LF Stuff

Brooke Clarke brooke at pacific.net
Tue Sep 30 14:20:32 CDT 2003


I had a look at you web page for LF and have some comments.

LF Impedance "AMRAD Presentation on LF Impedance Measurement"
The method in the paper is very similar to the one in HP patents 
5,345,182 and 5,463,323. I think these were for the 4191A Impedance 
Analyzer. A classical bridge has the measuring instrument connected with 
both ends above ground and that's not so good for RF measurements, so a 
balun can be used. . . .

I have been making some measurements on how the characteristic impedance 
of a transmission line varies with frequency when the frequency is below 
the line corner frequency. To make these measurements in the 10 Hz to 
500 kHz range I have been using the HP/Agilent 4395A Network Analyzer 
and the Z Transformation method. See:

The Z transformation method measures the DUT connected in series between 
the center conductors of a normal network analyzer test setup , like an 
S21 measurement. Then the analyzer does the math to convert the result 
into impedance and can be displayed as Lin Mag, Log Mag, phase, real or 
imaginary. The beauty of this method is that it can be used over the 
full 10 Hz to 500 MHz range of the 4395A. Note that the 43961A Impedance 
test kit only works above 100 kHz. The 43961A uses the technology of the 
above patents. It may be possible to home brew a version of the 43961A 
that would work lower in frequency.

The Z Transformation method is what's used in the HP/Agilent E5100 
series High Speed Network Analyzers that are specifically designed for 
crystal characterization.

PS the spiral graphic in this paper takes a very long time to download. 
A plain white background pdf version would make net viewing a lot less 

Larry Kayser’s,, PIC Program .ASM file
What does this program do?

Low Pass Filter?
The reason I Was on this page was to find details of a low pass filter 
to use with your active LF antenna which I now have.
Have their been any updates on the power supply to reduce the line 
conducted noise that I found with the original design?


Brooke Clarke, N6GCE

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