On Aug 13, 10:56 pm, Richard Clark wrote:
On Mon, 13 Aug 2007 13:09:09 -0700, Jim Lux
wrote:

Or, something like a 50k resistor into a 50
ohm load will be about 60 dB down,

Hi Jim,

Unlikely.

With parasitic capacitance at a meager 1pF across the 50K, its Z at
10MHz would compromise the attenuation presenting closer to 50 dB
down. At 1Ghz it would plunge like a rock. This, of course, presumes
a 1/4 watt resistor.

A better solution is to use surface mount resistors where the
parasitics are down at 100aF - but then you will have a frequency
dependant divider unless you can guarantee that the parasitic
capacitance of the 50 Ohm resistor is 100pF (sort of casts us back
into using a 1/4 watt resistor with a padding cap). At 1GHz, it is
not going to look like a trivial 50K load anymore.

100aF??? :-) X(100aF)/X(100pF) = 50k/50 ??? ;-) ;-)