[R-390] URM-25D recap.

Mon, 24 Jun 2002 14:15:30 -0400

Yes, an "RF" voltmeter is required here. The signal IS alternating current,
not DC. All AC voltmeters have a frequency passband. The typical "panel"
meter, used to measure, say, 0 to 150 volts AC will be accurate only at the
60 Hz AC power line frequency. A voltmeter used to measure, say 10 Mhz, must
have a passband going up to at least that frequency. An excellent meter for
this purpose is the Hewlett Packard model 410-C, which goes up to ( I
think ) around 700 Mhz. The older ( and much cheaper ) model 410-B will work
just fine too, if you can find one that still works properly.
Chuck N1LNH
-----Original Message-----
From: Jim Temple <[email protected]>
To: [email protected] <[email protected]>
Date: Monday, June 24, 2002 12:22 PM
Subject: [R-390] URM-25D recap.


>Hello to the list,
>
>I picked up a URM-25D at Dayton this year.  This unit had the typical loss
>of modulation described in many of the messages posted in the archives.
>Upon inspection, ALL the large paper caps located on the modulation board
>were physcially wet with a slick discharge from the innards of the caps.
So
>I obtained replacements and installed new caps as recommended in the
>archives.  I even broke open the case and replaced all the similar paper
>caps located on the various internal modules, which were also wet with a
>discharge.  Upon reassembly, all functions work as intended, and after a
few
>hours warm up, the stability of the unit is rock solid.  Now on to my
>question.
>
>Question:
>
>In the lists experience, is a recalibration necessary after recapping this
>unit?  The frequency alignment seems to be quite good.  But I am uncertain
>about the calibration of the voltmeter function.  I have the Navy manual
for
>the URM-25D, but am interested in tips on calibrating the voltmeter
>function.  For instance, 2.0 volts are mentioned as an approximate value at
>the RF output jack.  Is a RF voltmeter required for this measurement?  Is
>this voltage a DC voltage?  Any help here?
>
>Thanks for your past support.
>
>Jim
>
>
>
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