Boonton Radio Corporation 100-A Q-Meter sn358.

This is the first Q-Meter sold by Boonton and dates to the middle of the 1930s. In good cosmetic condition, for parts or repair--not safe for Use.
Beschikbaarheid:: Op voorraad

The Boonton Model 100-A is designed for testing Capacitors and Coils in order to determine their relative "Q Factor" where Q has been defined as the "quality factor of a tuned circuit".   The Q of a circuit, whether electrical or Acoustic, is measured by the narrowness of its bandwidth; the higher the Q Factor, the narrower the bandwidth of the circuit. 

Boonton Radio Corporation of Boonton NJ manufactured a variety of electronic test equipment beginning in 1934.  

The cosmetic and physical condition of this unit is good to very good, with some deterioration of the plastic dial markers, one of which has been repaired (see photo).   There is also evidence of a repair or modification by a previous owner (see photos), specifically the replacement of a large filter capacitor in the power supply module, replacing the original power cord and installing a grounded plug on a 2 wire cable.    

Defects of note:

  • small red discoloration on parts of the 2 large metal dials
  • a repaired crack to the capacitance dial marker
  • scratches and defects to the black paint finish
  • missing screws to back cover, top terminal mount
  • filter capacitor terminals & wiring are a shock hazard

****This Unit IS NOT SUITABLE FOR USE.  It is being sold for display purposes only.****

The unit has been powered up, and the 2A6 and 80 tube filaments do light up.  No direct measurements of any Capacitors or Inductors was made, and no other tests beyond checking the visible tubes filaments and noting some meter activity were observed. 

We don't have any technical data specific to the Model 100-A, other than a few references included below.  Here is some history of the company and its well received product line.


The Boonton Q-Meter Type 100-A covers 50 kc (kHz) to 50 mc (MHz). The direct reading calibration of the meter is correct within 1 %. The accuracy of measurement for all ordinary components is accurate to 5 per cent at any frequency up to 15 mc. Two scale ranges are provided, from 0 to 250 and 0 to 500. The instrument is for 110 volts, 60 cycles, with a current consumption of ca. 50 watts. The model type 100-A is the first Q-Meter at all and the first instrument of Boonton Radio Corp. The market introduction was May 1935 for $450.

Q-meters measure the quality factor of coils and other components used in electronic devices and had broad applications in the testing of components and systems.

The direct successor to the 100-A is the Boonton Q-Meter 160-A - with its "sister model" 170-A

"Other Early Ac Instruments: Perhaps the most famous RF measuring instrument was the Boonton Radio Company's Type 100A "Q Meter" designed by C.J. Franks and W.D. Loughlin and introduced in 1934.
This popular instrument went through many revisions over the years with the BRC types 160-A appearing in 1939 (see figure 2-36) and 260-A in 1953 being the best known. Hewlett-Packard, who bought BRC, listed the type 4342A Q meter in its catalogs through 1993. In this circuit the unknown inductor is resonated against a variable capacitor whose dial reads inductance directly at certain frequencies and the inductor's Q value is proportional to the resonant peak voltage and is read on the scale of a vacuum-tube voltmeter."


Early History

The company was founded in 1934 by William D. Loughlin and others in Boonton, New Jersey. The company developed and manufactured many innovative instruments, the most significant (and earliest) being the Q meter. The instruments they developed were mostly used for measuring for radio technology.[1]


In 1959, Hewlett-Packard purchased Boonton Radio Corporation as a "wholly owned subsidiary"[1] and continued to sell a number of its products, including the RX meter.[2] Boonton Radio Corporation was the second acquisition HP made.