Re: Tracing receive signal for low signal

jim
 

K...Generally an RF generator output is "calibrated" with a termination connected ...Generator output 100 mv P/P open circuit ..when terminated into 50 ohm ..output "split"  half absorbed by generator, half by termination thus actual reading 50 mV ...

with 50 mV open circuit through 50 ohm generator + 1200 through test probe = 1250 ohm  ...then terminated into 50 ohm

voltage drop across 1250 ohm in series with 50 ohm termination ...roughly 25:1 means 1/25 of the signal is dropped across load, 24/25 dropped across generator/test lead
 
1/25 of 50 mV is about 2 mV  ...

You would do better with a random piece of coax and a blocking capicitor from the signal generator ...No coax?  use a twisted wire pair ...maybe noisier, but lots less loss ..short (2 - 3 feet of wire/coax)

Jim

On Saturday, January 12, 2019, 8:17:13 AM PST, Dave Space <davesspacebar@...> wrote:


Thanks for all the info.  Ok trying to see if I got this. It does look like loading.

1x probe is 1.2k
10x probe is 8.9 Mohms

I checked the probe directly outputting 50mv verified 50mv through a .01uF blocking cap @ 11.996MHZ
I put the generator into tp17 and measured at tp17 and I would say less than 5mv p-p was being read from what I could tell.

I wasn't understanding if there is a way to now match this better or not?

Thanks

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