pages of a 1953 short-form catalog. A new slotted line, the 809B universal probe carriage with interchangeable waveguide slotted sections, raised the measurement range of impedance up to 18,000 Mc. A complete line of waveguide test equipment operating in the 2.6 to 18 KMc frequency range include adapters, couplers, tuners, attenuators, detectors and loads.
Other instruments shown on these pages, like the 430B power meter or the 803A VHF bridge, are described in their dedicated chapters of this Quick Tour

Various Waveguide and Coaxial HP 530 Series Frequency Meters

Microwave Frequency Meter

The first microwave frequency meter production appeared in the 1955 catalog. It is made of high Q resonant cavity mounted on special waveguide section so designed that a small amount of power is reflected at resonance, while the major portion is transmitted.

The 530A frequency meter was the first model produced by HP.
It was available for the waveguide bands:
J (5.3 to 8.2 kmc) - H (7 to 10 kmc)
X (8.2 to 12.4 kmc) and P (12.4 to 18 kmc).
Overall accuracy obtained with these meters is 0.1%

Further evolution of this product line would complete the frequency coverage down to the UHF region with the 536A (left one in the photo on the right) for measurements of 1 to 4 GC on coaxial circuits.

NOTE: The 536A appeared in the 1961 catalog. This catalog was the first which introduced the GC (gigacycle) unit labeling for microwave frequencies.

Cover of the 1961 Microwave Catalog Courtesy of the Hewlett-Packard Company

Instruments and Equipment for
Microwave Measurements,
Dedicated Catalog

An exhaustive listing of the Microwave Product Line available at HP, by the end of the fifties, can be found in this 1961 MICROWAVE CATALOG. Its contents recap all the instruments and accessories available for the measurement of waveguide and coaxial systems by the beginning of the sixties.

Another useful characteristic of this catalog is the method of classification chosen which is that products are classified by their usable frequency range. A number of selection tables give an immediate overview of the various accessories available for each type of measurement, in each type of waveguide and inside its usable passband.

1961 Microwave Catalog ( PDF, 11.3 Mo )