[Elecraft] Receiver impedance?

[John Oppenheimer]

Hi Walter,

Elecraft receivers, I'm familar with (K2,K3,KX[23], use "Feedback
Amplifiers" for their Pre Amp. The Feedback Amplifiers are designed for
nominal 50 ohm input impedance. Fifty ohm input impedance is somewhat
import for operation of the receiver bandpass filter.

I'll assume detector input impedance, preAmp bypass, is also nominal 50
ohm impedance.

John KN5L

On 5/25/22 11:05 AM, Walter Underwood wrote:
> What is a typical input impedance for modern receivers, or specifically Elecraft receivers? 
> 
> I’m asking because antenna tuners are a frequent question on an SWL group I follow and I’m pretty sure that they are not needed for most situations. If the receiver input impedance is not 50 Ω, that is a big data point.
> 
> My belief is that receivers are generally medium or high impedance, depending on whether the first RF preamp is bipolar or FET, but either way, mostly voltage-oriented.
> 
> And, yes, I know that antenna tuners can be a LPF or HPF, depending on their configuration.