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[Amps] 8405a setup question?

To: amps <>
Subject: [Amps] 8405a setup question?
From: Dan Sawyer <>
Date: Mon, 19 Dec 2005 20:08:56 -0800
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All, my 8405a is set up and almost perfectly calibrated. Due to a 
difference in diodes between the probes the sampling efficiency on 
channel B is just readable less 'efficient' then channel A. The A 
channel is very close to perfect and B has a 2% or so rounded shoulder. 
This has an effect but it is limited.

Now my question. An oscillator is setup to feed a tee. To calibrate the 
8405a both legs of the tee were set up the same, an identical coupler 
and a 50 Ohm terminator on each. The 8405a probes were connected to the 
coupler ports. The 8405a was then set to zero phase reading on the 6 
degree scale.

Then on one leg the 50 Ohm terminator was removed and replaced with a 2 
meter loaded dipole. The frequency was then adjusted to read zero phase. 
I concluded this was the zero reactance of the antenna. Is there 
anything in error about this conclusion?

At this point the coupler connected to the antenna reads 6 db higher 
then the coupler connected to the 50 Ohm terminator. How can the 
impedance of the antenna be calculated? A first guess would be about 12 
Ohms, 50 divided by 4. This is above the number calculated for the 
antenna, but it resting on a less the perfect 1 square foot plate for a 

The tee is not a power splitter. What are the possible interference 
effects? Should the tee be replaced with a splitter?

Thanks - Dan
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