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how to AC couple

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notwist

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i have a signal i want to input into a spectrum analyzer, but i have to AC couple this signal to avoid damaging the analyzer. How can I AC couple this signal? The signal is being generated by a TIMS module so i can just connect the cable to the analyzer but how do I ac couple it?

Thanks in advance.
 
Overclocked said:
I think the value Oscilloscopes use is 10pF Or So.

Er, no.

My scope (Telequipment D75) uses 100nF.

You may be thinking of the parasitic parallel capacitance at the input connector, 29 pF in my scope.

JimB
 
So why would you DC couple an RF device?.

Or do you mean it has a 50 ohm or 75 ohm load directly across the socket, and (presumably) capacitor coupled from that?.
 
Well, you have a good point. What I mean is that it looks like a 50 ohm resistor to anything connecting to it. Ironically, the signal processing that follows does indeed have a high-pass filter in most cases, so you don't get the benefit of DC coupling on the display.
 
And of course a transformer can be used to AC couple a signal to a device. Not as common as a cap because of costs but has an advantage of step up or step down voltage ratio or even center-tapped output for balanced signal processing.


Lefty
 
Some HP spectrum analyzer's inputs will be damaged by having DC applied to the input. Says it right on the unit in red letters. ;)
 
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