[R-390] Measuring Sensitivity - Ramblings...

[n4buq at knology.net]

On Sun, 11 Mar 2007 21:47:28 -0600, "Barry" <n4buq at knology.net> wrote :

> Having some 150-ohm and 1-ohm 1% resistors, I made a 100:1 voltage divider
> as discussed.  This definitely makes measuring the sensitivity an easier
> task.  With this, I am seeing from 0.5uV to 1.5uV on the bands I tested.  
I
> need, though, to make a sniffer and see if some of what I'm seeing may be
> attributable to leakage.  Hopefully, there isn't too much leakage and 
these
> figures are pretty close to accurate.  By the way, I divided the observed
> output level by 200 to get these figures.  If it is really only a factor 
of
> 100, then these figures are 1/2 what they should be.  I need to find out
> which way to do this.  Maybe I can measure it at a higher voltage level 
with
> my VTVM to know which is correct?

I did some more testing last night.  I cranked the generator down to the 
lowest frequency setting (15kc) and measured the output with my Fluke DVM.  
Feeding the 100mV output into my 50.5-ohm divider, it measured right at 
50mV so it appears dividing by 200 is the correct thing to do here.

Doing the same thing using the 10mV setting (using the 40-ohm series 
resistance adapter) into 50.5 ohms also showed 5mV (or something pretty 
close to that as I think my DVM was getting a bit flaky at those voltage 
and frequency values).  At least I now know what the output voltages are at 
the various settings (or at least something pretty close to what they 
should be).

Now to house the divider in something with proper connectors and make it 
convenient to use.

Thanks for listening...

Barry - N4BUQ