measuring cable loss
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.
A Pi attenuator will do it better.
73's
Richard Clark, KB7QHC
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