Tony Berg <tony.w1ot@gmail.com> wrote :
> External receiver calibrators are available as Elecraft kits XG1 and
> XG2. They provide an output of either 50uV or 1uV into a 50-ohm
> resistive load. These levels correspond to S9 and S3 1/3 per the IARU
> Region 1 recommended standard. But how many receivers provide a 50-ohm
> resistive input (without an input attenuator switched in)?
Receiver's input impedance is irrelevant for sensitivity (and noise figure)
measurements, which are defined in terms of the "available power" from the
generator. The generator output impedance should be close to 50 Ohms.
Receiver input impedance can be very different from 50 Ohms.
73,
Sinisa YT1NT, VE3EA
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