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Re: [TowerTalk] Antenna SWR Measurement

Subject: Re: [TowerTalk] Antenna SWR Measurement
From: Jim Lux <>
Date: Sun, 03 Feb 2008 13:52:55 -0800
List-post: <>
> Now that I have some decent test gear, I would like to do some swept SWR
> measurements of several antennas I have. I have an HP 8350B, but would like
> to get some references to published articles on the subject.
> Can anyone point me to something useful I can use ?

HP/Agilent Ap notes?  There's one titled something like swept impedance 

The 8350 is a sweeper, so to do measurements you'll need some sort of 
reflectometer and detectors too.  A diode detector (or one of the new 
Analog Devices chips that has 90dB dynamic range) into a sound card or 
the $25 DATAQ data acquisition module might be a good combination.

You hook the sweep sync out from the generator into one input of the 
DATAQ, the forward detector output into another, the reverse detector 
into yet another, and run the sweeps.  Then, use an excel spreadsheet to 
  turn it all into useful numbers.

You might look at the probe for something like Larry Phipps's LP100 
power meter.  It has the forward and reverse bridge.

The 8350 has a GPIB/IEEE-488 interface, but most folks don't have a PC 
with a 488 interface.  There are ethernet or USB to 488 widgets, but 
they're in the several hundred dollar range.

The DATAQ is a real handy device for ham fooling around (and for $25, 
how can you go wrong)..

4 channels 10 bits, +/- 10V, serial port interface.   Lots and lots of 
uses.  1 LSB is

There's a $50 USB interface one, too, with 8 channels.

The other inexpensive data acqusition thing is to look for RS232 
interface multimeters on sale.  They're still in the 0.1% accuracy range 
as the DATAQ thing, but they have autoranging, etc. for lower level 
signals (e.g. the hundred millivolts from thermocouples, diode 
detectors, etc.)

Jim, W6RMK


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