We have this setting:
...--(56ohm)----(47ohm)----(47ohm)----(RG58/U to spectrum analyzer) | | (3.3ohm) | | --- ---
47ohm, 47ohm and grounded 3.3ohm resistors form the three resistor attenuator. Attenuator attenuates the circuit output delivered to 56ohm load. Now what is the output impedance of attenuator?? and why? (asuming that RG58/U coaxial cable has an impedance of 50ohm)
Is the 3.3 to ground between the two 47 ohm resistors or the 56 and the first 47 ohm resistors?
Tom
yes, 3.3 goes to ground btw the two 47 ohm resistors.
this is a -36dB attenuator (T-type) schematics (with a Z transforming
2:1 too) with approx. 50 ohm output impedance. (& normally approx. 100 ohm input Z ). Since imedance of spectrum Anal. is 50 ohm & has connected the last R of 47 ohm in series, its input gets -6dB signal (half voltage of it= matching impedance) compared to the taken point on 3,3 ohm resistor (-30dB); so on the Analizer you get of TL -36dB attenuated signal (approx. only of 1/64 part of the voltage of main input signal with 50ohm matched inpedance /Z/ with Spec.Anal.) ...
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Regards, SPAJKY ®
& visit my site @ http://www.spajky.vze.com
"Tualatin OC-ed / BX-Slot1 / inaudible setup!"
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