[R-390] Millivac RF Voltmeter help

Fri, 30 Aug 2002 20:35:22 -0400

Hi,

Later on these guys got bought out by Boonton. The Boonton RF milivolt
meters are direct descendants of the unit you have. The circuits in all of
them are fairly similar. I do not have data on the exact unit you have but
here's my guess:

Frequency range to 1 GHz
Input impedance > 5 K ohms , less than a pf or so

The screw on tips should be easy to find since I have only seen one type.
The hard part is getting a unit with the probe still on it. They matched the
probes to the instruments so a late model probe probably will not work right
with an early model instrument.

The light sensitivity is due to your hitting one of the two diodes in the
head with light. They do a difference measurement between the two to cancel
out the temperature coefficient of the diode. The chopper in the box
switches between the two diodes (more or less).

Sounds like yours is in working condition. I'd hang on to it. They are not
as forgiving of high voltage AC as some devices but they are great for low
level signals.

    Enjoy!

        Bob Camp
        KB8TQ

----- Original Message -----
From: "Philip B Atchley" <[email protected]>
To: <[email protected]>
Sent: Friday, August 30, 2002 7:54 PM
Subject: [R-390] Millivac RF Voltmeter help

> Hello All.
> I have a test instrument here that I'd like to get a little information
> on.  First, let me mention that I have used many Laboratory RF
> instruments during past "RF careers" but have never run across this
> particular instrument.
>
> I did a web search on it but all I found were a couple units offered for
> sale with no other information.  I suspect it is rather old as it appears
> to be early solid state and I can hear the "Choppers" whine.  It's last
> inventory sticker is 1994 so I suspect it was pulled out of service
> around that time.
>
> All I know about it:
> It is a rack mount Millivac Industries Model MV-828AR RF MilliVoltmeter
> with "Type G probe".  The instrument has full scale ranges of 1mV to 3
> Volts full scale in 8 ranges.  It should be able to be read down to about
> .2mV or less.
>
> One interesting point.  The screw on probe tip is missing, though I
> believe the probe is electrically complete.  But on the 1mV range the
> instrument is very sensitive, even shining a FLASHLIGHT or other light on
> the end of the probe affects the meter ZERO (Discovered when I turned the
> bench light on).
>
> QUESTIONS:
> Anybody know the frequency range, input impedance etc of this unit?  Can
> this unit be used IN PLACE OF the HP Voltmeter/RF probe in the alignment
> of R-390A's etc?
>
> 73 de Phil  KO6BB
> Loving home provided for wayward Boatanchor Receivers
> [email protected]
> Merced, Central California
> 37.18N  120.29W  CM97sh
>
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