[sdiy] sniffing

[Czech Martin]

I bought a styro foam ball (will cover with alu foil) for E-field
and a toroid (some copper windings on it and alu foil
E-field shielding) for B-field (H-field).
Some early experiments show n x 10mV of AC line noise (50 Hz
fundamental, but much overtones) for the E-field (or
voltage, as J.H. pointed out) probe.
I try to build a jfet decoupling amp for the E-field
sensor, the other one will go into 50 Ohm scope input.

Interesting side effect: I tryed to put the scope ground clamp/tip
loop into a metal case in order to see the shielding effect...
I found out that the 107 MHz FM stuff will disappear if the loop
is far away from metal (table etc.). So I think that some capacitanc
is needed in order to tune the loop for this frequency.
Since I could'nt close the metal case completely, no shielding
was observed....

btw.: I learned that the Hameg 1505 scope has no 50 Ohm
termination as built in switch (which I thought it had,
bacause all the Tek scopes have it and I'm used to it).
So a clear reflection could be seen when using RG58
50 Ohm lines and a square wave generator.
You have to buy a special through-termination-resistor-BNC-thing
for a ridiculous price.
I then opted for a BNC-T and a BNC-50-Ohm termination piece,
that is ok, at 1/10 of the cost.

m.c.

-----Original Message-----
From: Grant Richter [mailto:grichter at asapnet.net]
Sent: Dienstag, 15. April 2003 19:22
To: jhaible; Czech Martin; Magnus Danielson
Cc: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] sniffing


If this appeals to you, you would probably enjoy this book:

"Listen to Radio Energy, Light and Sound"

by Calvin R. Graf
Howard W. Sams publisher 1978
ISBN 0-672-21525-X

Describes a simple audio amplifier with simple detector heads for
microwaves, earth fields, lots of stuff, including a shorted input
transducer for Barkhausen noise (discontinuous movements of mobile magnetic
boundaries between magnetic domains).

A great amateur scientist book, shows you how to use stuff you already know
in ways you might not have thought of.

Amazon.com shows it out of print:

http://www.amazon.com/exec/obidos/tg/detail/-/067221525X/qid=1050427058/sr=1
-4/ref=sr_1_4/002-1699855-4018446?v=glance&s=books

but worth looking for.