It’s the “no probes” part that’s the killer here. The probes are what gives the meter its bandwidth. Probes are usually bad because users like to measure the signal. Schematic of Boonton Model 92 A RF Millivoltmeter; Boonton Electronics Corp. . In the Ballantine Model A RF millivoltmeter, which is. The old Boonton RF Millivoltmeter or Boonton RF Microwattmeter or . Ballantine Labs A Standard RF Probe – 10KHz to GHz with pf.

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Resistors RR63 are selected to provide a constant output impedance. Calibrator for calibration and testing of A. As the input signal exceeds 30 mV rms the response gradually approaches peak-to-peak at mV and above.

Ballantine RF Millivoltmeter 3440A With Accessory Kit

Since this transition region is often an important region for voltage measurement, as are the regions above and below, it is necessary to avoid or compensate for the transition response characteristic as well as to provide the appropriate response in the square law and linear regions.

I just picked up two of these cheap. The other thing is that I seem to recall that the probes are serial number matched to the instrument. Most of these meters were made for the US Government, which seems to be Ballantine’s best customer.

Ballantine RF Millivoltmeter A With Accessory Kit | eBay

Thanks for all the information, these definitely were gov’t, there is a USMC callibration on one of them. You won’t be able to get the engineering and parts required for the bandwidth. I googled RF probe and found lots of information about making a probe for use with a vom or dmm using the 1n34 diode.

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Untested with no probes. A root-mean-square rms response in the small signal region below 30 mv may be obtained by taking the square root of the sum of the squared signal components. The apparatus of claim 6 wherein the diode detector is a pair of germanium point contact diodes in a series configuration. Successive approximation techniques are employed in commercial radio frequency millivoltmeters such as the Boonton Electronics Corp.

Capacitor C17 provides damping on all ranges. Therefore, it may well be worth the time and expense to track down some probes.

Relative gain or loss measurements are simplified by a 0 dB reference adjustment. In the Ballantine Model A RF millivoltmeter, which is constructed generally in accordance with the embodiment described here, the probe housing is heavy brass with a double wall, to prevent localized external temperature variations from changing short term calibration by providing a long thermal time constant.

Antique Radio Forums • View topic – Ballantine A RF millivoltmeter

The output of the detector is filtered millivoltmetef a filter formed by resistors R1-R4 and capacitors C2-C5. When remote programming is employed, the manual range control switch S2 is disabled by a signal applied to pin J6. Users browsing this forum: Some of the old Millivac RF voltmeters MV series, for examplecould get down to the single millivolt range with nothing more than crystal detector probes.

Transistor Q2 is a grounded emitter power amplifier which is used to vary the collector voltage of Q1. In the 10 mV range, a further reduction is provided by substituting resistors R85 and R87 for resistors R84 and R86 in the voltage divider. Showing results 1 – 9 of 9 products ballantkne.

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For baallantine typical RF diode detector of the type used in RF millivoltmeters, a square law response or transfer function is obtained for signals below approximately 30 millivolts mVa linear response or transfer function is obtained above approximately mV, and the response between approximately 30 and mV is in transition between square law and linear.

My Boonton’s use special diodes in the probe for full-wave rectification, which is then converted back to AC in the instrument via a mechanical chopper. RF voltmeters without probes are truly a dime a dozen. Lead is connected to the main ground of the millivoltmeter.

The precision resistor network comprising resistors R52, RR63, plus the feedback network of meter amplifier U9, performs the required scale linearization. The apparatus of claim 5 wherein the diode detector is a germanium point contact diode. Where k is the mixing factor determined by a given position of the range select switch SW, EQU4 As a result, the output voltage V o of the meter drive 34440a can be defined as follows: Well considering I paid 5 bucks for the pair, I won’t loose any sleep over the rather bleak probe situation.

The Ballantine A still appears to be a current instrument, and ballnatine rather nice one. Several types of such detection circuits are known.