E/H Field probe for scope
E/H Field probe for scope
(OP)
Hi,
I am interested in trying a simple near field probe like mentioned in thread247-149185: probing for noise or in Link
I have a 300MHz Scope with FFT functions, but no spectrum analyzer.
My main question goes for input impedance of the scope (1G), shoud I get or make a 50Ohm (probe and cable to scope) to 1G impedance matcher? any idea of previous work?
As you may think at this point of the post, I am quite lost in the HF world, but think that a probe just to make comparative measurements in different positions can be useful for us for a initial assesment previous to talk with the guru guys.
We work specially with equipment such us thyristor rectifiers and PWM inverters, so noise and problems that sometimes we have usually go from a few kHz to no so many MHz
Thanks!
RE: E/H Field probe for scope
This advice assumes that your probe cable length is sufficiently short (compared to the wavelength of the signal) that you can avoid having confusing standing waves in the test gear. In other words, for a typical three or six foot long cable, as you get into VHF, you'd best start worrying about matching again.
RE: E/H Field probe for scope
in case need of matching, what is the most sensible method for a big impedance change like this?
RE: E/H Field probe for scope
In any case, just put a load at the 'scope end of the cable. Many 'scopes will provide this as a setting, or just use a suitable resistor. An attenuator can also be pressed into this role.
Don't bother unless you really need it.
RE: E/H Field probe for scope
good luck,
AC8V