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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