[Elecraft] Receiver impedance?

[a******@sbcglobal]

That’s nice to know. A long time ago I measured the input impedance of a Yaesu transceiver with a network analyzer. I looked for but couldn’t find my measured data but I remember it varied from band to band between 25 and 100 ohms, so within 2:1 VSWR. 

Al W6LX 

> On May 25, 2022, at 1:06 PM, Wayne Burdick <n6kr at elecraft.com> wrote:
> 
> All antenna-facing stages in our receivers are designed for a nominal 50 ohm input. All of the preamp stages incorporate feedback to ensure a predictable, constant input impedance.
> 
> 73,
> Wayne
> N6KR
> 
> 
>> On May 25, 2022, at 9:44 AM, John Oppenheimer <john at kn5l.net> wrote:
>> 
>> 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.
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