[TowerTalk] MFJ-259 as a signal generator

[Dick Green]

Where, exactly, do you attach the external null detector?

73, Dick, WC1M

-----Original Message-----
From: George Cutsogeorge <w2vjn@rosenet.net>
To: towertalk@contesting.com <towertalk@contesting.com>
Date: Tuesday, August 11, 1998 11:33 AM
Subject: Re: [TowerTalk] MFJ-259 as a signal generator


>
>I have tried a number of different ways to measure cable lengths for
>cutting stubs and phasing lines.  The best way is to use a network analyzer
>with a frequency counter, of course.  However, a decent job can be done
>with the 259 if an external null indicator is used.  The built in indicator
>shows a very broad null and is not adequate.  Various devices can be used
>as a detector with the 259 which will then enable resolution of 5 or 10
>kHz.  An oscilloscope with a low capacitance probe works quite well if it
>has adequate bandwidth.  Some type of RF voltmeter with a high impedance
>input such as the Boonton 92 works well.  The simplest thing to use is a
>DVM or VOM with a diode detector.  The old 1N34A with a 100K load and a
>0.01 coupling capacitor in front of a 200 mV scale works fine.  My
>preference is an analog type meter.  The limiting resolution is determined
>more by ones ability to tune the 259 acurately than anything.
>
>If you know what to look for, a decent network analyzer can be picked up at
>Dayton for a few dollars more than a 259.
>
>George
>w2vjn@rosenet.net
>
>
>
>
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